Table of Contents

1. Reproduction

   1. Pollination

   2. Plant sexual systems

   3. Seed dispersal

2. Survival under low-nutrient conditions

3. Survival in hot deserts

Reproduction

Pollination

Introduction

Sedentariness: crux of being a plant. It needs to be able to manipulate the environment.

Plants are connected to the ground. Organisms need to manipulate the environment to do things for them. To get reproduction done.

Quantity and quality: the more, the better (darwinian fitness), helps avoid inbreeding. Yes flowers want to produce more seeds, but their behaviour is determined based on quantity and quality in a trade-off.

Quantity: single bout of reproduction. Semelparous plants. How they achieve it:

• Either reproduce once in their life and die, or time and time again over lifespan.

• Semelparous plants only produce once. In summer they germinate and invest into themselves. One bout of reproduction and then they just die. Dire to reproduce.

• Biennial: plant is around with just leaves through a year, they produce photosynthetic sugars, store sugar in organs. As year 2 roles around, they take stored nutrients and produce fluorescence.

• Perennial: many growing seasons. Guy hangs around every year, never flowering, builds carbon blocks/reserves for years and produces the giant inflorescence and then dies.

In all above cases: once it reproduces → it dies.

Iteroparous plants: repeated reproduction. All trees are this. Produce multiple times a year. Two experimental fields of white clover grow way worse with inbreeding. How do they maximize the quality?

Inbreeding depression: white clover example. the reduced biological fitness that has the potential to result from inbreeding.

Female quality control: Females have a much higher cost to reproduction. Style competition. Increases the quality of offspring - good genes.

Style competition: with 5 pollen grains, how many are needed to fertilize 2 eggs. The style is the selective race track. Stigma is the top, style is the middle tube section, and the ovary (few eggs) are at the bottom of the track. Female wants many pollen grains to land and compete so only the fastest growing will pollenate the egg cells. Faster it grows, more likely to have good genes.

Need a pollen grain for every ovary. The more pollen, the more competition.

Evolution of style: increasing accommodation for race. Primitive angiosperm had enough space for pollen cubes, stigma was shorter, multiple tracks to ovaries. In more modern/advanced angiosperm, it has a bigger stigma, one tunnel connecting stigmatic surface to one ovary (higher competition)

More pollen grains → faster pollen tube growth. Mean tube length per unit time (growth speed) and pollen tube per style has a positive correlation. When there is less pollen tubes per style, they grow slower. More advanced angiosperms are better because they have more pollen tubes per style.

Higher pollen competition → better offspring quality?

Pollen from bee plants are stickier. In an experiment with single-visit flowers and open pollinated flowers, open pollinated flowers had more number of pollen grains deposited. The open pollinated species had a significantly faster speed to emerge and grow from seedling and to first leaf.

More pollen tubes per style = higher speed of pollen tube growth (better male quality)

Flowers are not passive. Females facing higher reproduction pick higher quality seeds.

Symbiosis between flowers and pollinators

SYMBIOTIC RELATIONSHIPS

Nectar

Currency of the exchange is about plants giving something in return for fertilization purposes.

Nectar: high-energy food reward. Predominantly for adults like worker bees. Nectar is turned into honey. Important for adult animals. Worker bees, butterflies, hawk moth. If you’re done growing, you can fuel on carbs easily.

Nectar is produced in nectaries. Insects have to work hard to get access to these nectaries. Holes look like stomata, but are glands that use the nectar. They got much deeper as time went on.

Nectar spur: located at very base of flower, gotta pass through a bunch to get your hit. Hollow organ that secretes nectar in some flowers.

Nectar as a currency in symbiotic coevolution. Plants may maximize its lifetime reproductive success by adjusting nectar quality and composition.

Primary compounds: energy pollinators are after this. Made up of sucrose, glucose, and fructose

Secondary compounds: toxins keep unsuitable species out (nectar robbers, microbes) with toxins, smells, tastes, or attractants that make them irresistible.

No nectar: pollinators visit it cuz it’s sexy when there’s nothing there (cheaters)

Nectar is adapted to pollinator needs. Different types of sugar and concentrations. Sucrose, fructose, glucose, hexose.

3 different classes, they only look at fraction of sucrose in the nectar. Hummingbirds like sucrose, butterfly likes it too. Bats don’t really like it.

Concentration of which sugar is in the liquid. Lepidoptera like more concentrated, while others like more runny.

Lepidoptera uses primarily sucrose, nectar sugar concentration is high (viscous), very fragrant.

Pollen

Pollen is protein rich, and important growing bodies (of bees). Pollen is predominantly consumed by juveniles. There is different pollens from different plants, not created equally.

Pollen quality: plants do the math. A lot of pollen is pollinator reward, from pollen is for fertilization, and a lot is lost in translation. Pollen collected on the body of the bees, hind legs, etc. Pollen baskets are on the outside of the hind leg, along with a pollen press (the front of the joint). A lot of pollen is not brought into the hive.

Extra pollen is dedicated as reward. Commonly, 1 set of anthers, bees pick it up, some pollen is food, some is fertilize, can’t tell the fraction. Yellow - feeding anthers (reward), red - pollinating anthers (fertilization, bees don’t see, it’s cryptic).

Anthers: typically pop out colour-wise in comparison to petals, the pollinating ones are inconspicuous, the pollen from conspicuous ones is wasted in terms of flower fertilization.

Pollinators prefer flowers with feeding anthers, not pollinating anthers.

An experiment had 3 treatments, both classes of anthers. Bees don’t care about pollinating answers, they recognized there was no food.

• Flowers with both feeding and pollinating anthers, and flowers with just feeding anthers had about the same amount of frequency of visits.

• Flowers with just pollinating anthers were visited far less than the others.

Resin

Organs that produce resin are called a resin ring. Resin glands are in flowers. They are sticky, hydrophobic, some bees collect it - some solitary bees construct walls of brood chambers with it.

Contains chemical properties (antifungal, antibacteria), reduces risk of disease and parasite transmission in brood chambers, collected by solitary female bees.

Use of resin: increases structural nest stability, and defense (sealing). Decreases disease and parasites, and fungal and bacterial growth.

Collected by some female bees.

Fragrance

Lots of flowers smell good to attract, and some species collect it.

Collected goods: scent collection by some male bees.

Female euglossine bees prefer fragrant males. Males go collect fragrances (and inadvertently pollinate flowers. Bees scrape off smelly oil, get the sticky oil fragrence of orchids in hind legs (oil container).

Collected by some male bees.

Frequency of all: Resin < Fragrance < Nectar < Pollen

They all produce different flower morphologies

PARASITIC RELATIONSHIPS

Cheating plants:

Why cheat? Cheating costs less energy of carbon building blocks. They get the job done.

For average cheating, it has to be surrounded by other honest species. Bees will leave if they’re all cheaters. When they’re all cheaters, there is limited or no reward. Cost of reproduction is lower, but the success of cheating is lower when surrounded by cheaters.

Cheating flowers look like honest species.

Orchids are often cheating, not giving up their nectar or pollen or whatever it is. Proportion of cheaters visited:

There is no reward. Cheating doesn’t need to be rare, if they’re irresistible. True in sexually deceptive flowers. Horny males can’t get the message, they just keep coming back.

Hammerhead orchid: fake female wasp (head, torso, fur). Hinge between female dummy and rest of flower. Pollen packages (pollinia). Male wasps at half their fertility when they’re around.

Fake insect on plant, meant to mimic a female. The male will attack, get glued and will bump against the pollen trying to escape. It will fly around with the pollen packages. Uses a very potent fake scent. Female crawls up on the plant, disperse a microgram of pheromone to attract the male, while the plant disperses 10 x the amount of pheromones. Whole package is very irresistable.

Attractiveness of Andrena bees: Female ophrys flower > extract of flower > female bee with smell > female bee without smell

Sexual deception by flowers impersonating female wasps. Hinge goes back and forth, glues pollen onto back as it hits back and forth. Will then go a deposit pollen packages, keep going around.

Looking at the scent and shape affect of the plant. Using an odourless dummy, the flies attracted to it the least, then smelly female, then just the pheromone, then the plants level of pheromone with just the flower and deceptive shape.

Orchids each have their own hooked bee species. Quite good distinction between species in hydrocarbon odor. There species are different in non-hydrocarbon. They are so distinct amongst closely related species. Through evolution, they have been able to match very closely, each on one species of bee. Orchids so convincing, the bee ejaculated

Even though the hydrocarbons alone and the non-hydrocarbons alone do not completely differentiate between the three species of orchids, taken together they result in the three orchid species attracting three different species of bees

The cost of sexually deceptive orchid to male wasps: they don’t have enough sex in an ecosystem with no orchids - have much higher ejaculate size. Clear evidence of parasitic relationship

Sexually deceptive flowers and horny male insects are extremely irresistible. Highly evolved pollination service (1:1) relationship: not cheap but very effective =/= cheap cheater in a sea of honest plants

Flowers as traps

Some cheating flowers are traps. Deceptive fungus-scented smell. Outer structure (pulpit), inner structure (jack). Jack produces a pheromone that smells like a fungus. Mamas want to lay eggs there. Purely male and female plants. Jack in the pulpit need to make their pollen flown over to females.

The males have no fungus, they get loaded up and go search for female. No exit hole for females. Too hard to crawl out, and they die.

Cheating pollinators

Sometimes pollinators are too big to enter a flower so they drill holes and rob nectar. Construction of the flower is too big to get inside, so they start drilling holes into flowers. Get the nectar without getting the job done. Easier to pre-drill holes. Access to nectar through hole often easier than to crawl in the legit way.

Some insects species cheat more than others. 7 species of bumblebees. 4 categories (2 legitimate was to collect pollen, 2 robbing ways - primary and secondary). Primary robbing: drilled a hole. Secondary robbing: there was already a hole drilled.

Any robbing results in no fertilization and is a net loss for the plant. Wurflenii couldn’t stop robbing.

Primary robbers increase secondary robbers. Effect on secondary, normally honest flower visitors. Not a primary robber (no drilling of holes).

What percent of flowers that have been drilled and what percent of honey bees interact with them. About 50% of flowers have been frilled, majority of bees will use it in an illegitimate way.

Nectar robbing decreases seed production.

Pollination syndromes

BIOTIC POLLINATION SYNDROMES

Narrowing amount of possible pollinators (narrowing the syndrome), because the pollinators like it, they’ll come back and deliver without visiting another plant. There is less wrong pollen export. Less of pollen A going to species B (less waste of male resources). Less B taking in import (less waste of female resources). Faithful pollination is real from adaptation of body plan. Once animal has learned to service a plant, it wastes less resources for the plant and animals. Pollinator gets its desired goods easier/faster through adaptation.

Insect evolution and angiosperm radiation. Similar giant bump in species (radiation). Angiosperms came in swinging after. Today, majority of plants on earth are out here. Insect evolution was very plant driven.

Angiosperms started diversifying in cretaceous. Angiosperms youngest and most diverse. Radiation of many insect groups. The radiation of flies and bees occured in parallel to the evolution of angiosperms.

Bees are the most important pollinator group.

Nectar: adapted to pollinator needs. 111 species of bromeliads.

Pollination syndromes vs. colours. We don’t have UV receptors. One specializes in UV. One specializes in green. Construct flowers with green is stupid - bee pollinated flowers enters UV - bee flowers are not read.

Hummingbirds enjoy a red coloured flower. But it is not because they see ted the best, they actually only barely see red. Bird-pollinated flowers are using the color least useful to bees. Hummingbirds have 4 photoreceptors, good vision across. Stronger red than bees, they see better in orange and red better than bees. Bees are so dominant on blue and yellow, so hummingbirds don’t bother.

Monarchs learned to prefer orange because they avoid bee colours and they’re really well in range. However, monarch butterflies can easily be trained to prefer blue and purple → new colours associated with food. Innate preference of orange, trained on blue or purple. Bees and butterflies both like nectar compared to other species. Nectar guides are present in bee and butterfly flowers.

Nectar guides: lines pointing towards nectar. Effects handling time and visitation by bees. Time for first legitimate land with nectar guides are much faster than those without (experimental). Nectar guides increase flower use and efficiency

Bees learn to handle flowers better over time. Learning gives faster handling time and better accuracy.

Bees: faster access to more reward, fewer wasted resources. Bright white and yellow contrast, yummers, nectar guides, radially symmetric flower.

Flowers: more accurate pollen pickup and delivery, fewer wasted resources. Jewelweed were handled with more accuracy based on how many times it was visited.

Bats

Bats don’t care about colour so they can engage with many different flowers at night. During the day they stick with purple.

Bat pollinator syndromes: Big, bowl-shaped sturdy flowers (fit big faces of bats → long tongues). Odor emitted at night. Lots of pollen, lots of nectar hidden at the bottom. Pale flower colours.

Miscellaneous

Small mammals pollinate things. A mouse is a legitimate pollinator (not just a visitor). Flowers close to the ground are visited by mice.

• Experiment: 3 different treatments; the control (bunch of flowers open), 2 cases with encapsulated flowers with a veil (rough mesh where mice can’t visit, but flies can, and another where veil excludes both). Allowing mice in, allowed for lots of seeds produced. 73.5 : 3.3 : 0.

Cockroach pollination: Many studies claim certain things are main pollinators, but don’t prove it. Experimental tests are needed.

Evolution of biotic pollination syndromes:

All these flowers evolved through natural selection, and random rate of mutation can result in sets of adaptations, where they adapt to a specific pollinator. Works through a series of random mutations.

There can be a switch between syndromes. Certain characteristics are maintained by very few genes (change fast and large). Researchers manipulated smell of flower, changing pollinator from wasp to carrion fly. Smells are governed by few genes. Without sulphur, carrion flies don’t care, the only thing that got them to care was the scent change, but when added, they were obsessed with the wasp-flower.

Transition between different bee pollinators: different bees grow fat legs to collect. There are 48 species of Dalechampia and have pollen, resin or fragrance attracters. Relatively early on, some flowers adapted to be pollinated by male bees. Some species which evolved later are equivocal. Even though we think of systems being specific, mutation alone, results in a switch in pollination system.

Different types of sugar concentrations can change pollinators. In closely related groups, mutation is enough to have them adapt to very different pollinators.

Dalenchampia flowers: exclusively pollinated by bees. Different bees which collect different rewards. Switch between pollinators has happened many times evolutionally.

ABIOTIC POLLINATION SYNDROMES

Abiotic pollination is undirected, can occur through wind and water and others. 10% of plants are wind pollinated, 18% of plant families contain wind-pollinated species. Wind pollination is more common in open vegetation (less trees), at high latitude and altitude, in dry environments, and in island floras.

Conifers releasing pollen into air at crazy rates can look like a smoke show.

Typically, female reproductive origin of wind-pollination. Highly branched, like a feather. Stigma is very long. Corn, every kernel is connected to an individual silk → stigma is sticking out, trying to release and get pollen in the space in the air space. From anthers, pollen is release in the air. Present in 10% of flowering plants, 18% of all families of flowering plants have a wind-pollinated species.

In many areas, animals can’t survive easily, so animal-pollination is too low. Many animal pollinators may not have established in the environment. Ecosystem typically does not have continuous forest cover.

Wind is non-directional and thus not very efficient with pollination. There needs to be an incredible surplus of pollen. Cheap on flowers though because they do not need to invest in colour or nectar.

If wind pollinated flowers are completely unselective, their stigmatic pollen load will mirror closely pollen composition of surrounding air. Feathery stigma, long and branched styles/stigma. Traditionally, wind pollination is not very effective. Filter out from environment. Up concentration of R. filformis → preferentially pick the pollen, doesn’t just get smothered in the wrong pollen.

Specific pollen-stigma compatibility depends on the shape of the pollen grains and the types of stigmatic surfaces of plant. They work like lock key

Pollination syndromes: a myth?

Low pollinator specificity is quite common. Few plant species specialize on pollinators. Many have low pollinator specificity - are pollinator systems overrated?

Presence of angiosperms in Illinois. How many visitors are visiting flower? Small number of visitors, only few visit a single species, where as visited by more than 48, it has a loose connection to it's pollinator (lots)

Yes some species in illinois are visited by only one pollinator, but lots of plants (25%) are visited by more than 48 pollinators. Very low specificity.

Parameters per pollinator group fed into computer model. A close adaptation connect to plant. Produced a 3D model, separating different pollinator syndromes. Look at more characteristics. 10 animal groups were mapped into different areas of a space. Clouds represent pollinator (dot is a species of plant), they all kinda group together.

The above formed the basis of expected parameter space anywhere globally, if they are a strong thing. Supports segregation of syndromes. Looked at 4 species rich areas.

Most of the selected species do not overlap, pollination syndromes are overrated and are not some absolute crazy thing. 2 lines of evidence support that it is not a worldwide approach.

HOWEVER, different morphologies exist in closely related species. 4 species of morning glories overlap in habitat but have very different morphology. Pollinator specificity? Colour and shape are very suggestive in what visits them. The little pictures are what we expect to visit it. Hummingbirds see the big corolla.

Pollinator specificity is not perfect, but it’s also not nothing. Significant fraction of morning glories pollinators were butterflies. Doesn’t just get one group, but it does get more faithful visitors.

Separation helped by slightly staggered flowering time.

Morphology selected, favoured by natural selection.

Helps imperfect state, pollination works. Concert of many traits needed. Trait states can be imperfect, as long as flowering is staggered, plant diversity is within a limited plot.

Mallows: special stigma and anther modification for fertilization. The anthers are inserted in close proximity to the stigma, allowing for selfing as a last resort when pollinators have not visited during most of the fertile period of the stigma.

Generalist pollination

Generalists benefit → less risk of general pollination failure. Easier to colonize new areas. Trying to be pollinated by a narrow group of plants may suffer without a specific species, but generalists can have others ready to help out. Generalists colonize new areas better.

Traits: Average nectar concentration. Many flowers from large landing platform for any insect. Elderberry, goldenrod, Queen Anne’s lace. Coltsfoot. Tiny flowers, landing platform.

In NE North America, a lot of plant species are generalists. More full generalists. Rely on a very narrow range of animals to do their job.

Adaptive Selfing

Produces poor quality offspring. Plants use selfing on a backup system.

Delayed selfing in ageing flowers. Young flower - no selfing (stigma are straight out, not folding back to anthers at all. Ageing flower can tell if there’s any pollen or stigma available, the bend back towards anthers. Old flowers start slefing (completely attached at stigma and anther).

Selfing within an individual - outcrossed flowers are at peak production in early spring, then selfed flowers come out in late spring, when seeds are not disperse. Seeds made in summer, they may continue to self. This is a high quality seed vs. a backup seed. Selfed seeds insert themselves into soil besides parent. Plants usually try hard to avoid selfing.

Self compatible species are able to purge deleterious alleles more effectively than self-incompatible species.

Plant sexual systems

Monecious: Plants produce 2 types of flowers. Both sexes on same plant but nor same flower. M, F. 17%.

2% - gynodioecious, androdioecious, gynomonoecious, andromonoecious.

Gynomonoecy: a M+F flower, and a female only flower

Andromonoecy: M+F flower, and a male only flower.

Gynodioecy: Female only plant, M+F only plant.

Androdioecy: Male only plant, M+F only plant

Dioecy: 6% of angiosperms. Plants each have one sex, populations have two sex. Risky way of reproduction. Allows unisexual flowers to fully specialize on needs and gender potential. 100% outcrossing. 100% specialization on M or F needs. Selfing is possible for all plants except this kind.

Hermaphroditism: 75% of angiosperms. Less risky. Anthers rub on stigma. Sexual conflict in terms of advertising. Mechanical issues and inbreeding depression through selfing. M+F on a flower.

• Alleviate mechanical conflict: de-crowd the flower. Spatial separation of M and F. They put space between things on the flower to avoid sexual conflict (selfing).

• Temporal separation of M and F can help eliviate these issues → M phase more closed, F phase more open.

Modern view on spatial and temporal separation: Decrease mechanical interences of M and F function. Increase M and F function of pollen pick up and delivery.

Sexual interests are different, so there will be different investments into advertisement. Inbreeding, pollen export, resource allocation (in limiting conditions). Being a hermaphrodite sets up sexes in conflict because shorter flower visit, shorter per individual is good for female, but the opposite is good for male.

Idealized way hermaphrodites work is in a middle ground of female function (small flower, fragrance and nectar volume), and male function (big flower, fragrance and nectar volume).

Selfing is plagued by inbreeding depression. What do they need to avoid? Some degree of self incompatibility. Majority have some level of incompatibility. Spatial and temporal separation is root of incompatibile species. Throwing in separation doesn’t work anymore. Wide range of selfing in many-flowered plants, lowered in single-flowered plants.

Plant fertilization is highly complex manipulation of biotic and abiotic environment.

Self incompatibility:

Early-acting SI: pollen from own genes. Compatible pollen, entering straight, while rejected pollen is curled and plugging stigmatic surface.

Intermediated acting SI: Tissue of female structure recognizes genes of pollen, stopping tube growth two avoid selfing. Stylar plugging around incompatible pollen tubes (curling). Recognized by tissue.

Late-acting SI: Pollen grows all the way, ovule recognizes pollen tube, doesn’t fertilize.

Strength of self-(in)compatibility. Not all-or-nothing. Nearly 50% of angiosperms: some self compatibility SC.

SI best way to reject your own pollen. It is highly complex genetically and biochemically. Independent evolution across the angiosperm tree of life.

Spatial separation of sexual organs within flowers

Sexes are active at the same time, but organs are too far from each other, and there is a low chance of pollen every tom make it into (a next individuals stigma).

Issue with hermaphroditic flowers being on same flower. Partial overlap of sex inflorescence can be another issue.

Temporal separation of sexual organs within flowers

M-phase closed, F phase open. Either can come first.

Issue with monoecy, where simultaneous flowering of M & F in one inflorescence. Partial overlap of sex inflorescence can be another issue.

Optimization of fitness

Male aim is for most quantity (pollen), while females aim for most quality (good offspring). Different goals can create potential conflicts.

Decrease in interference of M and F can help lower issues. Talked about above with decrowding and stuff.

Spatial separation has a decrease in gender interference. Increase in pollen pickup and delivery. Decrease in stigmatic pollen clogging.

M phase: anthers straight, just opened, stigma not active, physical/temporal distance.

F phase: Anthers empty, older flower, styles longer/F more optimized.

M fitness: 1000s of pollen, many visits necessary to empty anthers. Biggest 70% of the time. Easier to see, lures pollinators to come pick up pollen. Smell more. More nectar (4x) as an incentive to pollinators..

F fitness: 1 to hundreds of eggs. One or few visits necessary for full seed sets. Biggest 25% of the time. Cut cost on odor to make egg bigger. Less nectar.

Unisexual flowers optimize, while hermaphroditic flowers compromise (jack of all trades).

Seed Dispersal

There are two mobile life cycle phases of plants. From haploid vs diploid perspective. We’ve talked about haploid males picking up and depositing on a stigma. Purple has a second life stage with diploid seed.

Flowering in M is more important than F, has higher advertisement, protein in pollen. Overall reproduction cost is much higher in females. Seeds and berries are important and expensive.

Variation in pollen verses seed size - While pollen grains are different, they’re all tiny. All microscopical. Whereas seeds are way larger and bigger in variation. Huge diversity of seeds compared to male pollen grains.

Seed size varies because of life history traits between species. Different ecological conditions/habitats between species.

Life history traits of types of plants wo effect seed size in a way.

Non-wood annual herbs < non-woody perennial herbs < woody shrubs < woody trees.

Effect of key life history traits on seed size os the living conditions. What is the average annual temperature, does it rain, is it more beneficial overall to photosynthesize. If it’s dry, this is bad. Positive relationship with productivity and seed size. Lot’s of scattering. Net primary productivity is positively correlated to seed mass (not strong though).

Reasons for or against seed dispersal

Escape hypothesis

The more seeds are present, the more likely they are to die. Reasons why they’re more likely to die is because organisms who like to feed pull up and kill them all.

Mortality and density are strongly correlated. Density-dependent mortality.

Agents of mortality: predators, resource limitation (competition).

Common.

Colonization hypothesis

Chance for offspring to occupy unpredictably good sites. Successional communities (ecosystems in change). Typical for r-selected species (disturbed sites, weeds).

Trees which produce cheapest trees. Tiny, hairs, travel far, they produce so many seeds to hit anywhere. Very few establish. Cottonwood, trembling aspen.

Common.

Directed seed dispersal

Non-random reach for a particular, predictably suitable places for establishment and growth. Good sites are more stable and plant can get seed to good sites.

Ants carry seeds with elaiosomes to nests, remove elaiosomes for food, and discard intact seeds on trash pile (mound) next to nests (good site).

If you are a large seedling you're more likely to be fit, so you'd think yeah the bigger the better.

Seedlings growing on the mound

The smallest class, least fit, were predominately not travelled by ants. As soon as the ants pick up seeds, they are more likely to be large and successful than those born in crappy conditions.

Cool, but rare.

Reasons against dispersal

Especially on islands, there is a small chance to reach suitable habitat off island. Do not invest into dispersal adaptations. Why is it good to move away from parental plants. Cartoon shows this all very clearly. Dandelion parachutes depend on volume to go far or less far.

Started with mainland species, as flight apparatus is genetically controlled, some produced small parachute (low dispersability). Unimodal sized apparatus. Assumed there was some apparatus.

Bridge gap, made it onto island. Because more likely than not, large volume seeds, the overall dispersal was bigger than the one on the mainland.

Strong selective pressure limits the big dispersers, more likely to land in the water. Overtime, intermediate populations moved away from high volume, more towards medium.

Reduced seed dispersibility on islands. On hawaii.

Wind-dispersed (mainland): little wings, smallers, float.

Hawaii seeds: Larger, straight, sink.

Seed dispersal syndromes

The hypothesis for seed dispersal are the reason for seed dispersal adaptations.

Anemochory: Wind-dispersed. Hairs are feathery, common-milkweed. Wings (birches). Tiny, winged, orchid seeds. Poppy. Tumbleweeds. As it hits the ground. seeds fall off the plant.

Hydrochory: Hard seed case, airpocket to float. You can find them near tropics and the sea. Their hard coats stay intact in the abrasive sea for a long time. Common along big tropical rivers (amazon). Trees along seashores. Coco de mer (world’s largest seed) - surprisingly light and only one embryo.

• Splash seed dispersal: perfect angle of open ovary walls to harvest maximum impact of raindrop. Energy of raindrop will catapault seeds away.

• Thick shell case, air space inside, long-lived embryo, ability to float.

Myrmecochory: Forest spring flowers in ON rely heavily on this. Where ants collect seed with elaiosome. Ant pick up seed and shove back into nest. Feed to offspring. Elaiosomes only get removed from seeds inside the ant colony, fed to larvae.

Exozoochory: hooks and barbs of seeds. Catches onto clothing. Grow to animal size.

Evil exozoochory: Seeds located inside the pod, hole where ripe seeds are dispersed, sticks in things. Gets really attached to a shoe or foot. Low key dangerous.

Endozoochory: Birds have no teeth, but adapted stomachs. Grinds and digests the seeds. Gizzard stomach. Birds swallow pebbles to digest food. Thick seed coat to survive. Will not germinate until after it has migrated through gizzard. Gets scarified.

Barochory: Big, fatty seeds. Great winter food. Seeds fall from plant when ripe. Seeds are picked up by animals and dispersed. Scatter hoarding.

Stack habitat, lots of individual seeds in caches, some will be forgotten and they do their germination thing.

No seed dispersal adaptation: in many small, r-selected weeds. Mass-produce small, cheap seeds. Hopes for the best so some make it to good sites. Parents are often annuals, okay for offspring to not disperse, cuz they’ll inherit the spot.

Overview of seed dispersal

Larger classes are barochory. They trust they’ll be cached. Ant dispersed seeds are a little wider.

In 2 deciduous forests in indiana. Categorized into seeds. Stand in for Ontario forest. Overstory and understory woody species were distinguished. 38 were other.

33% of ontario plants are immigrants

Barochory - bigger seeds but no actual dispersal mechanisms.

Herb seed dispersal: Ants are the largest single animal disperser group, 60% of herbs are ant-dispersed seeds.

Seed dispersal distance

Larger fraction of seeds move further away with adaptations. With or without adaptation they land close-by, but more travel further out with adaptations.

In both cases, most seeds are deposited close-by. Wind-dispersed seeds average travel distance is generally much further than animal dispersed seeds.

Hydrochory splash seeds don’t normally travel more than 1m. Enough distance given small stature of splash-seed dispersed plants.

Ballistochorous: Falls to ground and some move less than 5 meters away. Only few are taken very far away. Lots of herbs and seeds disperse not very far.

Myrmecochorous distance: mostly less than 10 m. Very few, but some can move up to 8000 cm. Few can go up to 80m.

Exozoochorous dispersal distances: Bunch of different plants. Either had adhesive structures, or there were no adhesive structures. Average with adhesive structures was nearly 15, 3x longer dispersal with hooking mechanisms. Animal size dependent. Animals try to get rid of it when they notice.

Endozoochorous: complex and dependent on gut passage time, home range, and migration season. Migrating ducks can bring it 1000s of kilometers. Most deer go 100s of meters.

Long distance dispersal

Up until 16 000 years ago, big parts of north america was locked under ice, so all species in these sites survived in the ice age somewhere south, and had to migrate north. Depending on how they got there, they could come back or no. Average max dispersal is 30m a year. How far did american ginger travel with help from ants? 23m a year - 10 km in 16000 years. If we take measurable dispersal distances per year, they should only be 10km above the edge of that ice age - EXTREME LONG DISTANCE DISPERSAL

Abiotic or biotic vectors. Major hurricane in USA. How far human made designs were picked up and dropped out of sky (paper, light things, heavy things (chairs)). Heavy objects could move up to 80 km, and one instance of 170-180 km. deposited far away from where species survived ice age. How north america got recolonized.

Colonization of unoccupied habitats. Hard to study, too rare in frequency and difficult to track (hurricanes and major events)

Ontario has 32% alien species. We inadvertently move seeds with us. Smaller areas within the country.

Dispersal in time

Fire dispersal: seed dormancy, highly nutrient-poor soils and fire-prone habitat, serotinous cones.

Seed dormancy: suspension of the embryo. Mature seed doesn’t germinate right away (waiting for a time period). Lag time between when it is mature and starts to grow. When drought period is over, or there is more resources, or less competition

• Break dormancy: changes in light, embryo maturation, stomach acid, plant hormone, smoke

Fire-dispersal break dormancy when it becomes warm, or they sense smoke chemicals.

Habitat is so dense, it can’t find open space, and burning allows there to be room. “All” nutrients stored in living plants (soil ultra poor). No space to germinate.

Serotinous cones - Jack pine. Multiple generations of cones on branches (closed, not releasing seeds) it knows there's no nutrients and its safe. Fires are patchy, you can see all the different shits.

Jack pine on very nutrient poor soils on the canadian shield (oldest global bedrock).

Survival under low-nutrient conditions

Low-nutrient conditions

96% of plant dry matter is made up of hydrogen (6), carbon (45) and oxygen (45). Mostly in water or carbon dioxide.

It is very difficult for plants to access nitrogen and phosphorus. How do nitrogen and phosphorus become bioaccessible.

P: bedrock → weathering → soils → living organisms

• Geologic

N: atmosphere → (soil/symbiotic) bacteria → all living organisms.

• Biogenic

Phosphorus from bedrock: depending on its chemical composition, contains different levels of P (no to little to more).

Main source of phosphorus rocks

Moves through water and can be joined in water, it will infiltrate in soils, remain, and it can also exit the soil into the solutions. Eventually precipitate. Accumulate at the bottom of the lake. Year by year there is a build up. Plants can access phosphorus from soils, but that's difficult and they need helpers. Have phosphorus. All life dies. Decomposers everything and that can return phosphate in soil. Most forms of phosphorus are bio inaccessible. Not everything is taken up, so we get leaching out of biogenic back into geological cycle.

Soil phosphorus levels decrease over time. If we’re looking at soil age and quality of nutrients, it’s highest at the beginning of the first few million years. Old ancient soils are depleted.

Nitrogen cycle: obligate organisms - there is no life as we know it on earth without them (red). Facultative helpers (green).

Symbiosis on plant roots. Give part of the nitrogen to the plants. If it doesn’t go through nitrification, it can go to nitrifying bacteria and become nitrites. Without nitrogen, life wouldn’t be happening. Starting with no nitrogen soil = very nitrogen limited, you need a good amount of time for bacteria to do its job. You need tiem pretty much. Cycles through organic waste, taken up by symbiotic helpers like mycorrhizae.

Young soils have no organic material or N. poorly developed has none, then it gets a bunch, then ancient and weathered soil lose N again.

Young soils don't have a lot of nitrogen, but then nitrogen also goes down as a result of phosphorus - living without phosphorus becomes too dangerous. Less phosphorus less of everything, mainly nitrogen. Soils in Ontario are on their rise in nitrogen, but are missing out on phosphorus.

Recap of biogenic nutrient uptake and soils

Cation exchange capacity CEC of soils: Clay and humus are dead and organic matter. Negatively charged sites - surrounded by water.

Whole range of cations can bind to these sites. As long as there's water there's a push between of whether things are there or being dissolved. This part of the nutrients is especially important. Plants can only take up nutrients that are in solution. Element with highest affinity to negative sites is hydrogen. Whenever it’s there it'll be there in negative sites.

Exhaustion of the rhizosphere. Plants ‘mine out’ minerals in their immediate rhizosphere. Often plant roots/hairs are too large to get tiny soil pores, which is where mycorrhiza comes in.

Taking up cations: The carbon dioxide in the soil solution from the plant reacts with water to produce bicarbonate and a hydrogen proton. The hydrogen protons are then exchanged for cations on soil particles allowing the plant to absorb the now dissolved cations

Strategies for access to nutrients.

1 g of soil has 10¹⁰ - 10¹¹ bacteria. Up to 200 meters of fungal hyphae. Hyphae everywhere, simple for plants. Needs to make up for microbial contribution lacking.

Mycorrhiza

Introduction

Mycorrhizal fungi is a symbiont - C from living plants partners. Pay stuff back.

Mycorrhizae give nitrogen, phosphorus and water. Plants give back carbon.

Mycorrhiza is fungus and root system. Symbiotic association between plant and fungus colonizing root cortex. Plant carbon goes to fungus. Inorganic fungal minerals → plants. Mycorrhiza - huge increase in accessed soil space.

Plant - fungus: symbiotic exchange of goods. Gets limiting minerals from soils. Take up nutrients. Phosphorus is key in exchange of plant and fungus, takes up from the fungus. Has biochemical exchange rules. Phosphorus can be taken up by the plant directly. Much wider biochemical. In return, symbiotic fungi get sugar from plant. Water is much more effective through fungi and into plant body.

Certain amount of species maximized a hyphal length. With few hyphal, huge proportion of something. More fungi more they eat phosphorus, more limiting, more in plants. Happier the plants. Plant vigor biodiversity.

Well being of plants: Root biomass from very little to a lot. We can look at overall plant diversity. How many are in the game. 0 means 1 species of plant (plant diversity).

Types of mycorrhizae

Arbuscular mycorrhizae (AM, endom, vesicular-arbuscular m):

Things are happening in the hairs. Anywhere from epidermal hair to purple cortex (endodermis).

Arbuscule - trees. Where the exchange of plant and fungus happens. Cells of the cortex, some arbuscule connect. It's like the lung, where the stuff is interfacing and exchanging. Vesicles are storage organs. Interface. Arbuscule (endo) grows inside cells of the endodermis in contrast to the next type (exo)

AM fungi is an obligate symbiont → limited saprophytic ability (dependent on plant C). On average, 6% of plant’s C to AM fungus. 6x better P uptake into AM that plant root (N, H₂O). No visible fruiting bodies - subterranean spores. AM fungi really bad at working with dead material, and it totally relying on plant carbon. Gets 6x better phosphorus uptake. Comparison of tiny root hair. When you see mushroom is it not AM fungi - they are in the soil, reproduce in soil space.

Oldest and most prevelant connection, what we believed first land plants looked like. 410 million ya there were arbuscles present. AM fungi are everywhere. 80% of all species. Woody and non-woody species.

Ectomycorrhizae (EM):

10% of plant families have this. between and outside cells of the cortex.

The fungus can only grow between cells

EM fungus is located outside and inbetween the root hairs. A lot of our species have ectomycorrhizae.

Yellow cortex plant cells. Ecto can't bridge this - it spreads out space between cells, makes roots look slanted. Inbetween, there is a weird netwoork of fungi between in the lines. Ecto mycorrhiza lives in between cells. Network in between is called hartig net. We're inside the cortex. Inside cortical cells. Very few cortical cells there are. More ecto than actual cells. Equivlent of hartig nets. Whatever moves between plant cells needs to move between the hartig net

Roots of EM → Short, stumpy, rounded.

Hartig net - close interface for exchange of goods between fungus and plant (P, N, H₂O, C). Anything moving between cortical cells passes through this.

Mushrooms are EM. Back and forth between fungus and plants. Many things we eat at EM. Some are dealy though - fly agaric, death cap.

Ericoid mycorrhizae:

Growing with plant order Ericales. Common peat bog plants. Epidermis with root hairs → Only one cell layer deep. Mycorrhiza is inside. In one cell layer, it can grow inside like EM.

Cortex is only one cell layer thick, it gets into one cell layers. Ericoid fungi.

Comparative overview, ecology and evolution

AM (Endophytic) → EM (Balanced) → ErM (exploitative) (evolution) - simplified tree of life.

Large hyphae extending the area. Fungi have a big arsenal of enzymes. Having a large interface with hyphae and having enzymes is critical for getting nitrogen, phosphorus and water.

Latitudanal MR pattern: fungal biochemistry and organic matter. EM has a wide range of enzymes, used to break down plant cell material. One big difference, the occurrence of organic matter is not distributed equally worldwide. Decomposer kind of.

There are lots of biomass in areas with EM, because of the quick turnover rate of carbon. AM fungus have low biomass.

Enzymes are costly, subsidized by symbiotic C from plant partners.

Ectomycorrhizae there to break it down. Theyre good at it.

Makes them live in areas with lots of organic matter.

Arsenal of enzymes doesn't come free.

EM is the most expensive metabolism.

ErM - 3% of NPP per tree. AM - 6% of NPP per tree. EM → 13% of NPP per tree.

• NPP - Net primary productivity (stolen from host)

In bryophytes, majority have a specific mycorrhizae, otherwise the predominant is AM. Uneven distribution of mycorrhizae. We have arbuscular. What is happening inside angiosperms. We have three main groups.

Monocots - main, big group. Similar to lower vascular plants, the predominant is AM. Differ from core eudicots and rosids.

Fossilized evidence of fungi is extremely difficult to find. If we go into fossil record, the cross section of stem already has arbuscules. Evolution of plants did mycorrhizal fungi. In parallel to changes to land plant, moving towards symbiosis.

Source of photosynthetic C (in plants and leached to soil) for heterotrophic fungi: First plants developed in the water. Were very primitive. No xylem phloem, rudimentary roots, no leaves, very primitive plants. Flat liverwort as an example of early land plant. Fungi being heterotrophic, fungi leached carbon is interesting. They are attracted and growing towards these earliest of land plants.

Early land plants: some soil fungi evolved to be endophytes. Fungi attracted to leaked PS carbon → grow on plant surface. 2. Penetration of living plants by fungus without harm to plant (close to course of PS C). 3. Endophytic fungus with soil hyphae: shelter; no predation; no competition; first to feed on plant once it dies. 4. Fungal dependence on PS plants products, but fungus retains soil connection (water, minerals): setting stage for symbiosis.

Primitive stem. Stuff pushes through. Lives partially in and out of soil. Carbon living plant is almost photosynthetic. Maintaining soil hyphae. Partially sheltered from any pets. Exchange between 2 organisms. Living inside the plant. Intercept carbon (arbuscule). We see the inverted negative lungs coming in. Plant can intercept some of the chemicals.

Peak specialization of roots. Minerals from fungus to the plants. Trying to something fungi for free. It's worth mentioning arbuscules are shortlived. Arbuscules active for weeks and then they decay Plants developed arsenal to digest dead arbuscules, growth is not uncontrolled. Control what fungus is doing. Construction of fungus biochemically, evolves to become a better habitat for friendly fungi. While plant is changing its cortex, it's getting better at chemicals. Where plants and mycorrhizal fungi cannot live without plant partners.

Looking at changes in land plant. Development of root. Biochemical arsenals to digest arbuscules. Arbuscules and they become extremely specialized. First one to feed on plant when it's dead. Parasitism - fungus or plant takes from the other without reciprocation.

Balanced → parasitic: no chlorophyll, no photosynthesis. Non-green plant parasite steals PS sugar from green plants via joint mycorrhizal fungi. Symbiotic fungal root, forego photosynthesis, not green, still connected to fungal network, non photosynthetic plant.

Mycorrhizae → gets P, N, H2O. Next one gets nitrogen.

N-fixing bacteria (rhizobium)

The atmosphere is mostly inert, bio-inaccessible nitrogen. Facultative helpers get bio-accessible through bacteria.

Leguminous roots: Rhizobium can be found in nodules on these.

Three groups of prokaryotes fix N in symbiosis. Rhizobium most popular, Only in legume. Makes wonderful food. Two other important groups of bacteria. Frankia - angiosperms (not related), makes connection. Nostoc - blue green algae or cyanobacteria, synbiotically live with one genus.

Gunnera and Nostoc: cyanobacteria. Cross section of stem in a gunnera. Nostoc bacteria lives in the stem base.

Alder trees and Frankia - Alder lives close to running water, habitats tend to have nitrogen washed out. Ecosystems close by are nitrogen depleted. Alder trees symbiotic with frankia, allowing it to live in nitrogen depleted environment.

Bayberry and Frankia - Bayberry is a shrub in gravel and sand. Barberry colonizes these areas with Frankia on its tail. It becomes more and more closed. As now soils are more enriched in nitrogen.

Rhizobium

In nodules on legume roots. Living inside roots, as a bacterial nodule.

Lupin (legume) + Rhizobium - Leaving behind completely new soils. Lupens belonged to the legume family, have rhizobium, enriching soil in this area post disaster. First wave able to survive N-devoid volcanic soil.

Leghemoglobin helps to capture free oxygen which allows the process of nitrogen fixation to run

Rhizobial infection: It starts outside of cross section. Free-living rhizobium are attracted to leach carbon from root hair (they're nearby by chance). Curl and it continued to grow. Infection thread in infected root hair. Grow through hair and into the cortex. Heavily divide. Evermore. Root nodule where rhizobia bacteria start to divide. Vascular tissue, move stuff into. Infected thread curls.

Rhizobium symbiosis (with plants):

Legume proteins: healthy planet. N to plant, and then the Rhizobium incorporated into seeds. Good plant protein on your plate.

Same type of trees. Gunnera seed.

Paper analyzing 3 groups - in the evolution to plants and ancestors, one gave rise to all families, only one predisposition. Single. Multiple evolution of symbiosis (frankia) and one with rhizobium.

Rhizobium infection: has infection thread, and a developing root nodule stuck in cortex. The nodules contain bacteroides.

Over evolutionary times, nodules have become the perfect ‘housing’ for legumes. Rhizobia produce leghemoglobin which captures oxygen, because nitrogenase produced by rhizobia, only works in oxygen-free environment. Nitrogenase is the enzyme that catalyzes the reaction in which inert atmospheric nitrogen gas is turned into bio-available nitrogen. This reaction is expensive and powered  by the plant .

Cluster roots

Cluster roots are steroids. Huge clusters. Occur like beads on a string. Way more carbon building blocks. Minerals and phosphorus. Very common in old soils.

Different types of cluster roots: Simple (more root and root hairs). Complex (Branched system). Complex have a huge surface area (25-33x higher volume than normal roots).

P extraction from organic layer: Bed rock may or may not contain phosphorus. Major parts where roots grow is essentially depleted. When vegetation dies, the material is decomposed. Phosphorus is released on recycled from standing vegetation. Plants typically insert cluster roots. To get access - plant has very deep root system. High concentration at high concentration.

There is a narrow window for phosphorus availability. Upper most soil. Plants taste competition of the soil. Spike of phosphorus. Epidermis cells begin to grow clusters. Most available between acidic and alkaline soils (7 pH)

Reactivity of soils. Acidic and alkaline soils. Higher absorptions, less likely to access. Low levels good. 3 curves show what typical chemicals interact or precipitate. Interacts or absorbs iron.

Down towards balanced soil. Phosphorus starts reacting with calcium. Wide window where phosphorus reaches low absorption (most likely to be in solution). Small window of availability.

Old soils are P impoverished, in southernmost tip of Africa. Requires lots of tools.

Sprout epidermal hairs. Life of cluster roots. Sprouting hairs. Around day 7-8, they turn brown where roots start senescing (aging). Cluster roots are expensive and short lived. Work hard to get last bit amount of phosphorus.

Senescence: long lived cluster roots.

Cluster roots release carboxylates to surround roots to displace inorganic phosphorus from soil particles.

Over 50% of the carbon produced by plants is used to grow, maintain, and biochemically run cluster roots.

What cluster roots do biochemically to grab the phosphorus. Plants release hydrogen protons. Produce ATP and break ADP. Hydrogen grabbed and inside and outside the

More hydrogen protons more acidic. Pumping hydrogen is not for free.

Carboxylates are used to liberate more phosphorus. Liberate inorganic phosphorus. Grabbed biochemically by the root.

Enzymes pumping outside, help grab phosphorus, taken up by phosphorus specific channels. Produce expensive phenolics. Like a low level toxin. Microbes need phosphorus, decreasing their growth means plants are more likely to get phosphorus. These reactions are very high level biochemical adaptations. Cluster roots do them at a very high level. Roots acidify around roots.

Cluster roots are typically in slightly alkaline soils. Cluster roots decrease soil pH.

Triple cost of cluster roots. Morphology (growth), physiology (maintenance, respiration), production (exudated biochemicals). Over 50% of all C produced in PS needed for P uptake.

Clusters made up of 3 units

• Need carbon blocks. Roots need to run. Respire to keep them functional. All need to be reproduced. Does not come free. Carbon cost of clusters, unit time. In days 0 to 21. time by which cluster roots are dead and no longer functional.

• As soon as cost of roots take shape, they start working. Some restoration and carbon is used to produce all chemicals that need to be dealt with (exudation). Around day 12, stuff is at peak functionality.

• More than half of carbon fixed in leaves, goes towards the function of picking up phosphorus.

Distribution of cluster roots among angiosperms: Same system of branches of angiosperm tree of life. Several families in one group, which are able to grow the cluster roots. Very same group in which families are able to produce cluster roots. Need to grow cluster roots. Evolution was independently in multiple families.

Goes down very little. On top of this, various ways plants get limiting nutrients.

Move to older - ericoid mycorrhizae, while younger have EM and AM.

Crappy soil, no long engage in mycorrizal stuff. Grow simple clusters.

Best way to get at limiting resources.

Carnivory

Changed leaf morphology to go after N. Carnivorous plants, young leaf does photosynthesis, it will grow to ever increasing size, until functional. Pointy end of leaf. Traps are mostly after nitrogen.

Pitfall traps: Lid → insects crawls in → gets stuck in water or something at the bottom → lid close. Passive. Container with digestive juices. Transparent windows. Slippery rim, teeth, hairs, lid. Has digestive juices. Genera over time broke down, building blocks taken up.

• Transparent bright spots: backside of opening has no chlorophyll. Appears as lights, insects like that and fly inside. Crawl toward their death

• Slippery rim, teeth: grooves pointing towards the center, backward facing teeth.

• Backward pointing hairs: When insects are inside, traps make it easy to crawl one way, but not the other. Hairs can be huge, intermediate, or small. All pointing downwards.

• Lid: stop water from coming in, lowering concentration of enzyme that decomposes the insects.

• Tree shrews poops inside some that have tasty leaves. It’ll lick glands with nectar. As it sits, it shits. Plants get access to limiting minerals.

Flypaper traps: surface area of leaves have nectar looking glue. Droplets or whatever else are stick, and flies get stuck. Active. Sense environment when prey is near. Sundew: Sticky glands, look like nectar. Glands will grow to fly. Big exposure. Structure roles, additionally traps the insects. Leaves turning in, squeezing. Digest it.

Snap traps: venus fly trap. Closes when it feels the movement. Both sides have 3 trigger hairs each. Insect lands, nectar involved. If they touch trigger hairs twice in 30 seconds, it’s not just wind and the trap closes. As moving inside, trap closes more and more.

Suction traps: bladderwort is a plant that is helped to float. Structures, actual traps, catching zooplankton. Microscopic traps. Tiny suction plants where three hairs when touched, will release trap.

Small glands outside are triggered. Starts closing till both sides almost touch. Fastest known underwater trap. Smallest movement can trigger invagination. Once water is in the bladder, it dies. Trigger hairs, elasticity, shot inside.

Typical habitats of carnivorous plants are nutrient poor, with lots of sun and water.

Different trap types, what the structures and species are. What is taken out. How important are the dead animals for the nitrogen budget.

Some species cover almost 90% of nitrogen through catching animals. 10-90% typically.

Drosera pallida - 13% from roots, and the rest from traps.

Cost of traps: only use it when necessary. How plants do the math? Sticky enzyme is expensive. Stickiness in newtons. Plants grown in different place. Grows in sun, nitrogen is not limited. Can only grow more carbon building blocks. What are plants actually doing the math of.

Sun low N, it is motivated to grow the traps. When limted by sun, it cannot afford to be sticky. Not motivated to be sticky when N is high. Plants are able to do the math.

Parasitism

Facultative parasitism - it can live without host, but it does better with host.

Obligate parasitism - it cannot live without host, it must be attached to host

Hemiparasitism: is photosynthetic, only taking water or soil nutrients. Has chlorophyll.

Holoparasitism: No longer photosynthetic, and it is starting to take sugar, as well as water and soil nutrients. No chlorophyll.

Root parasitism

Establish connection with host via the root. Smallest class of parasite - internal parasitism - inside roots. May see only slightly above ground. Beach drops.

Shoot parasitism

Mistletoe: Hemiparasite, still green. Seeds are sticky, glue to branch. Tend to roost in trees. Can have multiple mistletoe species on them.

Dodder: Holoparasite. No connection to root. Grow on trees. Giant mess of spaghetti. Daughter outcompeting on light access. Double on the one hand. Losing access to light.

Internal parasitism

Raffesia, root parasite. Produce soccer ball sized buds. World’s largest flower. Mostly spends time in the roots itself.

***

Evolution: Autotrophic free-living → hemiparasite facultative → hemiparasite obligate → holoparasite obligate

Haustorium: organ of parasitic plant. Attachment to host. Parasitic root, forming physiological bridge between host and parasite.

Hemiparasitism: lateral haustorium. Haustorium in hemiparasites (faculative). Started to grow next to a compatible host. Functional. Root system will branch. One random branch of the network parasite. Produce haustorium, produce structure of the host. Grown out of side roots. Primary radical, out of side roots. Horizontal haustorium: Root of a hemiparasite. Out of the root, the hemiparasite grows haustorium. Establish a xylem to xylem connection to the parasite. Hemiparasite needs to know something to steal the goodies.

Holoparasitism: Terminal haustorium: radical from primary root. Has to establish connection very start. Limited resources. Makes connection by starting to steal. Establish xylem to xylem, phloem to phloem.

How holoparasitic dodder establishes connection with the host. Stem of the host, host tissues. What the host of the herbaceous whatever look through:

Close up of vascular bundle. Water conducting tissue. Outside is the phloem (sugar conducting). Phloem and xylem - dodder needs to connect to.

Another way of looking at connection - parasite hasn't connected all the way, but tissue has been able to grow between cortex of the host.

Parasitic xylem to host phloem, host xylem to parasitic phloem: Parasitic xylem, as phloem has connected. Parasite needs to know which tissues to connect to which tissues.

Establishment of haustorium

Finding (correct) host

• Host’s root exudates.

• Especially important in a holoparasite. Needs a radical. Sense environment, senses carbon characteristics. Exudates as root is doing it's thing.

• Right host based on ligen carbon. Grows towards the host.

  Life cycle of a facultative.

Attachment to host

• Stimuli for development of haustoria

• Started germinating. Seeds just start germinating when things are good. Starts growing. Only if it senses, established facultative it will start producing the haustorium.

• Need to sense occurrence - haustorium inducing factors, adding/increasing vegetative growth to parasite.

• Seeds will only germinate if they can sense host root is close by.

• Connection will happen, parasite will increase the vigor of growth.

  Side roots sense a further presence. Lateral haustoria was produced. As parasite continues growing.

• 

• Race against a depletion of seed resources. Connect before water and reserves run out.

Penetration toward host conductive tissues

Establishment of connection to host tissues

***

Parasites do effect host. Real cost to the host. After the parasitism has been established. Logarithmic scale. From 4 to 16 weeks. 3 ways to look at it. Able to grow without a parasite. Parasite species one and parasite species 2. grows to max amount per individual. Decrease in host shoot mass.

Presence of parasite number one brings it down to 50%, only 45% of it's possible size. Looking in a picture, there is a compatible host.  Presence of parasite results in bleaching, part of the above ground leaf area of the host.

Striga suck it's nutrients. By the time you see striga emerge, the crop is emerging, and it's too late.

Trap crops - send out signals to seeds. Don't allow striga seeds to germinate.

Host defends effectively and stops striga seeds and they die. They're good in the fight against striga.

If a field is being overtaken. Abandon for a year, grow the trap crops instead, and then come back. After one or two years of trap hosts, farmers can go back to mill it. All seeds of striga are gone.

Parasite and host often compete for light in hemiparasites connected at the root. Hemiparasites do increase biodiversity in grasslands. More overall diversity.

all are polyphyletic. N and cluster are in a few different of their own clades.

Survival in hot deserts

Water limitation is dealt with in a few different ways

Problems association with desiccation in plants: Damage to photosynthetic apparatus, biochemical damage to cellular macromolecules, accumulation in UV-induced damage, irreparable disintegration of membranes.

Resistance → tolerance or avoidance

Escape

Tolerance

Desiccation tolerance. Desiccation tolerance is uncommon in angiosperms (they can’t survive losing all their water), all have been able to avoid complete loss of seeds. Mouses are the champions of surviving all water loss. Tissues resume photosynthesis and they can survive. Real issue, is most groups, except for mosses. Mosses can’t dehydrate.

Problems with desiccation: Mechanical damage due to shrinkage. Disintegration of membranes. Aggregation of macromolecules while shrinking. Disintegration of PS apparatus. Accumulation of UV-induced damage while dry.

Prime solution: Sugars (trelahose) takes place of water molecules. No aggregation of macromolecules and no disintegration of membranes as cells dry. Stabilization of drying cells. Mostly trehalose taking place of water molecules. Any structures propped up by water, were propped up by trehalose. One protein, another protein. Proteins are set apart by water molecules. Plants will stick on trehalose, occupying the same space as the cell.

• UV damage is dealt with in another way → As it is undergoing desiccation. Underside of leaf has hairs. Shields most sensitive of tissues (PS tissue). Curling up. Chihuahuan desert. South African angiosperm. Roots don’t ancho it to the soil. Over period of time, plant expands with moisture. After 7 days can PS again - reverse that.

Avoidance

Drought-deciduous perennials: During wet times, plant has leaves. As it is exposed to high heat and low water. It can’t keep up and drops all leaves. Hibernation, adult structure abover ground. Comes back to PS life when enough water again.Leaves can’t retain H₂O. Drop them, regrow them after the next train.

Leaves being dropped are continuous, not all or none. Under dry conditions, leaves are dropped. Fully drought deciduous species.

Ocotillo: Once water is going, it’ll toss the leaves, maintain water in roots and stems. Stomata in leaves, so without them, they can’t lose water really. In flower, dropped leaves. Drop and regrow on multiple occasions through the year.

Evergreens: Under dry conditions, maintain green life and some level of photosynthesis. Evergreens keep some proportion of leaves. Keep at least some leaves year round.

There remains some level of photosynthetic activity all year round (active). A year from fall to spring. Max proportion of leaves. Lateral stem leaves peak in March-April, while the main stem leaves August and March.

It’s a relative productivity, the hot period. Active productivity happens more during cold months, and continues into May.

Evergreen desert plant typically have stomata located in pits/crypts which are covered in trichomes

Sclerophylly

A major evergreen adaptation to keep it going

High leaf toughness. Glass leaves, very strong leaves. Takes a lot of force to punch a hole into them. Tough, long-lived. Adapted to arid climates. Stronger than flimsy, short-lived leaves, and temperate climate.

There are lots of sclerenchyma, making it tough. Dead at maturity, cell interior almost completely filled. Cell walls thickened with cellulose and usually strengthened with lignin. Function is structural strength. Expensive to produce. Organelles have been squashed by the growth of cell walls. Sclereids (round) and fibers (long)

Desert plants insert sclerenchyma where it is smart to do so. The more there is, the tougher. Fewer cells that actually do photosynthesis. Green patches are cells that do photosynthesis.

Smaller and or dissected leaves. Ability to fold and unfold. Besides being tough, they’re small and dissected and tiny. Leaves can stay cooler. Pine needles. Why small/dissected leaves - leaf dissection size correlates to boundary layer, correlates to dissipation of heat. Leaf temperature goes down with leaf temperature.

Nature of boundary layer - decides dissipation of heat

• The sliver of air surrounding all of us, where there is a gradient between body temp and surrounding temperature. Happening in leaf and distant air.

Wind velocity in free stream - uninfluenced by anything else. Slower the wind motion is when completely close to the leaf. Little greenhouse.

Thickness of boundary layer is function of leaf size and dissection. Further away from leaf → more heat stuck near and in leaf (less dissipation). Closer to leaf, smaller boundary layer, ridges and small leaf → less heat stuck near and in leaf (more dissipation).

Decrease leaf temperature, protect PS apparatus, save H₂O.

Dry leaves are folded. Wet leaves are open. Aided by hinges. Hinge cells with low H₂O is flaccid, slim, with lots, it’s pumped up.

Same grass under conditions. Hinge cells are inflated at maximum, induce complete opening of the leaf. PS islands get exposed to sun in wet state.

Thick cuticle. Decreased water loss. Sclerophyll does their darndest to hold it together.

Stomata in crypts. Sclerophyllous leaves often have stomata in crypts. Surface of leaf exposed to cuticle. Crypts - areas where stomata are located. In normal plants, they’re in the underside, but here they’re in crypts. Having stomata exposed less to wind, slows down the water loss.

Leaves often with trichomes. Trichomes inserted in crypts. Inserted outside, slowing down the wind, decreasing the water loss.

Very dry to wet. One plant along precipitation gradient. Very dry vs. moisture. What proportion of the leaf has hair. Abundance of hair follows clear precipitation gradient. Proportion without hairs is chill. Hairs inserted more sparsely, more green. Allows leaves to be cooler.

Hairs cool down leaf. Green leaf has significant hotter leaf temperature. Significantly takes care of PS apparatus in leafs. More hair, less light reaches photosynthetic tissue. Desert plants know when to grow hairs. They do the math.

Adaptive exposure to the sun

Adaptive exposure to sun - depending on exposure of lead to light reflected. Desert evergreen has vertical/cylindrical orientation, and are small. Can track sun.

Water stress - leaf cupping lowers leaf area. Max exposure is in the early morning or later afternoon. When it is the hottest, stuff keeps cool, when it is cooler they’re ready to go.

Leaflessness, green stems

PS productivity with enough water: leaves > stems, but leaves lose more water than stem (thicker cuticle, more stomata). Under high stress, they toss leaves.

Leaves > shoots > twigs. Effectiveness of photosynthesis by leaves. Just green twigs. Little light, to lots of light. Leaves better than shoots, twigs worst. Throw in water conductance - how much water moves through the twigs, leaves have much more water moving through them. High loss of water = more carbon per water. Adaptive to maintain green stems for this.

How much photosynthesis is done vs. month. Lots of variation (we don’t need to know what the groups are). How different stems affect photosynthesis. More or less reliance on using stems as photosynthesis.

Adapted roots

You don’t just get deeper roots to reach water bed. Surface water and drainage play a role.

Soil H₂O profile (rain, drainage)

Plants in the upland can not reach the water table, so they have to use rain. Impossible to grow long enough roots.

Dry gap. Water and water table doesn’t reach through. Plants can’t afford to get that far down, so they maximize surface roots when it rains.

Heavy rain washed away top part of soil. Really dependent on shallow roots before it evaporates. Excavated root system of a shrub. Clearly dimorphic roots, trying to harvest as much as possible. Surface rain. Evergreen shrub.

Dimorphic roots: hydraulic redistribution of H₂O. Two root systems have a really important interplay. Trying to expand life cycle of the short-lived roots.

Under drought (night), the plant can access water from roots. Filling up with superficial roots. Take water from shallow superficial roots.

Once it's rained, superficial roots supplements extra water into the deeper roots

Passively pumped - extends life expectation of short lived roots. They might die with a lot of drought, but keeping water down doesn't do much change.

Paper uses complicated way to show range of depth. Focusing on average. If you are a big plant, you grow deepest roots. Succulents have the shallowest of all roots. How wide do roots spread. Trees have widest, then dramatic sink, but succulents have relatively large. Extended system.

Trees grow deepest. How well can they match depth of ground water. 1:1 any tree with roots match line, they can grow exactly as deep as needed to perfectly reach ground water. Most species do not grow their roots very deep, but some can go to 70m.

The deepest rooting depth has been recorded to be 58m and is that of a tree . Succulents tend to be the least deep rooted species. In terms of lateral root spread, Trees have the widest and Annuals have the narrowest.

Salt resistance

Species able to survive salty soils. Poses a problem for species that grow at the valley. Rare rain, hits mountain, washes out salt into valley, infiltrates sediment. Can see whiteness of pan and valley bottom.

Absorb water from soils with very low water potential, maintain even lower root water potential. Overcome salt toxicity.

Salt accumulators

Stash salt away in subcellular organelles. Doing what normal cells are doing. Streaming in from inside, stuff in vacuoles, accumulators are succulent.

Partial pressure of vacuole. As salt ions are coming in, move into vaccuoles away from cytosol, out of harms way. Needs to manipulate concentration of cells.

 Non-toxic protein for salt. Betaine and proline not toxic, doesn't get involved with what's toxic. Chemical staining salt.

Salicornia - salt accumulator. It’s edible, tastes very salty.

Salt excretors

Pseudo salt excretors: salt accumulates in salt bladders on leaf surface in balloon-shaped trichomes. Secrete salt away, into vaccuoles. Quinoa is a halophyte. Good to grow on poor soils. Surface of lead. Epidermal cells have bladders, takes up salt, stores in salt bladders so rest of plant has less salt concentration. Gets it away, doesn’t get rid of it.

True salt excretors: Specialized salt glands secrete excess salt. Specialized glands, to more manageable concentration.

Halophytes are very salt tolerant.

Salt concentration from very salty to not salty at all.

Lupin can't take low concentrations of salt, max 100% with no salt. Barley can deal with some level of salt. Salt bush is a real halophyte, can deal with a ton.