Lecture 16: Plant Ecophysiology + Part 5 reading

What are autotrophs? What makes a plant an autotroph?

an autotroph is an organism that make its own food

plants are autotrophs because they make their own food via photosynthesis

What does photosynthesis require? What do plants require to grow?

requires:
- CO2
- water
- light energy
- reasonable temperature

- soil nutrients (nitrogen, phosphorus, potassium, NPK)

What do leaf, stem, and root traits reflect? What is an example? Hint: hot environment plants

they reflect adaptation to their environments

What are angiosperms?

plants that have both male and female reproductive germinates

What is the difference of anthers and stigma?

anthers (male) bear pollen
stigma (female) receives pollen

What is the process of germination in angiosperms?

the pollen grain from the anthers germinates the pollen tube units it fertilizes and releases sperm which then fertilizes ovules

What are flowers a good example of?

they are a good example of biotic environments

What is physiological ecology different for plants compared to animals?

- plants are sessile; they can't move themselves
- plants tolerate unfavourable conditions; animals escape them

What is the reaction of photosynthesis? Fwd and rev.

photosynthesis and cellular respiration (app energy)
- co2 + h2o using light energy to make glucose and o2

Where do plants bring elements for photosynthesis?

in functioning photosynthetic tissues

What is carbon balance?

plants must require more carbon through photosynthesis than they lose through respiration

carbon balance: more co2 reacted then produced

What is NPP stand for? What is the equation for it?

- net primary productivity

NPP= carbon gained via photosynthesis - carbon lost via respiration

When does Earth have high NPP? When does it have low NPP? Where?

- in summer months in Northern Hemisphere: high NPP (bc of more plants growing in the summer)
- in winter months: low NPP (less plants)

In tropical forests NPP is always high. Explain why?

because there are always plants growing because conditions there are optimal in those environments
- warm and wet
- favours plant growth

Where does photosynthesis occur in a plant? How does it occur?

occurs in the stems and leaves of a plant

plants take in co2 through the STOMATA

What does it mean when a plant transpires? When does it occur and why?

means that plants lose water through their stomata
(evaporation of water)

occurs during the passage of co2 and o2

What affects photosynthetic structures embodying adaptation to environmental stresses? What are the benefits to large ratios?

- leaf size and shape

benefits: more area for photosynthesis
- harvesting co2 and light

costs: overheating, water loss by transpiration

How do plants cope with overheating and water loss? What is an important enzyme and what does it do in certain temperature conditions?

- C3 photosynthesis
- rubisco; enzyme that accepts Co2
- at high temps; rubisco captures o2 instead of co2

What is photorespiration?

when plants take in o2 instead co2

How have some plants evolved from C3 photosynthesis? 2 different adaptations; what are they?

C4 photosynthesis:
- PEP carboxylase accepts Co2
- reduces photorespiration

CAM photosynthesis:
- close stomata during the day to reduce water loss
- open stomata at night to let in co2
- store co2 until the day

What are both the adaptions of C3 photosynthesis a result of?

C4 and CAM are a result of adaptations to high temperature environments

How to plants with large leaves combat overheating?

- growing in shady habitats
- evaporative cooling by opening stomata

How does evaporative cooling work in plant stomata cells?

- water transpired through the stomata cool the surface

How do plants with large leaves combat water loss? What are the repercussions of doing this act? Where are these consequences more seen?

by closing the stomata:

- shuts off all gas exchange
- photosynthesis shuts down
- plant stops growing
- risks overheating
- tissue damage

- in desert plants

What do the repercussions of closing the stomata to combat water loss mean in terms of their relationship?

there is a tradeoff between water conservation and rapid growth

Why does a desert plant live in the desert?

- desert hasn't killed it yet

What is an adaptation of Palo Verde plants? Why did this adaption occur? How do these plants perform photosynthesis? What can these adaptions also be the cause from?

adaptation: having small leaves
why: because temps were too high

through their branches and bark

drought and freezing temperatures

What do Palo Verde trees don't have and how does it help them?

they don't have large leaf surfaces that will be exposed to het stress and water loss in deserts

What is the difference between leaves in the tropics and the leaves in deserts?

deserts: small leaves; hot and dry

tropics: large leaves; warm and wet

What does microphylly mean?

means "tiny" "leaves"

What occurred in Santa Rita prickly pear plants? Where does photosynthesis occur and not occur and why? When is heat stress greatest and lowest? What did they evolve to do?

- loss of leaves
- leaves evolved into spines that don't preform photosynthesis
- pricks are defensive functions

- stems are angles towards the sun
- greatest heat load & water stress in midday
- evolved to perform photosynthesis at night

What is a feature of cacti roots?
Why?

- extensive (long) but shallow (short in how far it goes down)
- collect water from the surface of soil when it rains

How did the Saguaro cactus in the Sonoran desert adapt to episodic rains? What type of photosynthesis occurs? HINT: episodic patterns

- CAM photosynthesis
- can absorb a lot of water and use it for gradual growth and water storage
- they capture rain and it causes their accordion pleases to expand and the trunk to fill with water

Why do tropical trees have extensive and shallow roots?

- an adaptation to get scarce nutrients

NOT due to water stress since they get plenty of water compared to the reasoning behind why desert plants of shallow roots

What is root foraging?

- foraging means behaviour
- moving location to find more food

What is the split root experiment? What did they notice? What do legumes search for? What does this bacteria do? Where does it perform?

- split roots and put one in low nitrogen and the other in high nitrogen concentration

- legumes engaged in symbiosis w bacteria rhizobia fix atmospheric nitrogen
- takes N2 from the air and converts it into a form that plants can use for plant growth

- preforms in nodules on the roots

What do these graphs show us? What does it mean when there are a greater amount of root nodules?

- there is more root biomes in high nitrogen soil than low
- there are more nodules that are effective in good nitrogen bacteria then in ineffective bad bacteria

- roots are growing and forming more structure to associate with symbiosis where there is good nitrogen available

How do plants evade stress?

deciduous habits

What are deciduous habits? What are some examples?

- dropping leaves during high/low temp seasons to reduce water stress and tissue damage
- to conserve water

What does leaf shape influence? What are the two different leaf shapes?

- influences gas exchange
- laminar and turbulent air flow over leaf surfaces

Which of the two leaf shapes are better: laminar or turbulent? Why?

laminar: boundary layer that is make of stagnant air is bad for gas exchange

turbulent:
- caused by edges, pointy things, ridges, corners
- encourages gas exchange
- good for evaporative cooling
- causes CO2 to come into air near leaf surface and water vapour to escape boundary layer and into atmosphere

What is morphological plasticity in leaves? Hint: compare two leaves from the same tree
Hint: seen in Monstera delicisosa plants

shade leaf: bottom, laminar flow, less cooling

sun leaf: top, turbulent flow, more cooling

- more holes in sun leaf than shade leaf; cause turbulent airflow

What is recursive digression? How does it effect cooling?

- convective cooling is aided by turbulence
- laminar flow to reduce cooling
turbulent flow to evaporate cooling

What is convergent evolution?

- plants look similar or have similar functions but they are not closely related
- due to being in the same environment

What are epiphytes?

- plants that grow on other plants
- not rooted to the ground

What are consequences of being an epiphyte plant?

- roots are not in the soil
- leads to water loss
- leads to nutrient shortages

What is a vermilio tank? What type of plants are they seen in?

- leaves arrange in rose to let water in middle that can hole the water
- uses lots of water for growth
- uses debris that accumulates in the tank for nutrients