D+E Unit 2 Exam - Chapters 38 (Classifying Angiosperms) + 35 (Vascular plant structure, growth, and development)

Monocots

• seeds cont. one cotyledon (embryonic leaf/1st leaf that emerges)

• leaf venation usually parallel

• stems - vascular tissue usually scattered

• roots - usually fibrous, no main root

• pollen grain - w/ 1 opening

• less common as angiosperms

• have floral parts/organs in threes (or multiples of threes)

ex. incl. grasses, orchids, irises, onions, lilies, palms, and CORN

eudicots (or just dicots)

• two cotyledons

• leaves - usually net like

• stems - vascular tissue usually arranged in a ring

• roots - taproot (main root) usually present

• pollen grain - w/ 3 openings

• more common as angiosperms

• floral parts in fours or fives

ex. roses, mustard, cacti, blueberries, sunflowers

as seeds mature…

they dehydrate

water content drops 5-15% of its weight — embryo enters dormancy and metabolism almost completely stops

monocot seed (draw and diagram)

(corn)

epicotyl - embryonic shoot above the cotyledon (dev. into stem and leaves, grows upward)

hypocotyl - (region of the embryo below the cotyledon and above the radicle in the middle, connects shoot system to root)

radicle - embryonic root, dev. into primary root system

coleorhiza - protective sheath that covers the radicle (protects young root as it grows through soil)

coleoptile - protective shoot that covers the shoot

scutellum - single cotyledon (seed leaf) of monocots, absorbs nutrients from endosperm

pericarp - outer covering of the seeds (in many monocots the pericarp is fused with the seed coat)

Dicot seed (draw and diagram with part labels)

(bean)

2 cotyledon

epicotyl - grows into shoot

hypocotyl - connects the two (middle)

radicle - grows into root

simple fruit

dev. from a single carpel (or several fused carpel) of one flower (ex. pea, peanut, lemon)

aggregate fruit

an aggregate fruit dev. from many separate carpels of one flower (ex. raspberry, blackberry, strawberry)

multiple fruit

a mult. fruit dev. from many carpels of the many flowers that form an inflorescence (ex. fig/pineapple) - each segment of the fruit dev. from the carpel of one flower

accessory fruit

an accessory fruit dev. lrgly. from tissues other than the ovary—in apples, ovary is embedded in a fleshy receptacle

angiosperms reproduce sexually, asexually, or both and this means

sexual reproduction = results in offspring genetically different from their parents (genetic variation) —> meaning evolutionary adaptations are made possible

• only a fraction of seedlings survive

• some flowers can self fertilize (ensuring every ovule will develop into a seed)

• many species have dev. mech. to prevent “selfing”

dioecious

means to prevent self fertilization

species have staminate and carpellate flowers on diff. plants (so need both male and female plants to be near each other to fertilize)

stamens and carpels maturing at different times

arranged in such a way to prevent selfing

self incompatibility

most common means to prevent self fertilization

plants ability to reject its own pollen (still being studied)

• some plants reject pollen that has an s gene (self incompatibility gene in plants) matching an allele in stigma cells (top part of the pistil of a flower where pollen lands)

• recognition of self pollen triggers a signal transduction pathway leading to a block in growth of a pollen tube

asexual reproduction - vegetative reproduction

results in a clone of genetically identical organism (can be beneficial to a successful plant in a stable environment)

• cloned plants are vulnerable to extinction from environmental change

totipotency

an ability of a cell to divide and asexually regenerate a clone

how do plants know when to break dormancy

cues from the environment

desert plants —> substantial rainfall

fire prone areas —> heat or smoke

harsh winters —> extended cold exposure

tiny seeds —> light

seed coats susceptible/needing acidity —> pass through animal digestive tract (ex. Kori Luwak coffee pooped out by monkeys)

dormancy length

days to decades (most seeds are 1-2 years old, seasonal)

• oldest carbon dated seed grown (2000 y/o isralei palm)

what happens when conditions are right

• imbition (means taking in water), leads to germination

• seed expands bc/ of imbition —> this ruptures the seed coat

• embryonic root (radicle) goes down, shoot (hypocotyl) goes up

triggers changes that allow embryo to resume growth - enzymes digest endosperm/cotyledons and send these nutrients to growing areas

plants all have

cell tissues, organs, organ systems

organs are

roots, stems, leaves

organ systems

shoot and root systems

roots

are multicellular organs that anchor plant, absorb nutrients, and STORES organic nutrients

taproot system

consists of one main vertical root

lateral roots

branch roots (increase surface area for absorbing minerals and water) and anchor plant

adventitious/fibrous roots

arise from stems or leaves (instead of coming off of original root)

seedless vadcular plants and monocots all have…

a FIBROUS root system

• characterized by thin lateral roots w/ no main root

absorption of water and minerals

happens near root hairs (which inc. surface area for absorption)

• imp. symbiotic interactions w/ soil fungi called mycorrhizal associations

prop roots

legs of a tripod, but more than 3) giving exterior support

storage roots

store nutrients (starch) helps plant survive

aerial roots

“strangling” (grow aboveground, anchor plants + take nutrients aboveground)

butress roots

wide plank-like roots aboveground, base of tropical trees (structural stability in nutrient poor soil)

stems

organs consisting of an alternating system of nodes (the point at which leaves are attached)

internodes

stem segments between nodes

apical bud/terminal bud

located near shoot tip and causes elongation of a young shoot

auxiliary bud

structure that has pot. to form lateral shoot or branch

tubers

type of modified stem - (potatoes) = enlarged ends of rhizomes/stolons spec. for storing food

• “eyes” of potatoes are clusters of auxiliary buds

rhizomes

(ex. base of iris) horizontal shoot growing just below the surface (vert. shoots emerge from auxiliary buds on rhizome)

stolon

ex. strawb plant

“runners” horizontal shoots grow along surface

• reproduce asexually

leaves

main photosynthetic organism

consists of flattened blade (main surface of the leaf) and a stalk called the petiole (which joins the leaf to a node of the stem “leaf stalk”)

what do monocots lack?

petiole

this is because the base of the leaf wraps around the stem forming a sheath in monocots

simple leaf

single, undivided blade

compound leaf

blade consists of mult. leaflets - no aux. bud at its base, sometimes futher develops into smaller leaflets

tendrils

type of modified leaf (seen a lot in pea plants)

used to cling after lassoing a support tendril forms a coil that brings the plant closer to support (typically these are modified leaves but can be modified stems)

spines

type of modified leaves (seen in cacti)

actually the ‘leaves’, photosynthesis carried out by the fleshy green part

storage leaves

ex. bulb (cut onion) - short underground stem and modified leaves that store food

reproductive leaves

succulents

produce adventitious plantlets which fall off the leaf and take root in the soil

3 kinds of plant tissue

dermal, vascular, ground tissue

each plant organism has all 3 and each of these 3 categories forms a tissue system

the 3 are sort of arranged in rings, arrangement differs in diff. parts of the plant

dermal tissue

outside

• stomata = allow CO₂ exchange between air and photosynthetic cells in a leaf

• 2 guard cells - regulate opening and closing

• root hairs

• trichomes (hair-like/peach-fuzz outgrowths of the epidermis) offering protection, reduce water loss, reflect sunlight, secreting substances (like oils or toxins)

• epidermal tissue of leaf and stem produce the cuticle

• periderm = woody plants (forms outer bark of stems and roots)

vascular

inside

system carries out long-distance transport of materials between roots and shoots (wherever plant needs it)

• icl. xylem, phloem, stele, vascular cylinder, tracheids, vessels, sieve tube elements, sieve plates

stele

vasc. tissue (cylinder) inside a stem or root that cont. tissues that transport water and nutrients

vascular cylinder

in most monocots, vasc. tissue of roots is in a ring

• stele of stems and leaves is divided into vascular bundles, strands of xylem and phloem

tracheids and vessels

water conducting cells of xylem

tracheids = found in xylem of all vascular plants

vessels = vessel elements align end to end to form long micropipes (most angiosperms, few gymnosperms)

xylem

conveys water and dissolved minerals upwards from roots —> shoots

bigger tubes

think: X marks the spot (in dicots)

phloem

transports organic nutrients from where they’re made to where they’re needed

smaller tubes surrounding tissue

think: phloem phills in

sieve-tube elements

alive at functional maturity, lack organelles - specialized cells in the phloem that transport sugars and other org. nutrients through a plant

sieve plates

porous end walls that allow fluid to flow between cells along the sieve tube -each sieve tube element has a companion cell who’s ribosomes and nucleus serve both cells (sieve tube elements lack one and can’t do a lot so companion cells help them)

ground tissue

leftover cells, neither dermal nor vascular (ground tissue system)

ground tissue is mesophyll cells (palisade + spongy)

incl. cells spec, for storage, photosynthesis, and support

pith

ground tissue internal to the vascular tissue (soft, central tissue found in the middle of many plant stems (and sometimes roots)

cortex

ground tissue external to vascular tissue

layer of tissue between the epidermis and the vascular tissue

3 types of ground tissue

parenchyma, collenchyma, sclerenchyma

parenchyma

• thin and flexible primary walls

• lack secondary walls

• are the least specialized

• performs most metabolic function

collenchyma

grouped in strands and help support young parts of the plant shoot

• thicker and uneven cell walls

• lack secondary walls

• cells provide flexible support w/o restraining growth (bend w/o breaking)

ex. cellery or sunflower // petiole “strings”

sclerenchyma

extremely THICK cell walls, lignified, non-living cells that provide strength, support, structure, heft

2 types:

fibers - long and slender grouped into strands (like a twizzler)

sclerids - irregular shaped cells ex.) grit of pears or cherry stone (provide structural support to prevent imploding)

root cap + 3 zones of cells (growth)

covers root tip, which protects apical meristem as root pushes through soil. growth occurs just behind root tip in 3 zones of cells:

1. zone of cell division - cells dividing by mitosis

2. zone of elongation - divided alr. getting bigger/aka longer (goal = reach water and nutrients)

3. zone of differentiation - when roothairs start forming (having spec. jobs @ this point)

intermediate growth

plant can grow throughout its life

determinate growth

some plant orgs. grow to a certain size then stop (leaves)

annuals

life cycle comp. in a year or less

biennials

req. 2 growing seasons

perennials

live for many years

meristematic tissue incl

meristems, apical meristems, leaf primordia, lateral meristems, vascular cambium, cork cambium, early/late wood, periderm, bark, primary growth, secondary growth, heartwood, sapwood

meristems

perpetually embryonic tissue and allows for indeterminate growth

• cont. actively dividing, undifferentiated cells

apical meristems

tips of roots and shoots and aux. buds of shoots // (elongate shoots + roots) which is primary growth (green!)

leaf primordia

formed from leaves along sides of apical meristem

aux. buds dev. meristematic cells left at bases of leaf promordia

lateral meristems

add thickness to woody plants, called secondary growth (brown/woody)

vascular cambium

“magic layer”

adds layers of vascular tissue called secondary xylem (growing to inside “wood”) and secondary phloem (growing to outside “bark”) —> grows in both directions to widen trunk

cork cambium

replaces the epidermis w/ peridem which is thicker and tougher

early wood

(growing to inside, secondary xylem)

made at the beginning of a growth season

maximizes water flow

spring

late wood

contributes to stem support

late summer

made at the end of a growing season

periderm

cork cambium plus the laters of cork cells it produces on outside

bark

all tissues external to the vascular cambium, inc. secondary phloem and periderm

secondary growth

in stems and roots of woody plants, rarely in leaves

characteristic of gymnosperms and many dicots but NOT monocots

secondary xylem accumulates as WOOD

heartwood

older (central) layers of secondary xylem, no longer transport water + minerals

sapwood

outer layers, still growing, still transporting materials through xylem