biology chapter 26 - land plants

a single species of freshwater algae..

gave rise to the entire terrestrial plant lineage.

charophytes

a division of freshwater green algae

cuticle

a waxy, water-impermeable substance that reduce water loss due to evaporation

• limits the exchange of gas needed for photosynthesis and cellular respiration

• plant compensates by evolving a stoma

• 
  

stomata

tiny, mouth shaped openings on a plant surface that allow gas exchange to occur. can be closed to limit water loss

UV…

can be damaging to plants

• production of pigments can absorb harmful UV light

bryophytes

the most primitive of the land plants, cant grow beyond a certain height because they lack vasculature to efficiently transport water

tracheophytes

more advanced, have specialized vascular tissue for transport over long distances (xylem)

• a group of 7 phyla of plants that possess vascular tissue

  • more spores produced

  • dominant sporophyte generation

  • appearance of vascular tissue

  • better regulates gas exchange

xylem and phloem…

both also provide support

sporophyte

make spores in sporangia where spore mother cells (sporocytes) undergo meiosis to produce 4 haploid spores.

gametophytes

produce haploid gametes that fuse to restore the diploid state into a zygote

transition from water to land includes

• ways to limit water loss and control gas exchange

• ways to limit damage to DNA by ultraviolet light

• ways to transport water through the body of a plant

• tissues to resist the effects of wind and gravity

• ways to protect and distribute reproductive structures

• life cycles that promote genetic diversity

basic alterations of generations

during early evolution of plants…

the haploid generation was the more dominant stage and usually were gametophytes

sporophytes in moss

nutritionally dependent on the gametophyte (dominant generation)

what phase is more visible in tracheophytes?

sporophyte phase is more visible

bryophytes

the closest living descendents of the first land plants. considered to be non-vascular made up of

• the liverworts

• the mosses

• the hornwarts

several similarities to modern relatives, including

• gymnosperms

• angiosperms

usually are pretty short bc of lack of vascular tissue

lack roots, instead have primitive anchoring systems called rhizoids that can absorb water

gametophyte is the dominant generation

vascular plants

have specialized internal tubes (xylem and phloem) to transport water and food

nonvascular plants

lack these tissues and absorb nutrients directly through their cells

rhizoids

bryophytes primitive anchoring systems. consists of several cells that absorb water, but not nearly the volume of water that is absorbed by a vascular plant root

archegonia

multicellular, flask-shaped female reproductive organs found in the gametophyte phase of bryophytes (like mosses), seedless vascular plants (like ferns), and some gymnosperms (like conifers)

antheridia

haploid, male reproductive organs that produce and store motile sperm cells in non-flowering plants, algae, and some fungi

moss reproductive cycle

antheridium

a haploid sex organ that produces and stores male gametes (sperm cells or antherozoids) in algae, fungi, bryophytes, and seedless vascular plants like ferns

sporangium

where spores are stored

where is moss most abundant?

arctic and antarctic

when did the first plant with vasculature show up

420 Mya

xylem

tissue that conducts water and dissolved minerals upwards from the roots

phloem

conducts sucrose and hormones throughout the plant

vascular tissue is what…

allows tracheophytes to be large

vascular tissue is formed…

during sporophyte phase

3 clades of tracheophytes

• lycophytes

• monilophytes

• seed plants

true roots (only in tracheotphytes)

a plant organ that develops directly from the embryonic radicle during seed germination and contains vascular tissue (xylem and phloem)

phylum monilophyta

seedless vascular plants

• contains sperm and egg

euphyllophytes

Euphyllophytes are a major clade of vascular plants (tracheophytes) that comprise over 95% of all living plant species, characterized by the presence of true leaves. have distinct origins from lycophylls

lycopsid

an ancient class of spore-bearing vascular plants commonly known as clubmosses and firmosses

leaves allowed

more photosynthesis capacity

lycophylls

single vascular strands supporting relatively small leaves of lycophylls

euphylls

true leaves (only found in ferns and seed plants)

fern reproductive cycle

more fern bs

• the fern embryo shows a distinct transition in the evolution of land plants

• the fern embryo, in the archegonium, has substantially more protection from the environment than does a charophyte zygote

• but fern embryo cannot enter a dormant phase to survive harsh winter the way a seed plant embryo can

seed producing plants have…

dominated terrestrial landscape

• 400,000+ species

• seeds allow embryos to pause development and growth and then germinate after a harsh winter or dry season

• fruits made seeds easier to disperse

integument

and extra layer of sporophyte tissue that protects embryos

ovule

the female reproductive structure in seed plants that contains the egg cell and develops into a seed after fertilization

megasporangium

a plant reproductive structure that produces megaspores (female spores)

haploid megaspore

s a specialized female spore produced in heterosporous plants (such as seed plants and certain ferns) that develops into the female gametophyte

pollen grain

multicellular male gametophyte that produces sperm cells by mitosis.

pollen tube

a tubular structure produced by the male gametophyte of seed plants when it germinates. (sperm to egg)

4 groups of gymnosperms

• conifers

• cycads

• gametophytes

• ginkgo

gymnosperms characteristics

• lack fruit and flowers

• the ovule, which becomes a seed, rests exposed on a scale (modified shoot or leaf), not completely enclosed by sporophyte tissue (integument) at the time of pollination

gymnosperm means…

“naked seed”

conifers are…

the largest gymnosperm phylum

life cycle of a pine

all seed plants produce…

two types of spores that give rise to two type of gametophytes

• male gametophyte - pollen grains - develop from microspores, which are produced in malew cones that develop in clusters of 30 - 70 at the tips of lower branches

• female pinecones - typically are produced on the upper branches of the same tree that produces male cones. female cones are larger and their scales become woody

how long do female cones take to mature?

2+ seasons

while the female cones are open…

pollen grains carried by the wind drift down between them, some catching in sticky fluid oozing out of the microphyte

• the pollen grains within the sticky fluid are slowly drawn down through the micropyle to the top of the nucleus, and the scales close shortly after

angiosperms

a group of seed plants of about 300,000 species of flowers

• unlike gymnosperms, angiosperms have ocules that are enclosed within diploid tissue at the time of pollination

carpel

modified leaf that encapsulates seeds, develops into fruit, a unique angiosperm feature

angiosperm 2 main clades

• eudicots - the largest group of flowering plants, making up about 75% of all angiosperm species

  • Pollen: Features distinct pollen grains with three or more pores or grooves (tricolpate).

  • Seed Leaves: Seeds typically contain two cotyledons (embryonic seed leaves).

  • Leaves and Roots: Leaves generally have a net-like (reticulate) venation pattern, and plants often feature a main taproot system.

  • Floral Parts: Flower parts are usually arranged in multiples of four or five.

  • Stems: Vascular bundles in the stem are arranged in a ring around a central pith. [1, 2, 3, 4]

• monocots - a major group of flowering plants defined by seeds that contain a single embryonic leaf, or cotyledon.

  • Seed Leaf: The embryo inside the seed has only one cotyledon.

  • Leaf Veins: The veins run parallel to each other from the base to the tip.

  • Stem Structure: Vascular bundles (the plant's transport tissues) are scattered throughout the stem rather than forming a neat ring.

  • Root System: They have a fibrous root system made of adventitious roots that spread out near the surface instead of a single deep taproot.

  • Flowers: Petals, sepals, and other flower parts usually appear in multiples of three.

  • Growth: Most monocots lack true secondary growth or woody bark, though exceptions like palm trees can grow tall. [1, 2, 3, 4, 5]

eudicots

the largest group of flowering plants, making up about 75% of all angiosperm species

• Pollen: Features distinct pollen grains with three or more pores or grooves (tricolpate).

• Seed Leaves: Seeds typically contain two cotyledons (embryonic seed leaves).

• Leaves and Roots: Leaves generally have a net-like (reticulate) venation pattern, and plants often feature a main taproot system.

• Floral Parts: Flower parts are usually arranged in multiples of four or five.

• Stems: Vascular bundles in the stem are arranged in a ring around a central pith. [1, 2, 3, 4]

monocots

a major group of flowering plants defined by seeds that contain a single embryonic leaf, or cotyledon.

• Seed Leaf: The embryo inside the seed has only one cotyledon.

• Leaf Veins: The veins run parallel to each other from the base to the tip.

• Stem Structure: Vascular bundles (the plant's transport tissues) are scattered throughout the stem rather than forming a neat ring.

• Root System: They have a fibrous root system made of adventitious roots that spread out near the surface instead of a single deep taproot.

• Flowers: Petals, sepals, and other flower parts usually appear in multiples of three.

• Growth: Most monocots lack true secondary growth or woody bark, though exceptions like palm trees can grow tall. [1, 2, 3, 4, 5]

cotyledons

an embryonic "seed leaf" inside a plant's seed that provides essential nutrients and energy during germination before true leaves develop

• monocots - 1

• eudicots - 2

hypothesis of angiosperm takeover

break up of pangea lead to climate change and opportunities for the angiosperm expansion.

• aided by flower production, pollinators, and broad leaves and dense veins

flowers

improved effeciency of pollination, variety of breeding systems promotes genetic diversity

reduced gametophytes (angiosperms)

faster seed production; reduced resource allocation to gametophyte generation

carpels

female reproductive unit of a flowering plant (angiosperm), consisting of an ovary, a style, and a stigma

endosperm (angiosperm)

provides nutrients for developing embryo

vasculature

vessel elements allow more efficient water transport than do the trachieds of gymnosperms

premordium

an early group of cells or tissue in a flowering plant that develops into a flower (all flowers have)

pedical

the bud the premordium develops into. expands slightly at the tip to form the receptacle

receptacle

the thickened, enlarged top of a flower stalk (pedicel or peduncle) where the parts of a flower are attached. Develops from pedical

whorls

flower parts attached in circles

sepals

outermost whorl that are green and leaflike

petals

often colored, attracting pollinators such as insects, birds, bats, monkeys, and small mammals

stamens

where the male gametophytes, pollen, is produced

anther

pollen producing part of a flower’s male reproductive organ

gynoecium

the innermost whorl and female reproductive part of a flowering plant. where small female gametophytes are housed, has 1+ carpels

the 4 layers of flowers

1. sepals

2. petals

3. stamens

4. carpels or pistils

first carpel is believed to have…

been formed by leaflike structure with ovules along it’s margins

carpels then vs now

first carpel is believed to have been formed by leaflike structure with ovules along it’s margins

structure of carpel

• ovary - swollen bvase, contains 1 - 100 ovules, later develops into a fruit

• stigma - tip of carpel. most are sticky

• style - connects stigma and ovary

nectar

often located towards the base of the ovary. a fluid containing sugars, amino acids, and other molecules that attracts insects, birds, and other animals to flowers

angiosperm life cycle

flower structure

female angiosperm reproduction

1. ovule (has protective coating called integument) (also has small hole for pollen tube called micropyle) (2n)

2. meiosis

3. now we have 4 haploid (n) megaspores, 1 of which survives

4. mitosis x3 (double fertilization) (8 haploid) (n)

5. left with 1 egg cell and 2 synergids (help guide egg)(3), 3 useless ones (3), and 1 cell with 2 polar nuclei (forms endosperm) all n

synergids

two specialized, supportive cells located in the female gametophyte (embryo sac) of flowering plants (angiosperms

male angiosperm reproduction

1. Anther (2n) microspore mother cells form (2n) (provide nutrition for developing pollen)

2. meiosis

3. 4 microspores (n). initially remain together in tetrad or quartet

4. mitosis

5. separate from tetrads, develops a protective, two layered wall. now they are pollen grains. Also have aperatures, where pollen tube can emerge. wall -

   1. exine - tough outer layer

   2. intine - inner layer that helps form pollen tube

6. anther matures, walls break down, pollen released

aperatures

where pollen tube can emerge

pollination

the transfer of pollen from ut’s source (anther) to a receptive area (stigma)

how often does self-pollination happen?

¼ of the time in angiosperms

recieving pollen

• if the stigma is receptive, the pollen grain’s dense cytoplasm absorbs substances from the stigma and bulges through an aperature

• the bulge develops into a pollen tube that responds to mechanical and chemical stimuli that guide it to the embryo sac.

• it follows a diffusion gradient of the chemicals and grows down through the style and into the micropyle

• pollen tube takes several hours to 2 days to reach the micropyle

• pollen tube faster in angiosperms than gymnosperms

sperm in angiosperms

have no flagella