bio 2 - ch 30 plants (post)

plants

multicellular, photosynthetic eukaryotes; member of the supergroup Archaeplastida

• evolution marked by adaptations from water to land survival - internal vascular system

• other members of archaeplastida: red algae, green algae, and charophytes

the three categories of plants:

1. nonvascular (bryophytes)

2. Seedless vascular (lycophytes, ferns, and fern allies)

3. Seed plants (gymnosperms and angiosperms)

common characteristics that show evolutionary history of plants from green algae

1. have chlorophylls a and b and various accessory pigments

2. store excess carbs as starch

3. cellulose cell walls

closest related to charophyte green algae - the common ancestors are chara and coelchaete

challenges of evolution to land

• desiccation

• All reproductive stages (gametes, zygote, and embryo) must be protected from drying effects of air

• must develop structures to acquire and transport water

chara - ancestor of plants

• single file long cells anchored in mud

• Whorls of branches at regions called nodes

• Male and female structures grow at nodes

coleochaete - ancestor of plants

• Grows on flat, aquatic surfaces

• Used as a model organism in biotechnology studies

the five major evolutionary events that are adaptations to plants surviving on land

Development of

1. Embryo protection

1. Vascular tissue (transports water and nutrients)

2. Megaphylls - large leaves → photosynthesis

3. Seeds → protective coat and supportive nutrients

4. Flowers → give rise to fruit

alternation of generations

lifecycle has two different multicellular individuals that alternate to produce each other

• sporophyte (2n or diploid generation)

• gametophyte (n or haploid generation)

• one is dominant

  • in nonvascular plants gametophyte is dominant and in the other three sporophyte is dominant

    • sporophytes are the only ones with vascular tissue showing that this shift in dominance is an adaptation to life on land

• appearance of generations varies widely

sporophyte - alternation of generations

2n or diploid generation

• produces haploid spores via meoisis

  • a spore is a reproductive cell that can develop into a new organism without having to fuse with another cell

• spore undergoes mitosis to become gametophyte

gametophyte - alternation of generations

n or haploid generation

• Produces gametes (sperm and egg) by mitosis

  • Sperm and egg fuse to form a diploid zygote

  • Zygote divides by mitosis and becomes a diploid zygote to become a sporophyte

bryophytes and ferns appearance of generations

Gametophyte is small and independent

• Archegonia produce eggs, antheridia produce sperm

• Eggs fertilized by flagellated sperm, requiring water

seed plants appearance of generations

• Female gametophyte retained within sporophyte

  • Embryo sac within ovule

• Male gametophytes (pollen grains); don’t require water for transport

• Ovule becomes a seed after fertilization

nonvascular plants aka bryophytes

• Lack true roots, stems, and leaves

• Low-lying, with max height of only about 20 cm

• Have cuticle and complex tissues

• Gametophyte generation is dominant

• Flagellated sperm swim to the egg

• three divisions: hornworts, liverworts, mosses

liverworts - nonvascular plants/bryophytes

phylum Hepaticophyta

• two types: leafy and those with flat lobed bodies called thallus

• Merchantia are a type of thallus

  • smooth upper surface

  • rhizoids on lower surface

  • •Asexual and sexual reproduction

Marchantia liverwort reproduction

• Asexual reproduction by gemmae on upper surface - Groups of cells that detach and form new thallus

• Sexual reproduction:

  • Stalks have antheridia, where sperm are produced

  • Umbrella-headed stalks that bear archegonia, where eggs are produced

  • After fertilization, sporophytes begin growth in archegonia

hornworts - nonvascular plants/bryophytes

• mostly found in moist and shadey areas

• photosynthesize with small sporophytes - only one chloroplast per cell

• Have a symbiotic relationship with cyanobacteria, which can pull nitrogen from air

• Reproduce asexually through fragmentation → can bypass the alternation of generations life cycle with this method

mosses - nonvascular plants/bryophytes

phylum Bryophyta

• found in damp, shaded locations in the temperate zone but also can be in deserts and streams

• Can store large amounts of water but become dormant during dry periods

• produce asexually via fragmentation - Almost any part of the plant is able to grow thalli

• produce sexually with gametophyte being dominant

sexual reproduction of moss

• gametophyte is dominant

• dev in two stages: protonema forms first then becomes a mature gametophyte

  • rhizoid anchor thalli which bear antheridia and archegonia

    • the sporophyte is dependent on the gametophyte

  • The sporophyte consists of a foot that grows into the gametophyte

  • Develops a stalk and a capsule (sporangium)

  • The sporophyte is photosynthetic early; turns brown and nonphotosynthetic at maturity

  • Spores are released from the sporangium

    • •Spores germinate and produce a gametophyte in a new location

antheridium of plant reproduction

a sperm producer

uses of moss

can help convert rocks to soil to attract other organisms, can be used as fuel, can hold water, and can improve soil

seedless vascular plants

• have true roots, stems, and leaves

• vascular tissue: xylem and phloem

• The sporophyte is the dominant generation

  • diploid

• two groups: lycophytes and ferns and their allies

• produce windblown spores

• Small gametophytes produced when spores germinate

  • Independent of sporophyte for its nutrition

  • Flagellated sperm released by antheridia

  • Sperm swim in film of external water to archegonia

xylem of seedless vascular plants

conducts water and minerals; strong cell walls support plant body against gravity

phloem of seedless vascular plants

transports organic nutrients

archegonia for plant reproduction

the egg producer with one egg at base

lycophytes

phylum Lycophyta aka club mosses

• Among first land plants with vascular tissue

• Well-developed roots, stems, and leaves

  • Fleshy underground and rhizome

  • Scalelike leaves

  • Small leaves called microphylls with single vein

  • Sporangia borne on terminal clusters of leaves called strobili, which are club-shaped

• Highly flammable spores

• common in moist woodlands and in tropics and subtropics

rhizome

horizontal stem

ferns - seedless vascular

phylum Polypodiophyta

• lots of diversity - Most abundant in warm, moist tropical regions; also found in temperate areas

• leaves are called fronds and grow from rhizome

• •Dominant sporophyte stage produces windblown spores

• have true roots, stems, and leaves with vascular tissue

fern reproduction

• Spores germinate into gametophyte

  • Independent from the sporophyte

  • Dependent on water (lack vascular tissue)

  • Swimming sperm produced by antheridia and swim to archegonia

• At fertilization, a zygote develops into a sporophyte

  • Leaves of sporophyte start as fiddleheads that unroll

• Some ferns can spread into drier areas by asexual reproduction (vegetative)

  • Their rhizomes grow horizontally in soil, producing fiddleheads that become new fronds

whisk ferns - fern allies - seedless vascular plants

phylum Psilotophyta

• Arial stem with many forks

  • Attached to rhizome—underground stem

  • No leaves—photosynthesis occurs in stems

• Sporangia at ends of short branches produce spores

• Independent gametophyte found underground

• psilotum - no roots or leaves and yellow sporangia

horsetails - fern allies - seedless vascular plants

phylum Equisetophyta

• found in moist habitats worldwide

• Genus Equisetum

• Rhizome produces aerial stems

  • In some species, whorls of side branches come off the main stem at regions called nodes

• Leaves are scalelike and whorled at nodes

• Strobili are at the tips of stems in most

• Silica deposits found in cell walls

  • Called “scouring rushes

seed plants

includes: Gymnosperms (naked-seed plants) and angiosperms (flowering plants)

• most plentiful plants on Earth

• Seed contains a sporophyte embryo and stored food within protective seed coat

  • Allows an embryo to survive during long periods of dormancy

• Seeds germinate under favorable conditions

  • Stored food is the source of nutrition

• heterosporous - produce two types of spores

• produce two types of gametophytes

male gametophytes of seed plants are:

they are pollen grains

• Pollination—deposition of pollen on a female gametophyte

• Pollen tube—formed after pollen grain germinates and carries sperm; external water not needed for fertilization

  • Female gametophyte develops within ovule

gymnosperm - in seed plants

naked seeds

• Most are cone-bearing

• Ovules located on the surfaces of their cone scales - later becomes seeds

• Ovules not completely enclosed by diploid tissue

  • Unlike angiosperms that have covered ovules

• four groups: Conifers, cycads, ginkgos, and gnetophytes

conifers - types of gymnosperm seed plants

phylum Pinophyta

• evergren and cone bearing

• examples: Pine, spruce, fir, cedar, hemlock, and redwood

adaptations and uses of conifers

• Adapted to cold, dry weather such as northern temperate regions

• Needlelike leaves conserve water with thick cuticle and recessed stomata

• Dominant sporophyte produces two types of cones

  • pollen cones and seed cones

• wood uses in construction and to make paper

cycads - gymnosperm seed plants

phylum Cycadophyta

• Resemble palms or ferns with finely divided leaves that grow in clusters at the top of the stem

• Pollen or seed cones also at the top of the stem

• slow rate of growth puts them in danger of extinction

ginkgos - gymnosperm seed plants

phylum Ginkgophyta

• Female trees produce fleshy seeds that give off a foul odor

• Male trees are preferred for ornamental planting

• Resistant to pollution - do well in urban areas

gnetophytes - gymnosperm seed plants

three different living genera:

1. gnetum - in tropics → tress or climbing vines

2. ephedra - in southwestern NA and southeastern Asia → shrump with small scalelike leaves

3. Welwitschia - in deserts of southwestern Africa → has two large straplike leaves

angiosperms - seed plants

• phylum Magnoliophyta

• angio = vessel

• flowering plants

• lots of variety in appearance, sizes, and habitats

• seeds develop from an ovule within an ovary

  • overy becomes fruit

  • produces covered seeds

• hypothesized to have arose 200 MYA - coevolved with the insects that act as pollinators

monocots

Monocotyledones (Liliopsida)

• one cotyledon in their seeds

• Flower parts in threes or multiples of three

• usually herbaceous

• usually parallel venation

• scattere dbundes in stem

• fibrous root system

• pollen grain with one pore

cotyledon - flowering plants

seed that leaves that nourish the developing embryo

eudicots - flowering plants

Eudicotyledones

• two cotyledons in their seeds

• Flower parts in fours or fives or multiples of four or five

• Vascular bundles in a ring

• Woody or herbaceous

• Taproot system

• Usually net venation

• Pollen grain with three pores

common flower structures

• receptacles

  • bear the sepals, petals, stamens, and carpals

    • attached to receptacle in whorls

receptacle

tip of stalk that bears flowers

• Bears other flower parts that include sepals, petals, stamens, and carpels which attach via whorls

sepals

calyx - modified leaves that protect bud

petals

corolla - modified leaves, may be colorful

• diverse in size, shape, and color

• attract a particular pollinator

stamens

male reproductive structures

•Anther: pollen production

•Filament: stalk

carpel/pistil

female reproductive structures

stigma of a flower

place for reception of pollen

style of flower

elevates the stigma

ovary of flower

swollen base of carpel

•Contains one to hundreds of ovules

•Nectar produced near ovary

sexual reproduction of a flower

• dependent on species

• The flower produces both pollen and seeds

• Pollination can be by wind or pollinator

  • Nectar is provided to pollinators

  • Pollinators carry pollen between flowers of the same
    species

flowering plant life cycle

1. seed

2. mature seed

   1. mitsos

3. sporophyte

4. pollen sac

   1. male gametophyte: meiosis → microspores → pollen grain → pollenation

      1. mature male gamoetophyte

   2. female gametophyte: ovule → meoisis → megaspores → embryo sac

      1. mature female gamoetophyte

5. double fertilization

flowering plants with windblown pollen

•Not as showy or colorful as insect- or bird-pollinated flowers

•Night-blooming flowers

•Usually aromatic and white or cream-colored

•Smell alone attracts nocturnal pollinators, such as bats

fruits

the final product of a flower, aid in dispersal of seeds

•Dry fruits (pods) assist in the dispersal of windblown seeds

•Mature pods sometimes explode and shoot out the seeds

•Some pods (peas) simply break open to scatter seeds

•Dandelions produce a one-seeded fruit with branched hairs that are easily windblown

pinus staminate cone

male

• Cone is a modified shoot exhibiting a spiral arrangement of microsporophylls, each producing microspores that develop into winged pollen grains

pinus embryo

pinus ovule archegonium egg nucleus

lillium ovary

lilium anthers

pine pollen grains

fern young sporophyte

fern prothallium antheridia

• Small, spherical, or knob-like structures

• Usually found on the lower surface, often in the basal region

fern prothallium archegonia

• Located on the underside and generally situated near the notch (the "V" of the heart) on the thickest part of the thallus

• Flask-shaped, consisting of an elongated neck that projects outward and a venter (swollen base) embedded in the thallus tissue

• Has a single egg (gamete) located in the basal venter

fern sori

on the underside of fertile fronds, typically looking like brown-yellow spots or lines. Key microscopic traits include clusters of spore-filled sporangia, often protected by a specialized membrane called an indusium, which is surrounded by unique, thick-walled cells known as the annulus

moss antheridia

male reproductive organs

• multicellular structures found in clusters within the "splash cup" or apical rosettes of male gametophytes. looks like a club

• Produce and release biflagellate sperm

archegonial head

• flask-Shaped Structure - slender neck and a swollen basal portion

• The neck contains a row of neck canal cells that disintegrate at maturity to form a fluid-filled channel for sperm to swim toward the egg.

• Often surrounded by sterile, hair-like filaments called paraphyses that provide protection and help maintain moisture

• Because they are part of the gametophyte generation they are haploid

• Resembles a tiny, hanging palm tree, with THIS hanging down with their necks oriented downward

pollen cones life cycle

1. dev near tip of lower branches

2. two pollen sacs that lie on the underside of each scale

3. within the pollen sacs meiosis produces four microspores

4. each microspore becomes a pollen grain which has two wings and is carried by the wind to the see cone during pollination

5. the mature female gametophyte: only one of the megaspores undergoes mitosis and develops into a mature female gametophyte, having two-six archegonia. each archegonium has a single large egg lying near the ovule opening

6. the zygote: once a pollen grain reaches a seed cone it becomes a mature male gametophyte. a pollen tube digests its way toward the female and discharges two nonflagellated sperm and one will fertilize an egg in the archegonium resulting in a zygote

7. the sporophyte: after fertilization the ovule matures and becomes the seed composed of the embryo, reserve food, and a sed coat. the seed cone will be woody and hard after a while and opens to release winged seeds. when a seed germinates the sporophyte embryo develops into a new pine tree

seed cone life cycle

1. they are larger than their counterparts and are located near the tips of the higher branches

2. the ovules: the seed cone has two ovules that lie on the upper surface of each scale

3. the megaspore: within an ovule meiosis produces four megaspores but one survives

4. each microspore becomes a pollen grain which has two wings and is carried by the wind to the see cone during pollination

5. the mature female gametophyte: only one of the megaspores undergoes mitosis and develops into a mature female gametophyte, having two-six archegonia. each archegonium has a single large egg lying near the ovule opening

6. the zygote: once a pollen grain reaches a seed cone it becomes a mature male gametophyte. a pollen tube digests its way toward the female and discharges two nonflagellated sperm and one will fertilize an egg in the archegonium resulting in a zygote

7. the sporophyte: after fertilization the ovule matures and becomes the seed composed of the embryo, reserve food, and a sed coat. the seed cone will be woody and hard after a while and opens to release winged seeds. when a seed germinates the sporophyte embryo develops into a new pine tree

male pathway (microsporogenisis) angiosperm Flowering plant life cycle

starts as the Sporophyte (Diploid, 2n)

1. The mature flowering plant (tree) produces flowers containing both male (stamen) and female (carpel) structures

2. Anther contains pollen sacs (microsporangia)

3. Microspore mother cells undergo meiosis → produce microspores (haploid, n)

4. Microspores undergo mitosis → form pollen grains (immature male gametophytes) containing a tube cell and generative cell

5. Pollination transfers pollen grain to the stigma

6. The pollen grain becomes the mature male gametophyte, growing a pollen tube with 2 sperm cells

7. The pollen tube delivers 2 sperm into the embryo sac

8. Sperm #1 + egg → embryo (2n)

9. Sperm #2 + 2 polar nuclei → endosperm (3n) — nutrient tissue

10. The ovule matures into a seed (containing seed coat, embryo, and endosperm)

11. The ovary wall matures into the fruit

12. The seed germinates and the embryo grows via mitosis back into a new sporophyte

female pathway (megasporogenisis) angiosperm Flowering plant life cycle

starts as the Sporophyte (Diploid, 2n)

1. The mature flowering plant (tree) produces flowers containing both male (stamen) and female (carpel) structures

2. Ovule inside the ovary contains a megaspore mother cell

3. It undergoes meiosis → produces 4 megaspores, but 3 degenerate

4. The surviving megaspore undergoes mitosis → forms the embryo sac (mature female gametophyte)

5. The embryo sac contains: egg cell, polar nuclei, and other cells

6. Sperm #1 + egg → embryo (2n)

7. Sperm #2 + 2 polar nuclei → endosperm (3n) — nutrient tissue

8. The ovule matures into a seed (containing seed coat, embryo, and endosperm)

9. The ovary wall matures into the fruit

10. The seed germinates and the embryo grows via mitosis back into a new sporophyte

fern life cycle

Step 1: The Sporophyte (Diploid, 2n) - It has a rhizome (underground stem), roots, and fronds (leaves) that uncoil from fiddleheads

Step 2: The Sporangia — On the underside of the leaflets, sporangia are clustered into groups called sori (singular: sorus). Each sporangium has an annulus, a ring of thick-walled cells that helps launch spores

Step 3: The Spores (Meiosis → Haploid) — Inside each sporangium, meiosis occurs producing haploid (n) spores. When the sporangium opens, the spores are released into the environment

Step 4: The Gametophyte — A spore germinates and grows into a small heart-shaped prothallus (the gametophyte), which anchors with rhizoids and bears archegonia (female organs containing eggs) at the notch and antheridia (male organs producing sperm) near the rhizoids

Step 5: Fertilization — Fertilization requires moisture because sperm are flagellated and must swim from the antheridia to the egg inside the archegonium — this is why ferns depend on moist environments

Step 6: The Zygote (Back to Diploid, 2n) — The fertilized egg becomes a zygote that develops inside the archegonium, growing via mitosis into a young sporophyte on top of the gametophyte until its roots and first leaf allow it to become independent

Step 7: The Fronds — The sporophyte develops a root-bearing rhizome from which aerial fronds project upward, completing the cycle back to Step 1