Chapter 26: Plants

Charophytes

Present day algae that share distinctive traits with plants, suggesting that it’s a close relative of plants

• Both have distinctive rings of proteins

• Similar sperm sturcture

• Sporopollenin to protect the zygotes

Sporopollenin

Layer of a durable polymer that prevents exposed zygotes from drying out

Alternation of generations

Switching between the gametophyte and the sporophyte phase

• Gametophyte: multicellular, creates the gametes (creates the egg and sperm)

• Sporophyte: mitotic division of the zygote creates this, and meiosis produces haploid spores, which turn into their own organism. Mitotic division of this spore cell produces a new multicellular gametophytes

Sporophyte

Has multicllular organs called “sporangia” that makes the pores.

Apical Meristems

Localized regions of cell division at the tips of roots and shoots. Can divide throughout the plant’s life, enabling its roots to elongate

Cuticle purpose

Water proofing; prevents excessive water loss from the aboveground plant organs

Hyphae

Network of filaments for fungus that provides it a large surface area which absorption can occur

Mycorrhizae

Plant-fungal symbiotic association allowing nutrients to be transferred from fungi to a plant partner

Fungi origin

Colonized land about the same time as plants, secrete enzymes that break down organic matter

Role of Chitin in Fungi

As a strong and flexible polysaccharide, it can absorb nutrients from the environment, and allows water to move into fungal cells through osmosis without bursting. The chitin maintains the strength of the cell.

Arbuscular mycorrhizal fungi

• Extend branching hyphae through the root cell wall and into tubes formed by invagination

Ectomycorrhizal fungi

Form unique sheaths of hyphae over the surface of a root and grows into the extracellular spaces of the root cortex

Sexual portion of a fungal life cycle

Plasmogamy:

• The cytoplasms of two parent mycelia fuse

Karyogamy:

• The haploid nuclei contributed by each parent fuses, producing a dipoid cell

***meiosis reverts them back to haploids

Bryophytes

Plants that lack an extensive transport system

• Liverworts, mosses, and hornworts (diverges from other plant lineages early in the history of plant evolution)

• Anchored to the ground by rhizoids

• Gametophytes are the dominant stage of life

• Typically live in moist environments

Seedless Vascular Plants

• Dominant sporophyte

• Lycophyte (club mosses and their relatives)

• Monilophytes (ferns and their relatives)

• Still requires water for fertilization

Xylem

• Conducts most of the water and minerals

• Includes tracheids, tube-shaped cells that carry water and minerals up from the roots

• Cell-walls strengthened by lignin

Phloem

Cells arranged into tubes that distribute sugars, amino acids, and other organic products

Roots

Organs that absorb water and nutrients from the soil, and anchor vascular plants to the ground

Leaves

• Serve as the primary photosynthetic organs of vascular plants

• Can be classified as either microphylls (small, spine-shaped leaves) or megaphylls (leaves with highly branched vascular systems)

Seed Plants

• Consists of an embryo and its food supply, surrounded by a protective coat

• Two major classifications: gymnosperms and angiosperms

Gymnosperms

Naked seed; not enclosed in any chamber

Angiosperm

Develop within the chambers called ovaries

Reduced gametophytes

• miniaturization of gametophytes shields them from UV radiation and protects them from drying out

• enables developing gametophytes to obtain nutrients from the parental sporophytes

Integument

• Sporophyte tissue layer that envelopes and protects the tissues that will eventually give rise to the female gametophyte

Ovule

The integument and the tissues it encloses together; in each ovule, an egg producing female gametophyte develops from a haploid spore

Megaspores

Produces the female gametophyte

Microspores

Produces the male gametophytes

Pollen Grain

• the male gametophyte, which is stored in a pollen wall

• Transported through wind or by hitchiking the body of an animal

Benefits of seeds

• Don’t require water to be transferred, unlike spores

• Seeds provide protection from harsher conditions

• Easily dispersed

• Have stored food supply

• Can stay dormant for a longer amount of time

Flowers purpose

Attracts insects or other animals to rub against the flower, thus transferring pollen from one flower to the sex organs on another flower

Sepals

Green and enclose the flower before it opens

Petals

The brightly colored parts than attract pollinators

Stamens

Produce pollen grains containing male gametophytes

Stamens

Produce pollen grains containing the male gametophytes

Anther

Direct place where the pollen is produced

Carpels

Make up the ovules, the container of the seeds

Stigma

Area that receives the pollen; sticky

Lichens

Symbiotic association between a fungus and a photosynthetic microorganism; important pioneers on cleared rock and soil surfaces as they can break down the surface

Ways plants impacts environment

• Affect formation of soil by holding soil in place

• Add nutrient to the soil

• Releases oxygen into the air as a by-product of photosynthesis

Endophytes

Live inside the leaves of other plant parts without causing them harm