Plant Diversity and Function

Four key events in plant history

1. Origin of land plants, 2. Origin of vascular plants, 3. Origin of seed plants, 4. Origin of flowers.

Plant ancestors

Green algae, which are protists.

Challenges of living on land

Drying out, obtaining resources from two sources, structural support, and reproduction/dispersal.

Waxy cuticle

An evolutionary adaptation in plants to keep from drying out on land.

Stomata

Tiny pores in plant leaves that open and close to let CO2 in and O2 out.

Xylem

Vascular tissue that transports water and minerals upward from roots in a unidirectional flow.

Phloem

Vascular tissue that distributes food and nutrients in a bidirectional flow.

Alternation of generations

An alternation between haploid sexual (gametophyte) and diploid asexual (sporophyte) phases in a plant life cycle.

Nonvascular plants (Bryophytes)

Gametophyte-dominant plants (e.g., mosses) lacking true roots, leaves, and lignin; require water for reproduction.

Seedless vascular plants

Sporophyte-dominant plants (e.g., ferns) with true roots, leaves, vascular tissue, and lignin; require water for fertilization.

Gymnosperms

Cone-bearing seed plants with naked seeds that do not produce fruit.

Angiosperms

Flowering plants that produce enclosed seeds within a protective fruit.

Carpel

The female reproductive part of a flower that receives pollen.

Stamen

The male reproductive part of a flower that produces pollen.

Fruit

Modified ovaries that develop after angiosperm seeds are fertilized.

Bird pollination syndrome

Flowers that are bright red and orange with no scents, adapted for bird pollinators.

Bee pollination syndrome

Flowers marked with ultraviolet (UV) guides that lead bees to nectar.

Bat and moth pollination syndrome

White, highly scented flowers that bloom at night for nocturnal pollinators.

Wind pollination syndrome

Small, green flowers with no showy petals, no scents, and feathery stigmas.

Sphagnum moss economic and ecological value

Crucial for global carbon storage in peatlands, used as fuel, bandages, and for giving scotch its smoky flavor.

Sporopollenin

A durable polymer that prevents exposed zygotes from drying out, found in plant spores and pollen grains.

Mycorrhizae

Mutualistic associations between fungi and plant roots that helped early plants absorb nutrients.

Apical meristems

Localized regions of cell division at the tips of roots and shoots that allow plants to grow in length.

Double fertilization

A process in angiosperms where one sperm fertilizes the egg and another combines with the central cell to form endosperm.

Endosperm

A nutrient-rich tissue formed during double fertilization that provides food for the developing angiosperm embryo.

Lignin

A complex organic polymer that hardens cell walls in vascular plants, providing structural support to grow tall.