Chapter 29, Plant Diversity

Plant evolution

The process by which plants evolved from green algae around 470 million years ago, developing features for life on land.

Sporopollenin

A polymer found in charophytes and plant spore walls that prevents zygotes from drying out.

Vascular plants

Plants that have specialized tissue (xylem and phloem) for the transport of water and nutrients.

Alternation of generations

A reproductive cycle in plants where there is a switch between multicellular haploid gametophytes and multicellular diploid sporophytes.

Apical meristems

Localized regions of cell division at the tips of roots and shoots that enable growth.

Bryophytes

A group of nonvascular plants that includes liverworts, mosses, and hornworts, characterized by dominant gametophytes.

Xylem

The vascular tissue in plants that conducts water and dissolved nutrients upward from the roots to the rest of the plant.

Phloem

The vascular tissue in plants that transports sugars and other metabolic products downward from the leaves.

Sporophylls

Modified leaves bearing sporangia, which are involved in the production of spores.

Homosporous

Plants that produce one type of spore that typically develops into a bisexual gametophyte.

Heterosporous

Plants that produce two types of spores, which develop into male and female gametophytes.

Lycophytes

A group of seedless vascular plants, including club mosses and their relatives.

Monilophytes

A group of seedless vascular plants that includes ferns, horsetails, and whisk ferns.

Angiosperms

Seed plants that produce seeds that develop inside flowers and are characterized by a high level of diversity.

Gymnosperms

Seed plants that produce 'naked seeds' not enclosed in chambers.

Protonema

A mass of green, branched, one-cell-thick filaments that develop from bryophyte spores.

Rhizoids

Root-like structures that anchor gametophytes to the substrate but do not absorb water or minerals.

Sphagnum

A type of moss that forms peat, a partially decayed organic material used as fuel.

Megaphylls

Larger leaves with a highly branched vascular system found in most plant groups except lycophytes.

Microphylls

Small, often spine-shaped leaves with a single vein, found only in lycophytes.