Comprehensive Botany and Plant Evolution

Anthocyanins

Pigments produced by plants to prevent damage from solar radiation and herbivores.

Hydrostatic skeleton

The rigid structural support of land plants resulting from internal turgor pressure acting on tough cellulose-based cell walls from the water-filled cell inside.

Lignin

A very tough polymer used by plants to structurally reinforce certain cell walls.

Roots

One of the main organ systems in vascular plants that anchor the plant in a substrate, extract water and nutrients, and transport them to the rest of the plant.

Holdfast

A structure in algae that secures them to a particular spot.

Rhizoids

Simple root-like structures in nonvascular plants that anchor them to a substrate but do not transport water or nutrients.

Gametes

Sex cells. Usually haploid cells, male and female, that fuse during fertilization to form a zygote.

Photosynthesis

A biological reaction that uses energy from light to convert carbon dioxide into organic molecules, like sugars.

Cyanobacteria

A group of bacteria (prokaryotes) that were the first oxygen-producing photosynthetic life on Earth that increased the oxygen content of the atmosphere.

Oxygen Revolution

The mass-oxygenation of Earth's atmosphere around 2.5 billion years ago caused by the photosynthetic activity of cyanobacteria.

Embryophyte

The true land plants, united by certain specialized traits.

Charophytes

A group of green algae that are the closest living lineage to the land plants (embryophytes).

Green Algae

A group of photosynthetic eukaryotic organisms that are distantly related to true land plants (embryophytes).

Sporopollenin

A tough polymer employed by both algae and plants to encase reproductive cells to protect them from drying out.

Meiosis

A type of cell division that produces four haploid daughter cells from a single diploid cell.

Zygote

A new, diploid organism resulting from the fusion of haploid gametes during fertilization.

Diploid

An organism whose cells have two complete sets of chromosomes in their nuclei, abbreviated as 2n.

Haploid

An organism whose cells have one complete set of chromosomes in their nuclei, abbreviated as n.

Sperm

The male gamete. Usually haploid and smaller than the egg.

Egg

The female gamete. Usually haploid and larger than the sperm.

Mitosis

A type of asexual cell division that produces two genetically identical diploid daughter cells from a single diploid cell.

Sporangium

A part of the sporophyte that produces spores by meiosis.

Spore

A single haploid cell produced by a sporophyte through meiosis.

Sporophyte

A stage in the lifecycle of plants and certain algae that exists as a multicellular, diploid organism that produces spores by meiosis.

Gametangium

The part of the gametophyte that produces gametes by mitosis.

Gametophyte

A stage in the lifecycle of plants and certain algae that exists as a multicellular, haploid organism that produces gametes by mitosis.

Bryophytes

A commonly used but scientifically flawed grouping of all the nonvascular land plants (embryophytes) that includes mosses.

Seedless Vascular Plants

A grouping of vascular plants that do not produce pollen or seeds, and instead disperse via spores.

Gymnosperms

Cone-bearing plants; the group of vascular seed plants that produce pollen and seeds in cones.

Angiosperms

Flowering plants; the group of vascular seed plants that produce flowers and fruit.

Apical meristem

Regions of continuous cell division at the tips of shoots and roots that are responsible for primary growth.

Waxy cuticle

A waterproof lipid layer coating the surfaces of land plants to minimize water loss to evaporation.

Stomata

Pores in a plants' epidermis that allow for gas movement and transpiration in and out of the plant.

Vascular Plants

The group that includes all living land plants except the bryophytes.

Cone

The reproductive structure of a gymnosperm that produces pollen (male) or ovules (female).

Pollen

A tiny, tough-shelled granule produced by the cones or flowers of seed plants that contains the male gametophyte.

Megaspore

The 'large' haploid spore of seed plants that gives rise to the female gametophyte.

Microspore

The 'small' haploid spore of seed plants that gives rise to the male gametophyte.

Pollination

The movement of pollen to a receptive part of a plant where it can fertilize an egg cell.

Seed

Dispersive structures produced by gymnosperms and angiosperms from ovules following their fertilization.

Embryo

The underdeveloped, multicellular sporophyte plant inside of a seed before germination.

Seed coat

The protective shell of a seed formed from the integument tissue around the ovule.

Ovary

The female structure at the base of the carpel in a flower that contains the ovules and matures into a fruit.

Flower

The reproductive structure of an angiosperm sporophyte in which the male and/or female gametophytes are produced.

Fruit

An angiosperm structure formed from the flower's ovary following the fertilization of the ovules.

Receptacle

A swelling of the shoot at the base of a flower to which the flower parts are attached.

Sepal

A part of a flower derived from highly modified leaves that is external to the petals.

Petal

A part of a flower derived from highly modified leaves that usually serves to visually attract animal pollinators by displaying colors.

Stamens

The male reproductive structures of a flower.

Anther

The meiotically-active part of the angiosperm stamen (male organ) that houses the microspores and eventually splits to release mature pollen.

Filament

A part of the angiosperm stamen (male organ) that is the stalk supporting the anther.

Carpel

The entire female reproductive structure of a flower.

Ovules

Sac-like structures inside a flower's ovary that hold the female gametophyte.

Style

Part of the carpel (female organ) of a flower; a stalk extending up from the ovary and ending in a stigma.

Stigma

Part of the carpel (female organ) of a flower; the wide tip at the end of the style which receives pollen.

Pollen tube

The elongating tube cell of a pollen grain that contains the generative cell and grows down a flower's style towards the ovules.

Embryo Sac

The female gametophyte of an angiosperm located inside an ovule consisting of eight haploid cells.

Integument

The layered sporophyte tissue forming the outside of the ovule.

Micropyle

An opening in the integument of an ovule through which a pollen tube can enter to fertilize the embryo sac inside.

Synergid cell

Two haploid, single-nucleated cells present in an angiosperm's female gametophyte at the micropylar end alongside the egg cell.

Antipodal cell

Three haploid, single-nucleated cells present in an angiosperm's female gametophyte opposite the micropylar end.

Polar nuclei

The two haploid nuclei of the central cell of the embryo sac.

Tube cell

One of two cells of the male gametophyte in seed plants, found inside the pollen.

Generative cell

One of two cells in a pollen grain, found inside the tube cell.

Double fertilization

The fertilization process in angiosperms where two sperm cells are formed.

Endosperm

A triploid tissue within an angiosperm seed that stores nutrients for the developing plant embryo.

Cotyledon

Seed leaves; embryonic structures in a seed that may be the first leaf-like structures to emerge.

Monocots

A classification of flowering plants characterized by having a single cotyledon.

Dicots

A no-longer valid classification of flowering plants characterized by two cotyledons.

Shoots

One of the main organ systems in vascular plants, consisting of stems and leaves.

Radicle

The embryonic root that germinates from a seed and gives rise to the plant's root system.

Hypocotyl

The embryonic shoot that emerges from a seed.

Coleoptile

A hollow sheath-like structure found in monocots that emerges from the seed as the beginning of a shoot system.

Primary Growth

The development of new tissues in a plant through cell division that causes plant structures to get longer.

Secondary Growth

The development of new tissues in certain plants through cell division that causes roots and shoots to grow wider.

Determinate Growth

Growth of an organism that has genetically predetermined limits in terms of size or number of structures.

Indeterminate Growth

Growth of an organism that lacks genetically predetermined limits in terms of size or number of structures.

Primary Root

The original, often main, mature root of a plant that develops from the radicle.

Lateral Root

A root that branches from the primary root produced by its primary growth.

Fibrous Root System

A root system with many finely divided roots and no main central taproot.

Taproot

A root system with a large, usually thick primary root and many smaller lateral roots.

Root hair

Cellular extensions of active parts of the root that increase the surface area of the root.

Stem

A stalk-like vascular part of the shoot system that supports leaves and flowers.

Leaf

Part of the shoot system that is usually responsible for most of a plant's photosynthesis.

Petiole

The leaf stalk by which the leaf connects to the stem.

Leaf blade

The main body of a leaf usually consisting of a flat, broad surface.

Reproductive shoots

In angiosperms, the fertile flower-bearing shoots.

Vegetative shoot

The sterile shoots that do not produce structures for sexual reproduction.

Axillary meristem

The buds located within the axil that are usually inactive but have the potential to produce a lateral shoot.

Nodes

The places along the shoot from which leaves branch off.

Internodes

Segments of the shoot in between nodes.

Rhizome

An underground shoot that grows and branches horizontally, often helping a plant colonize an area.

Tuber

An underground shoot that swells to form a storage organ. It can also produce new plants through asexual reproduction.

Stolon

An above-ground shoot that extends away from the parent plant, spreading horizontally over the ground with new plantlets growing along its length as an asexual reproductive strategy. Also informally called a runner.

Margin

The edge of a leaf blade.

Leaf tip

When present, it is the part of the leaf blade where the margins meet at a point; the narrowest part of the leaf.

Axil

The space in the angle between a stem and the petiole of a leaf growing out of it.

Trichome

Hair-like structure on a plant's epidermis.

Bulb

Underground storage organ found in some plants that is derived from modified nonphotosynthetic leaves.

Dermal tissue

One of the three tissue types in plants. A protective, external layer of cells that functions as the barrier between the inside of the plant and the environment outside of it.