Ch30 Reproduction and Domestication of Flowering Plants

ABC hypothesis

A model of flower formation identifying three classes of organ identity genes that direct formation of the four types of floral organs.

accessory fruits

A fruit, or assemblage of fruits, in which the fleshy parts are derived largely or entirely from tissues other than the ovary.

aggregate fruit

A fruit derived from a single flower that has more than one carpel.

anther

In an angiosperm, the terminal pollen sac of a stamen, where pollen grains containing sperm-producing male gametophytes form.

apomixis

The ability of some plant species to reproduce asexually through seeds without fertilization by a male gamete.

asexual reproduction

The generation of offspring from a single parent that occurs without the fusion of gametes.

biofuel

A fuel produced from biomass.

biomass

The total mass of organic matter comprising a group of organisms in a particular habitat.

callus

A mass of dividing, undifferentiated cells growing at the site of a wound or in culture.

carpels

The ovule-producing reproductive organ of a flower, consisting of the stigma, style, and ovary.

coevolution

The joint evolution of two interacting species, each in response to selection imposed by the other.

coleoptile

The covering of the young shoot of the embryo of a grass seed.

coleorhiza

The covering of the young root of the embryo of a grass seed.

complete flowers

A flower that has all four basic floral organs: sepals, petals, stamens, and carpels.

dioecious

In plant biology, having the male and female reproductive parts on different individuals of the same species.

dormancy

A condition typified by extremely low metabolic rate and a suspension of growth and development.

double fertilization

A mechanism of fertilization in angiosperms in which two sperm cells unite with two cells in the female gametophyte to form the zygote and endosperm.

endosperm

A nutrient-rich tissue formed by the union of a sperm with two polar nuclei during double fertilization.

epicotyl

In an angiosperm embryo, the embryonic axis above the point of attachment of the cotyledon(s) and below the first pair of miniature leaves.

fertilization

The union of haploid gametes to produce a diploid zygote.

fragmentation

A means of asexual reproduction whereby a single parent breaks into parts that regenerate into whole new individuals.

fruit

A mature ovary of a flower that protects dormant seeds and often aids in their dispersal.

hypocotyl

In an angiosperm embryo, the embryonic axis below the point of attachment of the cotyledon(s) and above the radicle.

imbibition

The uptake of water by a seed or other structure, resulting in swelling.

incomplete flowers

A flower in which one or more of the four basic floral organs are either absent or nonfunctional.

inflorescences

A group of flowers tightly clustered together.

megaspores

A spore from a heterosporous plant species that develops into a female gametophyte.

microspores

A spore from a heterosporous plant species that develops into a male gametophyte.

multiple fruit

A fruit derived from an entire inflorescence.

ovary

In flowers, the portion of a carpel in which the egg-containing ovules develop.

ovules

A structure that develops within the ovary of a seed plant and contains the female gametophyte.

petals

A modified leaf of a flowering plant, often colorful, advertising the flower to pollinators.

pistil

A single carpel (simple pistil) or a group of fused carpels (compound pistil).

pollen grain

In seed plants, a structure consisting of the male gametophyte enclosed within a pollen wall.

pollen tube

A tube that forms after germination of the pollen grain, delivering sperm to the ovule.

pollination

The transfer of pollen to the part of a seed plant containing the ovules.

radicle

An embryonic root of a plant.

receptacle

The base of a flower; the part of the stem that is the site of attachment of the floral organs.

scion

The twig grafted onto the stock when making a graft.

seed

An adaptation of some terrestrial plants consisting of an embryo packaged with a store of food within a protective coat.

seed coat

A tough outer covering of a seed that protects the embryo and endosperm.

self-incompatibility

The ability of a seed plant to reject its own pollen.

sepals

A modified leaf in angiosperms that helps enclose and protect a flower bud.

simple fruit

A fruit derived from a single carpel or several fused carpels.

stamens

The pollen-producing reproductive organ of a flower, consisting of an anther and a filament.

stock

The plant that provides the root system when making a graft.

style

The stalk of a flower’s carpel, with the ovary at the base and the stigma at the top.

totipotent

Describing a cell that can give rise to all parts of the embryo and adult.

transgenic

Pertaining to an organism whose genome contains DNA introduced from another organism.

vegetative propagation

Cloning of plants by humans.

vegetative reproduction

Cloning of plants in nature.

Why can xylem transport water and minerals using dead cells, whereas phloem requires living cells?

Because xylem is passive

Positive pressure, whether it be in the xylem when root pressure predominates, or in the sieve tube elements of the phloem, requires active transport. Most long distance transport in the xylem depends on bulk flow driven by negative pressure potential generated ultimately by the evaporation of water from the leaf and does not require living cells.