The Life Cycle of Plants
Terms
Alternation of Generations
-
The fluctuation between the diploid (sporophyte) and haploid
(gametophyte)
life stages that occurs in plants.
Angiosperm
-
A vascular flowering plant in which seeds are enclosed inside of protective
ovaries.
Archegonium
-
The female sex organ of terrestrial plants; where egg cells are produced.
Bryophyte
-
A lower terrestrial plant (often a moss or liverwort) that lacks a vascular
system and is dependent
on environmental moisture for reproductive and nutritive functions.
Bulb
-
Roughly spherical underground bud containing additional buds that can develop
asexually into new plants. A form of vegetative propagation.
Cross-pollination
-
The process, occurring in most angiosperms, by which the male gametes of
one plant (carried by pollen grains) fertilize the eggs of another.
Diploid
-
Having two sets of chromosomes, one from each parent.
Double Fertilization
-
The mechanism of angiosperm fertilization that involves the joining of haploid
gametes to create
a diploid zygote, and the simultaneous joining of a second sperm cell with a
fusion
nucleus to create a triploid nucleus (which becomes endosperm).
Endosperm
-
A substance, formed from a triploid nucleus in angiosperm reproduction,
that nourishes a developing embryo within a seed.
Fragmentation
-
A form of vegetative propagation in which a severed plant part develops into
a whole new plant.
Fusion Nucleus
-
The diploid product formed by the joining of the two polar nuclei in the
angiosperm ovule.
Gamete
-
A haploid sex cell (either an egg or sperm cell); male and female gametes
join during fertilization to create a diploid zygote.
Gametophyte
-
A haploid plant or plant structure that produces haploid gametes through
mitosis.
Grafting
-
An artificial form of vegetative propagation in which parts of two young
plants are joined together, first by artificial means and then by tissue
regeneration.
Gymnosperm
-
A vascular non-flowering plant (commonly known as a conifer) in which seeds
are not protected by an ovary.
Haploid
-
Having only one set of chromosomes.
Heterospory
-
The reproductive phenomenon, characteristic of gymnosperms and
angiosperms, whereby spores of two distinct sexes are produced; these
spores develop into sex-specific gametophytes.
Megaspore
-
Female spore; gives rise to a female gametophyte.
Meiosis
-
Cell division that results in cells with half the chromosomes of the parent
cell.
Microspore
-
Male spore; gives rise to a male gametophyte.
Ovary
-
In plants, the protective structure that holds the ovules and surrounds the
angiosperm seed; after fertilization, develops into a fruit.
Ovule
-
Structure that contains the female gametophyte and gametes; after
fertilization, develops into a seed.
Pistil
-
The female reproductive organ of the flower, composed of a stigma,
style, and ovary; sometimes called
the carpel.
Polar Nuclei
-
Two nuclei, contained within the same cell, that are created from the
mitotic division of the megaspore during
angiosperm reproduction; unite in the ovule to form a fusion nucleus,
which gives rise to endosperm when fertilized.
Pollen Grain
-
The male gametophyte of gymnosperms and angiosperms.
Pollen Tube
-
The outgrowth of a pollen grain that creates a path through the female sex
organ in order to penetrate to the egg cells.
Runner
-
Slender horizontal stem that can give rise, via specialized nodes, to new
plants.
Scale Leaf
-
Very small structure on the surface of a tuber that contains a bud from
which a new plant can arise.
Scion
-
Twig or bud that is grafted onto a plant with roots (called the stock)
and develops into a new shoot system.
Self-pollination
-
The process by which the male gametes of a plant fertilize the eggs of the
same plant.
Sporangium
-
The part of a plant where spores are produced.
Spore
-
Haploid cell from which a gametophyte is produced.
Sporophyte
-
A diploid plant or plant structure that produces haploid spores through
meiosis.
Stigma
-
The top part of the pistil, where pollen grains are received.
Stock
-
Plant with a root system onto which a twig or bud from another plant (called a
scion) is grafted.
Tracheophyte
-
A terrestrial plant with a vascular system.
Triploid
-
Having three sets of chromosomes.
Tuber
-
Fleshy underground storage structure, composed of an enlarged portion of the
stem, that has on its surface buds capable of producing new plants.
Vascular System
-
Mechanism of internal water and nutrient transport, characteristic of
tracheophytes; made up of the vascular tissues
xylem and
phloem.
Vascular Tissue
-
A conductive component (either xylem or
phloem) of the system that transports food
and nutrients throughout the plant body.
Vegetative Propagation
-
A form of asexual reproduction in which plants produce genetically identical
offshoots (clones) of themselves, which then develop into independent plants.
Zygote
-
The diploid product of fertilization that develops into an embryo.
