Plant Reproduction and Development ACE BIO

Flowers

the complex, reproductive structures of angiosperms; they are clusters of highly modified leaves.

Pollination

the transfer of pollen grains between the flowers of different plants of the same species.

Pedicel (Peduncle)

the shortened stem of a flower; all of the flower's modified leaves are attached to the pedicel; if more than one flower is attached to this “stem”, it is called a pedicel; if only one flower is attached, it is called a peduncle.

Receptacle

the widened end of the pedicel, which forms the base of the flower.

Sepals

small leaves at the base of the flower.

Calyx

a flower's collection or group of sepals.

Petals

the brightly colored or patterned leaves of a flower.

Corolla

a flower's collection or group of petals.

Stamens

the male reproductive structures of a flower.

Filament

the slender stalk of stamens.

Anthers

the enlarged, upper portion of a stamen; pollen grains are produced inside and released from each one.

Carpel (Pistil)

the female reproductive structures of a flower.

Stigma

the sticky, flattened area at the top of the carpel; it attracts and causes pollen to stick to it.

Style

the long, usually slender, tube of the carpel that connects the stigma with the ovary.

Ovary

the enlarged bottom part of the carpel; egg gametes are produced within the ovary.

Ovules

the individual, highly protected structures within the ovary portion of the carpel; eggs are produced within each ovule.

Nectaries

glands within the stigma that secrete a sugary “nectar” that attracts pollinators because of its scent and because it can be used as a food source for most pollinators.

Pollinators

any organism that naturally performs pollination for various plant species; most are insects.

Microspores

haploid, “male” spores produced in the anthers of stamens.

Microgametophyte

the male gametophyte of angiosperms; it is a haploid, two-cell pollen grain.

Generative cell

one of two cells of a pollen grain; it will divide by mitosis to produce 2 sperm cells each.

Tube cell

one of two cells of a pollen grain; develops into a pollen tube, which will direct and guide the sperm toward the egg.

Integuments

one or two protective layers of tissue that surround each ovule within the ovary.

Micropyle

single, small opening in the integuments; to fertilize the egg, sperm must enter the ovule through the micropyle.

Megaspores

haploid, “female” spores produced in the ovules of carpels. Ovules are located in the ovary portion of the carpel.

Megagametophyte

the female gametophyte of angiosperms; it is a haploid, 7-cell embryo sac.

Endosperm mother cell

one of the 7 cells of the embryo sac; it contains 2 nuclei.

Polar nuclei

the 2 nuclei of the endosperm mother cell.

Fertilization

the fusion of egg and sperm nuclei.

Zygote

the diploid cell that results from fertilization; a zygote develops when one of the two sperm cells from the generative cell of a pollen grain fertilizes the egg cell of the embryo sac.

Primary endosperm cell

the triploid (3n) cell that results when the other sperm cell from the generative cell of a pollen grain fuses with the 2 polar nuclei of the endosperm mother cell.

“Double fertilization”

term used to describe the process in which both sperm cells of the generative cell of a pollen grain fuse with some portion of the embryo sac (i.e., the egg cell and the polar nuclei).

Embryo

the larger, diploid organism that results from further mitotic divisions of the zygote.

Cotyledons

the main part of the plant embryo within the seed; the first structures to begin photosynthesis.

Epicotyl

portion of the plant embryo that lies above the cotyledons; it will develop into the plant's shoot system.

Hypocotyl

portion of the plant embryo that lies below the cotyledons; its tip portion becomes the root system.

Radicle

tip portion of the hypocotyl that will develop into the plant's root system; first to emerge from the seed.

Suspensor

cells that connect the embryo with the endosperm; transports nutrients from the endosperm to the growing embryo.

Seeds

structures that completely contain and protect the developing embryo and its endosperm; it forms from the ovule; there is one embryo per seed.

Endosperm

an important tissue that develops from the 3n primary endosperm cell; it surrounds and nourishes the embryo and growing seedling during the early part of its life.

Seed coat

the outer, protective layer of the seed; it develops from the ovule integuments.

Fruit

dry or fleshy structure that completely contains and often protects all of a flowers seeds; it forms from the ovary and functions to disperse the plant’s seeds.

Fruit and seed dispersal

the various processes plants use to spread out their fruits and seeds throughout their habitat in order to reduce competition among embryos and seedlings.

Vegetative reproduction

type of asexual reproduction plants use in order to produce certain asexual structures; those structures produced this way are called vegetative structures.

Runners (or stolons)

an example of a vegetative structure; horizontal stems that grow on the surface of soil.

Rhizomes

an example of a vegetative structure; horizontal, underground stems.

Bulbs

an example of a vegetative structure; they are modified, compact stems with fleshy leaves.

Tubers

an example of a vegetative structure; they are enlarged, underground stems.

Leaf shoots

asexual offspring that develop from normal leaves.

Parthenocarpy

process in which fruits develop without fertilization; they contain no embryos or seeds; this is how we get seedless fruits.