Chapter 38

Epicotyl

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

Hypocotyl

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

Anther

In an angiosperm, the terminal pollen sac of a stamen, where pollen grains with male gametes form

Ovary

In flowers, the portion of a carpel in which the egg-containing ovules develop (becomes fruit that encloses seed)

Aggregate Fruit

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

Multiple Fruit

A fruit derived from an inflorescence, a group of flowers tightly clustered together

Fruit

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

Fragmentation

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

Double Fertilization

A mechanism of fertilization in angiosperms, in which two sperm cells unite with two cells in the embryo sac to form the zygote and endosperm

Male Gametophyte

A microspore undergoes mitosis and cytokinesis, producing two separate cells called the generative cell and tube cell; together, these two cells and the spore wall constitute a pollen grain, which at this stage of its development is an immature male gametophyte; the spore wall usually exhibits an elaborate pattern unique to the particular plant species

Sepal

A modified leaf in angiosperms that helps enclose and protect a flower bud before it opens

Petal

A modified leaf of a flowering plant; the often colorful parts of a flower that advertise it to insects and other pollinators

Endosperm

A nutrient-rich tissue formed by the union of a sperm cell with two polar nuclei during double fertilization, which provides nourishment to the developing embryo in angiosperm seeds; chromosome number = triploid

Pistil

A single carpel or a group of fused carpels

Scutellum

A specialized type of cotyledon found in the grass family

Megaspore

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

Microspore

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

Ovule

A structure that develops within the ovary of a seed plant and contains the female gametophyte (each becomes a seed)

Seed Coat

A tough outer covering of a seed, formed from the outer coat of an ovule; in a flowering plant, the seed coat encloses and protects the embryo and endosperm

Asexual Reproduction

A type of reproduction involving only one parent that produces genetically identical offspring by budding or by the division of a single cell or the entire organism into two or more parts

Radicle

An embryonic root of a plant; the first organ to emerge from the germinating seed

Vegetative Reproduction

Cloning of plants by asexual means

Coleorhiza

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

Coleoptile

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

Carpel

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

Stamen

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

Style

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

Stigma

The sticky part of a flower's carpel, which traps pollen grains

Pollination

The transfer of pollen from anther to stigma - the first step in a chain of events that can lead to fertilization; if a pollen grain germinates, a pollen tube grows down the style toward the ovary

Imbibition

The uptake of water due to the low water potential of the dry seed

Maintain Seed Dormancy

1. Exclusion of water or oxygen by impermeable seed coat 2. mechanical restraint of embryo by tough seed coat 3. chemical inhibition of embryo development

Dormancy

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

Simple Fruits

A fruit derived from a single carpel or several fused carpels

Generative Cell/Tube Cell

During maturation of the male gametophyte, the generative cell passes into the tube cell; the tube cell now has a completely free-standing cell inside it and produces the pollen tube (a structure essential for sperm delivery to the egg); during elongation of the pollen tube, the generative cell usually divides and produces two sperm cells, which remain inside the tube cell; the pollen tube grows through the long style of the carpel and into the ovary, where it then releases the sperm cells in the vicinity of an embryo sac

Pollen Grain

Made up of a generative cell, tube cell, and spore wall

Apomixis

The asexual production of seeds

Receptacle

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

Eudicot/Monocot

Two cotyledons/one cotyledon

Modes of Pollination

Wind, bees, moths, bats, birds

Dispersal

Wind, water, and animals

Microsporangia

Within the microsporangia (pollen sacs) of an anther are many diploid cells called microsporocytes (aka microspore mother cells); each microsporocyte undergoes meiosis, forming four haploid microspores, each of which can eventually give rise to a haploid male gametophyte