Chapter 38: Flowering Plant Reproduction and Development
Asexual reproduction does not involve fertilization.
It results in the production of clones-genetically identical copies of the parent plant.
Sexual reproduction is based on meiosis and fertilization.
An individual in the diploid phase of the life cycle is called a sporophyte, while an individual in the haploid phase of the life cycle is called a gametophyte.
It maybe recall that is a type of life cycle, called alternation of generations, has evolved independently in various protists and land plants.
Meiosis occurs in sporophytes and results in the production of haploid spores.
Meiosis and spore production occurs inside structures called sporangia.
Pollination (transfer of pollen grains from an anther to a stigma) occurs, and gametophytes produce sperm (male gametes) and eggs (female gametes) by mitosis.
Fertilization occurs when two gametes fuse to form a diploid zygote.
Sepals are leaflike structures that make up the outermost parts of a flower.
The entire group of sepals in the flower is collectively called the calyx.
Stamens are reproductive structures that produce male gametophytes-also known as pollen grains.
The male gametophytes, in turn, produce sperm that are eventually carried to eggs.
The wall of a pollen grain develops a tough outer coat that includes the watertight compound called sporopollenin.
Self-fertilization, or selfing, occurs when a sperm and an egg from the same individual combine to produce offspring.
In most cases, though, plants outcross-meaning at sperm and an egg from different individuals combine to form offspring.
Outcrossing is the result of cross-pollination-when pollen is carried from the anther of one individual to the stigma of a different individual.
Pollination syndromes are suites of flower characters that are associated with certain types of pollinators.
Germination is a resumption of growth and development.
This step is blocked in many self-incompatible species if the pollen came from the same plant.
When pollen germinates, the tube cell elongates and forms a structure called a pollen tube that grows through the stigma and down the length of the style.
The triploid nucleus resulting from this second fertilization undergoes mitosis and cytokinesis to form the endosperm (“inside-seed”) tissue.
As a seed matures, the embryo and endosperm develop inside the ovule and become surrounded by a covering called a seed coat.
As the fruit matures, the walls of the ovary thicken to form the pericarp, the part of the fruit that surrounds and protects the seed or seeds.
Once they have dispersed from the parent plant, seeds may not germinate for a period of time.
This condition is referred to as dormancy.
Dormancy is usually a feature of seeds from species that inhabit seasonal environments, where for extended periods conditions may be too cold or dry for seedlings to thrive.
The radicle, or embryonic root, emerges first, and it then develops into the mature root system.
This is important because the seedling must have a source of water in order to grow.
Vegetative development produces the nonreproductive portions of the plant body-the roots, leaves, and stems.
As a plant matures, some shoot meristems will produce reproductive structures, a process known as reproductive development.
Embryogenesis is the developmental process by which a single-celled zygote becomes a multicellular embryo.
The first hint of an answer came over 100 years ago when researchers discovered several types of homeotic mutations in flowers of popular garden plants.
Asexual reproduction does not involve fertilization.
It results in the production of clones-genetically identical copies of the parent plant.
Sexual reproduction is based on meiosis and fertilization.
An individual in the diploid phase of the life cycle is called a sporophyte, while an individual in the haploid phase of the life cycle is called a gametophyte.
It maybe recall that is a type of life cycle, called alternation of generations, has evolved independently in various protists and land plants.
Meiosis occurs in sporophytes and results in the production of haploid spores.
Meiosis and spore production occurs inside structures called sporangia.
Pollination (transfer of pollen grains from an anther to a stigma) occurs, and gametophytes produce sperm (male gametes) and eggs (female gametes) by mitosis.
Fertilization occurs when two gametes fuse to form a diploid zygote.
Sepals are leaflike structures that make up the outermost parts of a flower.
The entire group of sepals in the flower is collectively called the calyx.
Stamens are reproductive structures that produce male gametophytes-also known as pollen grains.
The male gametophytes, in turn, produce sperm that are eventually carried to eggs.
The wall of a pollen grain develops a tough outer coat that includes the watertight compound called sporopollenin.
Self-fertilization, or selfing, occurs when a sperm and an egg from the same individual combine to produce offspring.
In most cases, though, plants outcross-meaning at sperm and an egg from different individuals combine to form offspring.
Outcrossing is the result of cross-pollination-when pollen is carried from the anther of one individual to the stigma of a different individual.
Pollination syndromes are suites of flower characters that are associated with certain types of pollinators.
Germination is a resumption of growth and development.
This step is blocked in many self-incompatible species if the pollen came from the same plant.
When pollen germinates, the tube cell elongates and forms a structure called a pollen tube that grows through the stigma and down the length of the style.
The triploid nucleus resulting from this second fertilization undergoes mitosis and cytokinesis to form the endosperm (“inside-seed”) tissue.
As a seed matures, the embryo and endosperm develop inside the ovule and become surrounded by a covering called a seed coat.
As the fruit matures, the walls of the ovary thicken to form the pericarp, the part of the fruit that surrounds and protects the seed or seeds.
Once they have dispersed from the parent plant, seeds may not germinate for a period of time.
This condition is referred to as dormancy.
Dormancy is usually a feature of seeds from species that inhabit seasonal environments, where for extended periods conditions may be too cold or dry for seedlings to thrive.
The radicle, or embryonic root, emerges first, and it then develops into the mature root system.
This is important because the seedling must have a source of water in order to grow.
Vegetative development produces the nonreproductive portions of the plant body-the roots, leaves, and stems.
As a plant matures, some shoot meristems will produce reproductive structures, a process known as reproductive development.
Embryogenesis is the developmental process by which a single-celled zygote becomes a multicellular embryo.
The first hint of an answer came over 100 years ago when researchers discovered several types of homeotic mutations in flowers of popular garden plants.
