Sexual Propagation

-
In nature, sexual propagation begins when water, wind, insects, birds, or small mammals carry pollen randomly between plants (see Pollination). In flowering plants, this transfer of pollen enables the male sex cells, or sperm, of one flower to fertilize the female sex cell, or egg, of a second flower (see Fertilization).

The egg is located at the base of the flower in a structure called an ovule, found within the ovary. Depending on the species, an ovary contains one, several, or many ovules. The ovaries of peach and avocado flowers, for example, have one ovule, while those of watermelon and cantaloupe have many.

As the fertilized egg (or eggs) within the ovule begins to develop into an embryonic plant, it produces a variety of hormones that stimulate the outer wall of the ovule to harden into a seed coat. Other biochemical changes in the ovule produce a starchy substance that will be used as a food supply. In this way, the ovule ripens into a seed—a structure containing an embryonic plant and its food supply surrounded by a seed coat. The ovary, which houses the ovule or ovules, is also stimulated by hormones, which cause its tissues to enlarge into a fruit. The fruit contains the ripened ovules, or seeds.

Comments

Post a Comment

Popular posts from this blog

Monocot and Dicot Seeds

-
Image
Monocotyledons (monocots) and dicotyledons (dicots) make up the two large groups of flowering plants, differentiated by their seed structures. Monocot seeds contain one cotyledon, or embryonic leaf. When these seeds germinate, the cotyledon remains below ground, absorbing nutrients from the endosperm, the starchy food supply in the seed. The coytledon transports these nutrients to the developing seedling. Dicot seeds contain two coytledons, which absorb and store the nutrients from the endosperm before the seed germinates. The cotyledons, thick with stored nutrients, emerge above ground during germination, and then transport the stored nutrients to the developing seedling. For a brief time, the cotyledons also serve as the first photosynthesizing leaves, but they wither and die when the true leaves emerge. related articles: flower flower variations in structure flower sexual reproduction flower pollination and fertilization flowering and the life cycle evolution of flowers angios
Read more

Gymnosperm

-
Image
Gymnosperm (Latin gymn-, “naked”; Greek sperma, “seed”), is a common name for any seed-bearing vascular plant without flowers. There are several types: the cycad , ginkgo , conifer , yew , and gnetophyte. Gymnosperms are woody plants, either shrubs, trees, or, rarely, vines (some gnetophytes). They differ from the other phylum of seed plants, the flowering plants (see Angiosperm ), in that the seeds are not enclosed in carpels but rather are borne upon seed scales arranged in cones. The gymnosperms are the most ancient seed plants; they appear to have arisen from fern ancestors in the Devonian Period. Cycads retain the most primitive characters of the extant seed plants. Gnetophytes are considered from morphological and molecular evidence to share a common ancestry with the flowering plants. Living gymnosperms are distributed worldwide, with a majority, particularly the conifers, in temperate and subarctic regions. Cycads and gnetophytes are mainly tropical to subtropical. There are ab
Read more

Cedar Tree

-
Image
Cedar (tree) is a common name for three or four species of large trees native to mountainous areas of North Africa and Asia. Cedar trees belong to the pine family, the members of which have needlelike leaves and, like all conifers, bear their seeds on scales clustered into cones. They differ from other members of the family in their evergreen four-angled leaves borne on short side-branches. The genus produces fragrant, durable, red-colored wood used in construction and cabinetry. The name cedar is also applied to other conifer trees with fragrant wood (see Cypress ). The well-known white cedar grows in swamps of the eastern United States and reaches a height of 24 m (80 ft). An arborvitae is also called cedar; western cedar and eastern white cedar are both important timber trees in the United States. Eastern red cedar, widespread in the eastern United States, is a juniper . A flowering tropical American mahogany is known as Spanish or West Indian cedar. Incense Cedar Native to wester
Read more