Although more than one archegonium may be fertilized, only one gives rise to a viable embryo.
During the latter’s development, part of the prothallus is broken down and used.
In the orchids and in some other plants with minute seeds that contain no reserve materials, endosperm formation is completely suppressed.In other cases it is greatly reduced, but the reserve materials are present elsewhere—e.g., in the cotyledons, or seed leaves, of the embryo, as in beans, lettuce, and peanuts, or in a tissue derived from the nucellus, the perisperm, as in coffee.Other useful products provided by seeds are abundant.Oils for cooking, margarine production, painting, and lubrication are available from the seeds of flax, rape, cotton, soybean, poppy, castor bean, coconut, sesame, safflower, sunflower, and various cereal grains.The pollen tube ultimately penetrates the neck of one of the archegonia.
Not until the second growing season, however, does the nucleus of one of the male cells in the tube unite with the oosphere nucleus.
Frequently small in size and making negligible demands upon their environment, seeds are eminently suited to perform a wide variety of functions the relationships of which are not always obvious: multiplication, perennation (surviving seasons of stress such as winter), dormancy (a state of arrested development), and dispersal.
Pollination and the “seed habit” are considered the most important factors responsible for the overwhelming evolutionary success of the flowering plants, which number more than 300,000 species.nutrient material that gives the new generation an excellent growing start and the seed’s multicellular structure.
Herbaceous nontropical flowering plants usually have seeds weighing in the range of about 0.0001 to 0.01 gram.
Within a given family (e.g., the pea family, Fabaceae), seed size may vary greatly; in others it is consistently large or small, justifying the recognition of “megaspermous” families (e.g., beech, nutmeg, palm, and soursop families) and “microspermous” ones (e.g., milkweed, daisy, heather, nettle, and willow families).
The zygote undergoes a limited number of divisions and gives rise to an embryo.