Biology Ch#09-Lecture#12 Evolution of seed (F.Sc 1st Year)
Автор: BISM Academy
Загружено: 2019-11-01
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Описание:
EVOLUTION OF SEED. A review of the kingdom plantea indicates that the seed-plants (spermatophytes) predominate over non-seed vascular plants. History. One of the most significant events in the history of land plants was the development of seed habit. It was an important change in the reproductive system of the vascular plants which occurred approximately 390 million years ago. First complete seeds appeared approximately 365 million years ago during late Devonian times. SEED. A seed may be defined as a fertilized ovule. Ovule. An ovule is an integumented indehiscent megasporangium. Integuments are specialized protective coverings around megasporangium which vary in number. Spermatophytes. All seed producing plants are called spermatophytes. Various steps involved in the evolution of seed habit are as follows.
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