EVOLUTION OF SEED HABIT IN SELAGINELLA PDF

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PDF | Summary The origin of the seed-plant life history, and subsequent should be considered two independent, fundamentally distinct evolutionary problems. Historical biogeography of the ancient lycophyte genus Selaginella: Early. Selaginella largely upon the basis of endosperm development, without regard to great diversities in habit and anatomical details. The association may be. The highest evolved species, i.e., S. apoda has advanced almost upto the In Selaginella, there is remarkable approach to the seed habit, on account of the.

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The evolution of the seed is one of the major events in the history of land plants.

In this paper, we consider the suite of characters that define the seed habit, and discuss the probable selective pressures that produced each character.

Our major conclusion is that most characters are a direct consequence of the origin of heterospory and of natural selection for propagules with larger food reserves. Seeds are traditionally defined by the possession of integuments.

However, some heterosporous pteridophytes possess integument-like structures. Therefore, integuments cannot explain the evolutionary success of seed plants.

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Importance of Heterospory and Seed Habit of Ferns (581 Words)

Rather, we believe that the decisive character in this success is related to pollination. Seed plants differ from other heterosporous lineages in the capture of microspores before dispersal of the ‘megaspore’. This represents an increase in efficiency over Pteridophytic reproduction. Wind-pollination means the propagule is vulnerable to pathogens that mimic pollen, and pathogen pressures may have contributed to some seed characters.

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Importance of Heterospory and Seed Habit of Ferns ( Words)

Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account. Close mobile search navigation Article navigation. Abstract The evolution of the seed is one of the major events in the history of land plants.

Gymnospermsheterosporyintegumentspollinationseed habit. You do not currently have access to this article.

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