Heterospory and Origin and Evolution of Seed Habitat in Land Plants – Pteridophytes. Evolutionary Significance of Heterospory and Seed Development in. feature of the seed habit, the enclosure of the female spore; ” Der. Embryosack der s]iorous Pteridophytes there may be little or no difference in the size. Heterospory and seed habit. Reference * Botany for degree students – pteridophyta by:Vasishtha B.R Sinha A.K. Singh V.P *

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By sudden hetdrospory of the temperature, the size of the microspores in the sporocarp of Marsilea increases by six times.

The differentiation of microspores and megaspores and their dependence upon the sporophyte has certain advantages. However, in megasporangium, a part of the sporogenous tissue degenerates they provide nutrition to growing sporocytes megaspores.

Experimental studies on Selaginella Goebel, and Marsilea Shattuck, suggest that nutritional factors mainly govern the heterospory. Of the four, only one is retained ensuring enough space, food and greater chance of developing into a healthy female gametophyte. The condition of Heterospory in Selaginella constitute one of the most important phases in the evolution of the plants.

These species were C. The phenomenon of Heterospory is of great biological advantage because of the fact hetetospory a large megaspore which contains female gametophyte derives its food from the sporophyte, and is independent of the external conditions as might interfere with the growth of a free living gametophyte.

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

This reduced the chance of genetic variability among homosporous plants. Megaspores are comparatively large spores produced in limited numbers 1 to 4 inside the megasporangium. Though Selaginella as well as lower Spermatophytes shows homologies in their structure as follows: Development of organic connection between the megasporangial wall and the megaspores.


Difference between Microspores and Megaspores: This reduces the chance of self-fertilization and increases the chance of variability in the progenies.

Developments for the availability of sufficient nutrition. Heterospory and Seed habit in Pteridophytes Ferns. They are female spores which on germination produce the female gametophyte. Heterospory is the production of two or more types of spores. In Selaginella, there is remarkable approach to the seed habit, on account of the following important features:. What heyerospory the possible evolutionary events in the formation of seeds in land plants?

Permanent retention of megaspore within the megasporangium. It is the greatest adaptation of land plants to ensure its reproductive success and pteridophytees. Difference between Microspores and Megaspores.

Heterospory and Seed habit in Pteridophytes (Ferns) | Plant Science 4 U

Thus, the heterosporous condition is considered as precondition for the seed habitat. Development of seed with protective layers. In certain spaces of Selaginella only one megaspore develops within the megasporangium.

Learning and Loving Plants. Here’s how it works: Evolution of the seed is one of the most crucial adaptations in Phanerogams for successful survival in terrestrial habitat.

Heterospory and Seed Habit in Pteridophytes | Botany

Land plants up to pteridophytes are homosporous. Here one thing may be noticed that the microspores develop male gametophytes whereas the megaspores the megaspores germinate into the female gametophytes which may also be called as microgametophytes and megagametophytes.

This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. Some of these forms even arrived at the seed stage. Types of Stelar Amd and its Evolution in Pteridophytes. It thus forms haibt starting point for the new embryo, than an independent green prothallus which has to manufacture its own food. In homosporous plants, the male and female gametes are formed in the same prothallus. Seeds have many advantages than spores: Leave a Reply Click here to cancel reply.


It becomes quite evident that Selaginella has considerably advanced towards the seed habit in a few species, but its approach to the true seed is not complete due to the following features:.

Heterospory and Seed Habit in Pteridophytes | Botany

The indication of the starting of pollination mechanism is observed in Selaginella where a temporary retention of the female gametangia within the megasporanigum is evident. Rounded red circles indicates different steps. Step 5, 6, 7, 8: What is Vegetative Propagation? The exosporic gametophytes have to find the nutrients from the external environment.

In angiosperms, it is retained. Thus the chance of fertilizing an pterdiophytes with the sperm of the same prothallus is very high. You may also like…. Microspores are smaller in size and develop into the male gametophyte while the megaspores are large and develop into female gametophyte.