Seed coat effects, Biology

Assignment Help:

Seed Coat Effects

In some seeds dormancy is imposed by the presence of the seed coat; if this is removed, the seed germinates. Two possible types of mechanisms could be involved, one biochemical or physiological and the other purely mechanical.

Scarification

The seed coat is nearly impervious to the diffusion of gases. Wareing's group found that seeds of Birch (Betula Pubescens), which would not germinate intact, would do so if the seed coat were scratched or broken. Moreover, added oxygen greatly stimulated germination of such damaged seeds. Evidently the embryos themselves were not dormant; they would germinate if isolated from the seed An alternative possibility is that the seed coat might prevent the leaching out of a diffusible inhibitor. The second, or mechanical alternative has been investigated by Y. Esashi and A.C. Leopold using seeds of Xanthium pennsylvanicum (also called Xanthium strumarium), the cocklebur.

This plant produces two kinds of seeds in each fruit large, non dormant ones and small, dormant ones. The investigators used the specially designed apparatus to show that neither type of seed generates enough force to rupture the testa during imbibitions. During growth, however, the large, non dormant seeds generate sufficient force to break it whereas the smaller dormant seeds do not. This shows, for Xanthium at least, that the long held opinion that the embryo must generate sufficient force during germination to rupture the seed coat is correct. Moreover, it is clear that the forces generated by imbibitions alone are not sufficient. Active growth is also needed.


Related Discussions:- Seed coat effects

Explain the reduction in cancer risk, Explain the Reduction in cancer risk?...

Explain the Reduction in cancer risk? Different cancers, especially colon and breast cancer, has been linked not only to phytates but also to protease inhibitors. In vitro stud

Explain disorders of the gastrointestinal tract, Q. Explain Disorders of th...

Q. Explain Disorders of the gastrointestinal tract? The diseases and disorders of the gastrointestinal (GI) tract. Have you ever suffered from abnormal symptoms of the gastroin

How to compare and contrast acids, Compare and contrast acids and bases in ...

Compare and contrast acids and bases in terms of their H+ ion and OH- ion concentrations.

What is prostaglandins , Prostaglandins and the structurally associated mol...

Prostaglandins and the structurally associated molecules prostacyclins, leukotrienes and thromboxanes, are called as eicosanoids because they having 20 carbon atoms. These hormones

Determine the concept of imitation in the learning process, Determine the c...

Determine the concept of  imitation in the learning process The concept of  imitation in the learning process is also a key developmental concept for infants and young children

Phylum plattyheminthes, what are structural adaptation of flatworm to it''s...

what are structural adaptation of flatworm to it''s enviroment /

Sericulture industry, in sericulture industry do which stages of silkworm w...

in sericulture industry do which stages of silkworm weaver buy? why do they do so?

Mathematical and statistical challenges, Progress on these biological issue...

Progress on these biological issues needs both that more mathematics and statistics be brought to bear on them and that new mathematical and statistical tools be prepared. All the

Nutrient intake during constipation, Q. What about the fluid and other nutr...

Q. What about the fluid and other nutrient intake during constipation? The fluid intake should be at least 2 litres daily. This includes fluid as foods and beverage besides wa

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd