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 about maple syrup urine disease, Q. Explain about Maple Syrup Urine...

Q. Explain about Maple Syrup Urine Disease? Maple Syrup Urine Disease (MSUD) is a group of inherited metabolic disorders of three branched chain amino acids (BCAA) namely leuci

How do white cells differ from red cells, How do white cells differ from re...

How do white cells differ from red cells (a) In their structure, (b) Their function?   a) White cells have nuclei, red cells do not have nucle

Explain selective and differential culture media, Explain Selective and Dif...

Explain Selective and Differential Culture Media? These are used for isolation of specific organisms. These are designed to isolate a group of closely related organisms and dif

Brain, How brain thinks?

How brain thinks?

Endoplasm and ectoplasm, Normal 0 false false false EN-...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Esophageal obstruction, E s o pha g e a l obstruction It is also...

E s o pha g e a l obstruction It is also known as choke. It may be acute or chronic and is characterized by inability to swallow, regurgitation and bloat. E t

Environment , Environment All organisms are intimately dependent on the ...

Environment All organisms are intimately dependent on the environment from which they derive their sustenance. Organisms from virus to man are obligatorily dependent on the envi

Deficiency diseases, DEFICIENCY DISEASES Animals may suffer from diseases...

DEFICIENCY DISEASES Animals may suffer from diseases caused by deficiencies of energy and proteins, mineral nutrients and vitamins, which generally occur either due to deficiency

Care of records, CARE OF RECORDS Patient's/client's records are unque...

CARE OF RECORDS Patient's/client's records are unquestionably a valuable documents. These should be made on paper of good quality and protected from soiling, and burning. Th

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