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

Which are the organs of the excretory system, Q. Which are the organs of th...

Q. Which are the organs of the excretory system? The excretory system is formed of ureters (two), kidneys (two), bladder and urethra.

Active Transport, How does the addition of a watery secretion to the conten...

How does the addition of a watery secretion to the contents of the gut help in the process of digestion?

What is the function of the umbilical cord, What is the function of the umb...

What is the function of the umbilical cord? The umbilical cord haves blood vessels which convey blood among the fetus and the placenta.

Explain the uses of isP in infant formulas, Explain the Uses of ISP in Infa...

Explain the Uses of ISP in Infant formulas Infant formulas  Infant formulas, where milk solids have been changed by soy products, are well established commercial products

Plant responses., Why do climbers such beans plants coil up a post?

Why do climbers such beans plants coil up a post?

Studying life histories of insects, Studying life histories of insects ...

Studying life histories of insects Cut large rectangular holes in the sides of a big cardboard container and cover them with muslin folded over at the edges and gummed or paste

Investigations process of acute pericarditis, Q. Investigations process of ...

Q. Investigations process of acute pericarditis? 1) Blood Examination Erythrocyte sedementaion rate (ESR) may be elevated in tuberculous; collagen and purulent pericarditis.

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