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

Osmosis, If you have water, 10% sucrose, and 40% sucrose solution. Which so...

If you have water, 10% sucrose, and 40% sucrose solution. Which solutions were isotonic to each other?

Rhythm and conduction disturbances, Q. Rhythm and conduction disturbances? ...

Q. Rhythm and conduction disturbances? Alterations in cardiac rhythm occur frequently with exercise and are important in understanding a patients function and in providing pred

Differenciate b/w gymnosperms -pteridophytes- bryophytes, How different are...

How different are gymnosperms from pteridophytes and bryophytes? Gymnosperms are not cryptogamic as pteridophytes and bryophytes are. They are phanerogamic and so they form see

Explain the management of renewable resources, Explain the Management of Re...

Explain the Management of Renewable Resources? Since the human population has grown, human impacts on the resources that we use, like fisheries and forests, have continued to g

Why in the preparation of a karyotype analysis, Why in the preparation of a...

Why in the preparation of a karyotype analysis is the use of a substance like colchicine interesting? The Colchicine is a substance that disallows the formation of microtubules

What is triacylglycerol, What is triacylglycerol There are 3 hydroxyl ...

What is triacylglycerol There are 3 hydroxyl groups in a glycerol molecule. If all the three groups are forming ester  linkage with fatty acids, the resulting compound is call

Determine the symptoms of bacillus cereus, Determine the Symptoms of bacill...

Determine the Symptoms of bacillus cereus Extremely large numbers (10 8 per gram) of viable cells of B. cereus must be ingested to develop signs and symptoms of the syndrome.

Scope of user charges, Normal 0 false false false EN-IN...

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

What is the importance of that structure in menstrual cycle, What is the st...

What is the structure into which the follicle is transformed after ovulation? What is the importance of that structure in the menstrual cycle? The follicle that released the ov

Advantage & disadvantage of using algae as source of protein, Define Advant...

Define Advantage & disadvantage of using Algae as source of protein? Advantage Produces proteins which have almost all the Essential Amino acids. Rich in tyrosine

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