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

A decrease in blood plasma levels of calcium, A decrease in blood plasma le...

A decrease in blood plasma levels of calcium will lead to A. an increase in the calcium ion excretion in the urine. B. an increase in the calcium ion absorption from the con

Photosynthesis, explain the role of photophosphorylation and chemiosmosis i...

explain the role of photophosphorylation and chemiosmosis in photosynthesis

Photosynthesis, The neurotransmitter found in insects that is similar to do...

The neurotransmitter found in insects that is similar to dopamine is?

Subphylum trilobitomorpha, Subphylum Trilobitomorpha Subphylum Trilobi...

Subphylum Trilobitomorpha Subphylum Trilobitomorpha involves the trilobites. All species are extinct and the fossils point out that they were all marine forms belonging to Pal

Define the bacillus cereus, Define the Bacillus cereus Bacillus cereus ...

Define the Bacillus cereus Bacillus cereus is not a common cause of food poisoning. It is a Gram positive, aerobic, spore forming rod shaped bacteria normally present in soil,

Cleavage, what are the chemical changes takes place during cleavage

what are the chemical changes takes place during cleavage

Define fat requirements in human body, Define Fat requirements in human bod...

Define Fat requirements in human body? There is no change in fat digestibility at altitude of

Define the methods of concentration, Define the Methods of Concentration? ...

Define the Methods of Concentration? We define the concentration process as one that starts with a liquid product and ends up with a more concentrated, although still liquid a

What is the constitutional unit of proteins, What is the constitutional uni...

What is the constitutional unit of proteins? The constitutional units of proteins are the amino acids. Protein Structure Review - a) Image Diversity b) amino acid stru

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