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

Benefit of the double and complete circulation, Q. How many chambers do the...

Q. How many chambers do the mammalian heart and the bird heart have? Concerning temperature maintenance what is the benefit of the double and complete circulation of these animals?

Hearing, HEARIN G  - Sound waves struck ear drum, it starts vibratio...

HEARIN G  - Sound waves struck ear drum, it starts vibrations, these vibrations are carried to MIS → f. ovalis → S. vestibule →  Hellicotrema → S. Tympani → f. rotundus → mi

Blood coagulation factor - circulation, Normal 0 false false ...

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

The prs kit for post removal uses-endodontics principles, The PRS kit is co...

The PRS kit is comprised of          -5 variously sized trephines and corresponding tubes according to material if it's silver or silver point          -A transmetal bur

Cytokinins - plant growth substances, Cytokinins - Plant Growth Substances ...

Cytokinins - Plant Growth Substances Folke Skoog observed that the cell division or differentiation is affected by AMP and other purines. A nucleic acid from yeast was also fo

What will be the most likely explanation, If a lipid bilayer does not form ...

If a lipid bilayer does not form in a test tube of phospholipids in a liquid solvent and instead the heads join together in a circular pattern, the most likely explanation is: a

Define measuring body composition- multiple isotope dilution, Define measur...

Define measuring body composition- Multiple isotope Dilution? Multiple isotope dilution (Total and extracellular body water): It is based on the principle that certain substanc

What is the approximate ph of the salivary secretion, What is the approxima...

What is the approximate pH of the salivary secretion? Is it an acid or basic fluid? What are the main functions of saliva? The saliva pH is approximately 6.8. It is therefore a

Sex-limited traits, can u show the different activities on the topic

can u show the different activities on the topic

Illustrate steps of polymerase chain reaction , There are three steps of PC...

There are three steps of PCR a) Denaturation.  The reaction combination is heated to 95°C for a short time period (about 15-30 sec) to denature the goal DNA into one strands w

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