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

Bacterial growth medium, how a simple medium can be converted into selecti...

how a simple medium can be converted into selective differential and enriched medium?

Define food processing unit operations, Define Food processing unit operati...

Define Food processing unit operations? Food processing unit operations are involved in the engineering aspects of food processing, packaging and storage. Heating, cooling, dry

Explain the peripheral nervous system in detail, Explain The Peripheral Ner...

Explain The Peripheral Nervous System in detail? The peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system. The somatic nervous

Causes of solid wastes, The main causes for the rapid growth in the quantit...

The main causes for the rapid growth in the quantity of solid wastes are- (i)     Over population: the ever increasing population is increasing all types of pollution; same is t

Dna primer, what is the function of dna primer

what is the function of dna primer

What happens within the cell in the third interface period, What are the ev...

What are the events that mark the beginning and the end of the third interphase period? What happens in the cell in this period? The third interphase period is the G2. It star

Agro industrial-complete feed blocks, Complete feed blocks For manufac...

Complete feed blocks For manufacturing the pellets, processes such as grinding, mixing, steaming and pressing and some times extruding, are applied using special and expensive

Enterocoelous pattern – coelom, Enterocoelous pattern – Coelom In ent...

Enterocoelous pattern – Coelom In enterocoelous development of coelom the mesoderm arises in the embryo as paired lateral pouches growing out from the archenteron. The pouche

Mycroboilogy mycoplasma, How we write assimgment about mycobiology of mycop...

How we write assimgment about mycobiology of mycoplasma in detail

Define prognosis of eating disorders, Define Prognosis of Eating Disorders?...

Define Prognosis of Eating Disorders? About 50% of the patients recover fully from anorexia nervosa and achieve normal weight, 30% improve but have a partial recovery and 20% 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