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

Explain pancreatitis, Explain Pancreatitis Pancreatitis :- Inflammati...

Explain Pancreatitis Pancreatitis :- Inflammation of the pancreas.

Define nutritional needs during pregnancy, Define Nutritional Needs during ...

Define Nutritional Needs during Pregnancy? It must be evident by now that several physiological changes occur in the body of an expectant mother and that malnutrition can' adve

Xylem transfer cells, Xylem transfer cells The lateral transport of io...

Xylem transfer cells The lateral transport of ions from root xylem to leaves probably takes place via xylem transfer cells which have two special features: The ce

Respiration, different types of animals and their respiratory organ

different types of animals and their respiratory organ

Long-term responses - behaviour of plants, Long-term responses - Behaviour ...

Long-term responses - Behaviour of Plants Plants alter their course of development to suit the prevailing environmental conditions. For example, leaf maturation and fall, onse

What do you mean by nervous system, Q. What do you mean by Nervous System? ...

Q. What do you mean by Nervous System? Structural Organization:   CNS + PNS Functional Organization:   only concerned with PNS Sensory (Afferent) ->  CNS Motor (Effe

Potential disadvantages - digitalis glycosides, Arrhythmias especially in p...

Arrhythmias especially in presence of hypokalemia, lack of mortality benefit. However, their efficacy in reducing the symptoms of heart failure has been established. Digoxin should

Cell determination, Cell Determination Cell determination is a process...

Cell Determination Cell determination is a process through which portions of embryonic genome are selected for expression in particular embryonic cells. Determination to follo

ANIMAL KINGDOM , CLASSIFICATION OF PHYLUM PLATYHELMINTHES..

CLASSIFICATION OF PHYLUM PLATYHELMINTHES..

Can you briefly explain about parasitism, Q. Can you briefly explain about ...

Q. Can you briefly explain about parasitism? The Parasitism is an inharmonious interspecific ecological interaction in which individuals of a species (the parasites) explore or

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