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 pregnancy and diabetes mellitus, Explain Pregnancy and Diabetes Mel...

Explain Pregnancy and Diabetes Mellitus? During pregnancy, a woman who has pre-existing chronic disease requires special care, especially in case of mother's suffering from dia

What is blood typing, What is blood typing? Blood typing is the determi...

What is blood typing? Blood typing is the determination, by means of tests, of the categorization of a blood sample concerning blood group systems (specially the ABO system and

Define affluence availability of food as factor for obesity, Define Affluen...

Define Affluence and abundant availability of food as factor for obesity? With increasing affluence, increase in purchasing power and abundance of food, people tend to eat more

Conformational protection - azotobacter, Conformational Protection - Azotob...

Conformational Protection - Azotobacter In conformational protection a Fe-S redox protein provides protection to the enzyme. The protein gets oxidised in the presence of oxyge

Explain the structure and functions of kidney, Explain the Structure and Fu...

Explain the Structure and Functions of Kidney You would have got a clear idea as to where the kidneys are situated. Yes, the kidneys are located in the posterior part of the ab

Define about the anthropometry method, Define about the Anthropometry Metho...

Define about the Anthropometry Method? Anthropometry refers to the measurement of the size and proportions of' the human body. Anthropometric prediction equations estimate body

Main factors that affect the growth of a population, Q. What are the main f...

Q. What are the main factors that affect the growth of a population? The major factors that make populations grow are births and immigration. The major factors that make popula

Explain major role in contributing towards motivation, Major role in contri...

Major role in contributing towards motivation. Psychological factors: Depression, anxiety or phobia induced by illness,  life- style changes or medication effects, may hinder

Define resolution - terminologies used in chromatography, Define Resolution...

Define Resolution - terminologies used in chromatography? Resolution is the effectiveness of the separation and is determined by two factors. These include: Distance

Match each with the corresponding item, Match each item in Column A with th...

Match each item in Column A with the corresponding item in Column B regarding infectious diseases Column A Column B a. Pulmonary tuberculosis i. Enteric infectious protozoan diseas

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