Seed coat effects, Biology

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.


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.

Posted Date: 1/24/2013 2:25:05 AM | Location : United States

Related Discussions:- Seed coat effects, Assignment Help, Ask Question on Seed coat effects, Get Answer, Expert's Help, Seed coat effects Discussions

Write discussion on Seed coat effects
Your posts are moderated
Related Questions
Define Larval Stage of Taenia Cystcercus? The pork tapeworn (T: solium) and beef tapeworn (T : saginata , which are endoparasites of humans who are the final hosts

What are twins? Genetically what are the two types of twins that can be generated? Twins are simultaneously generated (within the mother's uterus) offspring. Twins classify acc

As double-stranded DNA is heated a temperature is reached at that the two reaction strands divided.  This procedure is called as denaturation.  The temperature at that half of the

Skeletons of radiolarians The skeletons of radiolarians and foraminiferans form a primary constituent of ocean bottoms where they form 30% or more of the sediment. It is calle

Which of the below terms describes study of animal behavior based on comparisons, observation of patterns, and consideration of environmental adaptations? Is it: a) Ethology (p

What are mutagenic agents? The Mutagenic agents, or mutagens, are physical, chemical or biological factors that can cause alteration in DNA molecules. Instances of believed

Explain about the Macro Minerals? Previously we learnt about the structure, properties, deficiencies/toxicity and recommended dietary intakes of several vitamins. In this unit,

In which chloroplast structure are chlorophyll molecules found? Chlorophyll molecules are placed in an organized manner in order to increase the exposure to light on the thylak

Define the Marasmic Kwashiorkor? In countries where the incidence of protein-calorie malnutrition (PCM) is high, a large number of cases show signs and symptoms of marasmus and

Which of the following serves as an actuating signal, or as part of an actuating signal, in a positive feedback system? A. Blood plasma levels of PTH (Parathryroid Hormone).