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.

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.

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
Digestion of various disaccharides of the diet The enzymes from brush border membrane of small intestine complete the digestion of various disaccharides of the diet and the pro

Carpentier -Edwards Valve (C-E) :  This is porcine aortic valve preserved in gluteraldehyde and mounted on flexible stent made of cobalt-chromium-nickel alloy (ELGILOY). Glut


Why is pattern baldness more common in men than in women? Pattern baldness is handled by the allele B. Testosterone interacts with the heterozygous genotype (BB′) to make baldn

What is Class Gastropoda in animal kingdom? Snails and slugs are referred to as gastropods because of their characteristic body plan. "Gastro" is derived from the Greek word fo

Define the Assessment of Copper Status in Humans? A reliable index to assess marginal copper status is currently not available. However, severe copper deficiency may be detecte

Define Vitamins and Minerals needs in Nutrient Requirement and Dietary Management Although the exact requirements are not known, it is generally recommended to give plenty of f

Q. How are amino acids brought to the cellular site where translation takes place? What is an anticodon? Amino acids are brought to ribosomes by RNA molecules known as transfer

People with Type 1 DM produce no insulin. People with Type 2 DM do not always produce enough insulin. Insulin is used medically to treat some forms of diabetes mellitus. Patients w

Results: Largely depends on the LV function. In most centres surgical mortality is 3 to 4 percent. For patients with severe LV dysfunction the immediate and late results of sur