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 about the autodispensor, Explain about the Autodispensor? This ...

Explain about the Autodispensor? This is used to transfer accurate quantities of liquids that are difficult to pipette like concentrated acids, alkalis, etc. You will also use

Phylogeny and Evolution, While studying evolution, a student comes across a...

While studying evolution, a student comes across a cladogram that includes clades like amphibia, reptilia, aves, and mammalia. What must be the basal clade?

Give an example of structural protein, Give an example of each of the follo...

Give an example of each of the following types of proteins: a. Enzyme b. Structural protein c. Motor protein

Biological diversity of an ecosystem, Q. Is monoculture a system that contr...

Q. Is monoculture a system that contributes to great biological diversity of an ecosystem? The Monoculture implies that in a large area a single crop (only one species of plant

Objectives of dietary management of myocardial infarction, Q. Objectives of...

Q. Objectives of dietary management of myocardial infarction? The objectives of dietary management of myocardial infarction patients are as follows: - To provide rest to the

Explain fungal infections, Fungal Infections Intravenous infusion of am...

Fungal Infections Intravenous infusion of amphotericin B deoxycholate  frequently causes fever and chills, and sometimes headache, nausea, vomiting, hypotension and tachypnea,

Homeopathic cures, If water dousing, homeopathic cures, and so on work for ...

If water dousing, homeopathic cures, and so on work for just me but not for anyone else, it is still science.

Explain about rna molecules, Explain how early RNA molecules might have bee...

Explain how early RNA molecules might have been able to respond to natural selection. Every RNA molecule might have competed with slightly dissimilar RNA molecules for nucleoti

Molybdenum and vanadium, Molybdenum and Vanadium - Inorganic Nitrogen and S...

Molybdenum and Vanadium - Inorganic Nitrogen and Sulphur Metabolism Molybdenum must be available in nature in order to meet the demand of Mo for the formation of nitrogenase n

Do protozoans have a cellular nucleus, Q. Do protozoans have a cellular nuc...

Q. Do protozoans have a cellular nucleus? All protozoans, as eukaryotes have nucleus, some species like the paramecium have two nuclei the micronucleus and the macronucleus.

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