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

Which term describes organisms which live in lake/ocean, Which term is used...

Which term is used to describe organisms that live on or in the bottom of an ocean or lake. Such organisms can be found anywhere from the shoreline to greatest ocean depths? a)

Asymptomatic patient-chronic mitral regurgitation, Asymptomatic patient: ...

Asymptomatic patient: The current opinion is that in asymptomatic patients with left ventricular dysfunction and severe MR surgery should not be delayed. The echo cardiographic a

Explain the metabolic alterations during cancer, Explain the Metabolic Alte...

Explain the Metabolic Alterations during Cancer? As we have studied earlier, patients with advanced cancer experience profound anorexia, early satiety, changes in the structure

Explain the term microfilaments, Explain the term Microfilaments ? Mi...

Explain the term Microfilaments ? Microfilaments are fine fibrils, only 7 nm in diameter, composed of a protein called actin. Actin is one of the two major proteins involved

What are the factors affecting taste quality, Q. What are the factors Affec...

Q. What are the factors Affecting Taste Quality? You may have experienced that the four primary tastes i.e., sweet, sour, salty and bitter are not sensed with an equal ease. Th

Define about traumatic needles, Define about Traumatic needles Traumat...

Define about Traumatic needles Traumatic needles are needles with holes or eyes which are supplied to the hospital separate from their suture thread. The suture must be thread

Reed-swamp stage - hydrarch, Reed-Swamp Stage - Hydrarch This stage is...

Reed-Swamp Stage - Hydrarch This stage is also known as amphibious stage, as the plants of the community are rooted but most parts of their shoots remain exposed to air. Speci

A decrease in parasympathetic discharge to the heart, A decrease in parasym...

A decrease in parasympathetic discharge to the heart leads to A. a decrease in the conductance of F-channels in SA node cells. B. an increase in the conductance of potassium

Define titrimetric method - 2, Define Titrimetric Method - 2, 6 Dichlorophe...

Define Titrimetric Method - 2, 6 Dichlorophenol Indophenol Method? The titrimetric method is a redox titration method which depends on the reduction of the blue dye 2,6 dichlor

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