Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
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.
The principal nitrogenous excretory compound in humans is synthesised: 1. in kidneys but eliminated mostly through liver 2. in kidneys as well as eliminated by kidneys 3.
What is the RQ if glucose was the only source of fuel used in metabolism?
Q. Define characteristic of Doppler Echocardiographic? Ans. Doppler findings of cardiac tarnponade are based on the following characteristic respiratory variations in intr
Define effect of Fat on quality and quantity of human milk? Fat content of milk appears to be subject to variability as compared to other constituents. The average fat content
What is plant coleoptile? Why does the removal of the coleoptile extremity disallow plant growth? Coleoptile is first (one or more) aerial structure of the sprouting plant that
Which one of the following statements is correct with respect to AIDS? 1. The HIV can be transmitted through eating food together with an infected person 2. Drug addicts are
Explain about Battery Battery: Two electrodes (zinc and carbon) placed in electrolyte (dilute sulfuric acid). Chemical reactions in electrolyte force positive charges to
How are the main classes of arthropods classified according to the presence of larval stage in their embryonic development? In crustaceans there are species with direct and oth
SODIUM The element is available in table salt. A proper balance of sodium and potassium is essential. Its absorption is under control of aldasterone. The various f
Asymmetrical and Spherical - Metazoa Some creatures are asymmetrical: no matter which way we try to divide them through the middle, no two halves would appear alike. In simple
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!
whatsapp: +1-415-670-9521
Phone: +1-415-670-9521
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd