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.
Q. In sickle cell anemia, a hereditary disease, there is replacement of one amino acid by another in one of the four polypeptide chains of hemoglobin. In this case are all of the s
Connecting implants to natural teeth and use as pier abutments The issue of connecting implants and teeth to support a fixed prosthesis is controversial and unresolved. The inh
Determine the food sources of riboflavin? The food sources of riboflavin include: 1. Rich sources: Liver, dried yeast, egg powder, milk powder. 2. Good sources: Who
Does every amino acid have a central carbon? To which organic group is that central carbon bound? A carboxyl group -COOH, an amine group - NH 2 , an atom of hydrogen -H and a v
In an experiment, it was necessary that you determine the concentration of dsDNA by using a spectrophotometer. You used 6 microliters of your purified dsDNA, and the reading at OD=
Give three ways in which a polar bear is adapted to its environment. A polar bear is adapted to its environment by its high ratio of bulk to surface area, a thick water-repelle
Synthesis of citratefrom acetyl CoA and oxaloacetate: Citrate synthase catalyses this aldol condensation reaction with the release of CoA. There are certain inhibitors to this re
Define regulation of L-PK enzymes by starvation & refeeding? L-PK catalyzes the conversion of phosphoenolpyruvate to pyruvate and plays an important role in directing pyruvate
Entomophily - Cross-pollination It involves insects to carry the pollen to achieve pollination. Salvia exhibits a specialised 'tumapipe' floral mechanism that signifies classi
please give us this phylem''s example...
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: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd