Phototropism - root and shoot morphogenesis, Biology

Assignment Help:

Phototropism - Root and Shoot Morphogenesis

 Paratonic growth movement of part of a plant in response to light, e.g. bending of stems of indoor plants towards a window, brought about by increased elongation of cells in growth region at tip of stem on shaded side. Coleoptiles of dark grown Avena seedlings bend towards light, when we provide unilateral light. The tip is found to be playing a role. Actually the tip is site of auxin production. If the tip is removed there is no response to unilateral light. But an agar block containing auxins can substitute for the tip and coleoptile would bend towards the light as if it had not been decapitated. The coleoptile bends towards light because of unequal elongation of cells on two sides. The cells on the darker side elongate faster than those cells on two sides exposed to light.

Generally accepted that effect is due to greater concentration of auxin on dark side than on side facing light but some recent evidence suggests asymmetric distribution of some co-factor that influences auxin effect. Shoots always bend and grow towards light. It is an adaptive mechanism, no doubt. Here, also the auxin is agents that mediate light control just as in coleoptile. One question that needs to be asked is whether the extent of phototropism is proportional to the duration of exposure to light. Secondly, whether the magnitude of curvature is proportional to the energy content of the inducing light.


Related Discussions:- Phototropism - root and shoot morphogenesis

Smack, SMAC K - It is a crud by product of heroin synthesis, commo...

SMAC K - It is a crud by product of heroin synthesis, commonly called brown sugar (Poor man's heroin). The addicts heat the smack powder & inhale its vapour. It is

Two homologous human chromosomes, Two homologous human chromosomes have the...

Two homologous human chromosomes have the following structure: --A--B-.-C--D--E--F--G--H--I--J-- --A--D--C-.-B--E--F--G--J--I--H-- where the letters represent genetic markers and t

Explain the coenzyme in enzyme catalyzed reactions, Explain the Coenzyme in...

Explain the Coenzyme in enzyme catalyzed reactions? Thiamin functions as the coenzyme thiamin pyrophosphate (TPP) in the inetabolism of carbohydrates and branched- chain amino

What is lactation, What is Lactation? High levels of estrogens and prog...

What is Lactation? High levels of estrogens and progesterone during pregnancy stimulate the breasts to develop prior to lactation, or milk production. At the same time, levels

What are the three major types of rna, Q. What are the three major types of...

Q. What are the three major types of RNA? What is meant by heterogeneous RNA? Messenger RNA, or mRNA, transfer RNA, or tRNA, and ribosomal RNA, or rRNA, are the three main type

Water has key participation in organic reactions, Q. Water has key particip...

Q. Water has key participation in organic reactions. What are examples of two types of organic reactions in which water is respectively incorporated or liberated in the products of

What are the types of cell respiration, What are the types of cell respirat...

What are the types of cell respiration? There are two types of cell respiration: aerobic cell respiration, a reaction with participation of molecular oxygen (O2), and anaerobic

Define iron factors affecting absorption of dietary iron, Define Iron Facto...

Define Iron Factors affecting absorption of dietary iron? We have read earlier that iron in foods occurs either as haem or non-haem iron. Haem iron comprises of iron in combina

Leaf, Which one of the following is an example of a tree having simple leaf...

Which one of the following is an example of a tree having simple leaf ? 1. Neem 2. Rose 3. Mimosa pudica 4, Peepal.

Determine the final cell volume, Find the initial osmotic pressure at room ...

Find the initial osmotic pressure at room temperature for a cell if the only ions present are KCl and NaCl on either side of the membrane. Assume the concentrations for K+ and Na+

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