Phototropism - root and shoot morphogenesis, Biology

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.

Posted Date: 1/24/2013 1:27:26 AM | Location : United States







Related Discussions:- Phototropism - root and shoot morphogenesis, Assignment Help, Ask Question on Phototropism - root and shoot morphogenesis, Get Answer, Expert's Help, Phototropism - root and shoot morphogenesis Discussions

Write discussion on Phototropism - root and shoot morphogenesis
Your posts are moderated
Related Questions
Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Explain Other lipids in biological compound? Other Lipids :  Another important type of lipids are the steroids, with a basic structure consisting of four interconnecting carb

A cellular system has a total of 500 duplex voice channels. The service area is divided into 150 cells. Suggest a three different cluster size (N) values. In each case, determine

State the Designations for Horizons  Of the several horizons, the master horizons are the results of the fundamental soil forming processes, viz. humification, eluviation  and

What is coronary disease? Coronary disease, or coronary insufficiency, is a disease in which there is total or partial obstruction of one or more of the arteries that irrigate

Define Vitamins and Minerals needs in Nutrient Requirement and Dietary Management Although the exact requirements are not known, it is generally recommended to give plenty of f


Define about Skeletal system Skeletal system provides framework to the body; supports the soft tissues; protects delicate organs. The skeletal system is made up of bones an

Q. What are the conditions favouring the outbreak of Staphylococcal food poisoning? • Botulism is caused by the bacteria Clostridium botulinum. • All low acid foods can s

Q. How is the mesoderm (third germ layer) of triploblastic animals formed? The mesoderm shows from differentiation of endodermal cells that cover the dorsal region of the arche