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
What are the symptoms and foods associated with campylobacteriosis?  Campylobacteriosis incubation period: 2-5 days after ingestion of contaminated food.  Symptoms: Diarrhoe

Acute and Chronic Tonsilitis: Tonsilitis refers  to the inflammation of  tonsils and lymphatic tissue that are located on each side of oropharynx. Acute infection of  tonsils

Compare and contrast covalent and ionic bonds in molecules, give an example of each.


Q What are the most tremendous known representatives of the platyhelminth phylum? The most popular representatives of the platyhelminthes are worms that cause human diseases, l

Chemical Methods of Estimating Available Nutrients  Water soluble forms of nutrients are available to plants but forms other than water soluble may also become available to pla

Q. What are the substances that are constitute the chromatin? What is the difference between chromosome and chromatin? The chromatin, dispersed in the nucleus, is a set of fila

An increase in blood plasma levels of parathyroid hormone   A. occurs in response to enhance in the levels of calcium ions in blood plasma.   B. leads to enhance in the amou

Signify the term - opercular gill. The gill found in bony fish. Operculum is the outer covering of the gill. When it's drawn away from the body, it pulls water inside the bucca