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

Ozone layer play in the evolution of early life on earth, What role did the...

What role did the appearance of the ozone layer play in the evolution of early life on Earth? Ultraviolet radiation from the sun damages DNA, but the development of the ozone l

Define dietary modifications in the diet of the elderly, Define Dietary mod...

Define Dietary modifications in the diet of the elderly? Loss of teeth due to increased decay of teeth and gums is common in aged person. Fitting dentures may also make chewin

What is the important characteristics of soy protein, The important functio...

The important functional characteristics of soy protein The most important functional characteristics of soy protein concentrates are water-binding (water adsorption) capacity,

Explain the term antioxidants, Normal 0 false false false ...

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4

Define errors of number of sex chromosomes of an individual, What are the m...

What are the main diseases caused by errors of the number of sex chromosomes in the cells of an individual? Diseases caused by the abnormal number of sex chromosomes are called

Phases of respiration in animals, Phases of Respiration in Animals The...

Phases of Respiration in Animals The procedures of respiration in these animals have the following phases. i) External respiration is usually described as breathing. It inv

Explain the invasive species, Explain the Invasive species? Tens of tho...

Explain the Invasive species? Tens of thousands of non-native species have been introduced into the United States of America, with more arriving each year. These species can ha

Spermatogenesis, SPERM A T OGENESIS The process of maturation of ...

SPERM A T OGENESIS The process of maturation of reproductive cells in the testes of male to form spermatozoa (sperm) is known as spermatogenesis. The testes are formed

Which are the plant tissues that form the plant roots, Which are the plant ...

Which are the plant tissues that form the plant roots? The roots have a central portion known as medulla made of vascular tissue (inner xylem and outer phloem). The medulla is

Define the basic types of drying process, Define the Basic Types of Drying ...

Define the Basic Types of Drying Process? Primarily, there are three basic types of drying process: a) Sun drying and solar drying;  b) Atmospheric drying including batch

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