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

Define water as a source of dietary minerals, Define Water as a source of d...

Define Water as a source of dietary minerals? Although water is composed of only oxygen and hydrogen, the water we drink or use in food preparation can contain significant amou

What does the formula dpd = sf - tp mean, What does the formula DPD = SF - ...

What does the formula DPD = SF - TP mean? DPD is the abbreviation of diffusion pressure shortage, SF (suction force) is the vacuolar osmotic pressure and TP is the turgor press

Why d scientists pick hydrogen as the basis for mri scanning, Why d scienti...

Why d scientists pick hydrogen as the basis for MRI scanning? Name of the human body that do not appear in an MRI scan. Explain thermal stratification? How does thermal stratifi

Define effect of protein on quality & quantity of human milk, Define effect...

Define effect of Protein on quality & quantity of human milk? Some studies show that the protein content of milk may be affected by chronic protein under nutrition. In some cas

What is the difference between dna and rna, Concerning their biological fun...

Concerning their biological function what is the difference between DNA and RNA? DNA is the source of information for RNA production (transcription) and therefore for protein s

Define the solar concentration, Define the Solar Concentration? As in ...

Define the Solar Concentration? As in food dehydration, one of the simplest methods of evaporating water is with solar energy. A typical example of this method is production a

What are the possible effects on the fetus, What are the possible effects o...

What are the possible effects on the fetus if, during pregnancy, the mother (a) smokes, (b) catches rubella?   a) Smoking during pregnancy can lead to an underwe

Define procedure for determination of fungal and yeast count, Define Proced...

Define Procedure for Determination of Fungal and Yeast Count? Now carry out the exercise following the steps enumerated herewith: 1. Shake the food sample and aseptically tr

What is the average number of minutes a cell, You have 200 cells and find 1...

You have 200 cells and find 120 in interphase, 57 in prophase, 8 in prometaphase, and 5 in metaphase, 8 in anaphase and 2 in telophase. (None in G0 phase). it takes 18 hours to com

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