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

What do you understand by pericardium, Q. What do you understand by Pericar...

Q. What do you understand by Pericardium? Pericardium is the covering sac of the heart. The pericardium prevents acute cardiac chamber dilatation. Acute pericarditis, pericardi

Define advantages of using the plate counts method, Define Advantages of Us...

Define Advantages of Using the Plate Counts Method? 1. It is simple and sensitive method. 2. It provides viable count as only live cells will grow and produce the colony.

Write the meaning of hypoglycemia, Q. Write the meaning of Hypoglycemia? ...

Q. Write the meaning of Hypoglycemia? Hypoglycemia is a Greek term: hypo -meaning less; glyc - means sweet; and emia - means "of the blood". It is a condition in which less th

Sources of stem cells-pulp tissue revascularization, A) General:   u...

A) General:   umbilical cord  Placenta  Bone marrow  Ophthalmic cornea { conjectiva of the eye }  Kidney  Spleen  (B) Dental:  Dental pulp

Explain coronaw artery disease, Explain CORONAW ARTERY DISEASE (CAD)? A...

Explain CORONAW ARTERY DISEASE (CAD)? As far as CAD is concerned the people of South Asian region are at a very disadvantageous position. The term 'South Asians' includes perso

Explain risk factor global perspective in heart dieases, Explain risk facto...

Explain risk factor at the global perspective in heart diease? While the risk of Cardio-vascular diseases has been found to be variable in different ethnic groups with the high

Which of following is not true regarding the immune response, Which of the ...

Which of the following is not true regarding the immune response? Answer The immune response uses chemical and phagocytic cells to destroy foreign cells. Once initiated, the immune

Define surgery, Define Surgery? Surgery ! Does the word itself not crea...

Define Surgery? Surgery ! Does the word itself not create a feeling of anxiety and bring our thoughts towards a debilitating state of health which would be accompanied by pain,

Giardia – flagellates, Giardia – Flagellates Giardia intestinalis inha...

Giardia – Flagellates Giardia intestinalis inhabits the intestine of man. It has the distinction of being probably the first parasitic protozoan to be seen by Antony Van Leeuw

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