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 is signifying by “gene locus”?, What is signifying by "gene locus"? ...

What is signifying by "gene locus"? The Gene locus (locus means place) is the location of a gene in a chromosome that is the position of the gene in a DNA molecule

Which is the kind of nitrogen waste birds produce, Q Which is the kind of n...

Q Which is the kind of nitrogen waste birds produce? Why does this feature, besides being an adaptation to the terrestrial environment, also mean an adaptation to flight? Birds

Future challenges for scaling from individual to ecosystems, Define Future ...

Define Future challenges for scaling from individual to ecosystems? Scaling of biogeochemical fluxes in terrestrial systems has confirmed much harder. While ecosystem ecologist

What is biomaterial, What is Biomaterial Biomaterial is defined, in the...

What is Biomaterial Biomaterial is defined, in the broader sense, as any pharmacologically inert material that is capable of interacting with a living organism without causing

Define isolated soybean proteins in seafood products, Define isolated soybe...

Define isolated soybean proteins in Seafood products? The most important application in this category is the use of ISP in fish sausage and surimi based restructured fish produ

Restriction endonuclease, Suppose the restriction endonuclease HindIII cuts...

Suppose the restriction endonuclease HindIII cuts a6.0 kb linear piece of DNA into two fragments; an 800 bp fragment and a 5200 bp fragment..... Question: Suppose restriction

Access cavity perforation - types of root perforation, Access Cavity Perfor...

Access Cavity Perforation - Types of Root Perforation Can occur during access cavity perforation (specially in anterior) Due to misdirection of bur during access cavit

Is osmolarity of the interstitial fluid increase or decrease, If the osmola...

If the osmolarity of plasma (inside a capillary) is 300 mOsM, the osmolarity of the tissue fluid (interstial fluid) is 400, and the membranes are permeable to water but not to salt

Animal diversity, why obelia is of special interest in zoology

why obelia is of special interest in zoology

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