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Plant Growth and Development

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Class 10 Class 12
Write an essay on characteristics of Plant growth regulators. 

Plant growth regulators are small, simple molecules having different compositions. Chemically they may be indole compounds (indole-3-acetic acid, IAA), adenine derivatives like N6- furfrylamino purine, kinetin), derivative of carotenoids (abscisssic acid, ABA), terpenes (giberellic acid, GA3) , gases (ethylene, C2H4). 

They can be divided into two main groups on the basis of the function they perform. 

i. One group is involved in growth promoting activities like cell division, cell enlargement, pattern formation, tropic growth, flowering, fruiting and seed formation etc. For example Auxin, cytokinin, gibberelins etc. 

ii. Hormones in the other group play an important role in plant responses to wounds and stresses of biotic and abiotic origin. They are also involved in various growth inhibiting activities such as dormancy and abscission. For example abscissic acid and ethylene. 

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 Term kinetinwas coined by whom ?

Skoog and Miller.
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Who coined the term gibberellin ?

Yabuta.
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Who isolated auxin and from where ?

Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedling.

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 Give the types of auxins.

Auxins are of two types :

(1) Natural auxins : These are naturally occuring auxins, isolated from plants and are regarded as phytohormones e.g. IAA. NAA etc.

(2) Synthetic auxins : These are synthesized by artificially e.g. IBA 2,4-D etc.

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What is C/N ratio ?

C/N ratio is the ratio of carbohydrates and nitrogenous compounds which regulate the growth in plants. 
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