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Plant Growth and Development

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
Write a note on Growth curve.

Growth curve is the graphical representation of growth against time, thus it is also called sigmoid curve.

A typical S-shaped grand period of growth curve

It has three phases :

(1) Lag phase: It is in the beginning of the growth and represents the time in which minimum growth occurs. The growth is very slow in this phase.

(2) Log/Exponential phase : It represents the phase of maximum growth. If log phase persists for longer time then growth is linear.  Both the progeny cells following mitotic cell division retain the ability to divide and continue to do so.

(3) Stationary phase : It is the phase in which no growth occurs. The limited nutrient supply, the growth slows down leading to a stationary phase.

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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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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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Term kinetinwas coined by whom ?

Skoog and Miller.
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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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