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Plant Growth and Development

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Class 10 Class 12
Why is abscisic acid also known as stress hormone ?

Abscisic acid is known as the stress hormone because of the following reasons :

1. It helps plant to cope with adverse environmental conditions or stresses.

2. It causes temporary closure of stomata due to which there is reduction in the rate of transpiration. Therefore, it acts as antitranspirant and reduces water loss.

3. It acts as a general growth inhibtor and inhibitor of plant metabolism

4. It inhibits seed germination.

5. It induces dormancy to escape the unfavourable conditions.

What is C/N ratio ?

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

Who coined the term gibberellin ?

Yabuta.

Term kinetinwas coined by whom ?

Skoog and Miller.

Who isolated auxin and from where ?

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

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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