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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
The role of enthylene is both positive and negative. Justify the statement.

Positive role of ethylene are as follows:

1. Breaking of dormancy : It breaks dormancy of storage organs.

3. Root initiation : In low concentration ethylene helps in root initiation, growth of lateral roots and root hairs.

4. Fruit ripening : It aids in ripening of fruits. C Ethylene is used to induce artificial ripening of these fruits e.g. Citrus, Apple, Mango, Banana etc.

5. Flowering : It stimulates flowering in pineapple and related plants though in other cases the gaseous hormone causes fading of flowers.

Negative role of Ethylene :

1. Growth : It inhibits longitudinal growth and stimulates transverse growth.

2. Senescence : It hastens the senescence of leaves and flowers.

3. Abscission : Abscission of various parts is stimulated by ethylene which induces the formation of hydrolases.

4. Apical dominance : Ethylene promotes apical domiance and prolongs dormancy of lateral buds.


What is C/N ratio ?

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

 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.

 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.

Who coined the term gibberellin ?