Fill in the blanks and choose the correct option given below.

(i) promotes senescence and abscission of plant organs especially of leaves and flowers.

(ii) The rise in rate of respiration during ripening of fruits is called as respiratory .

(iii) regulates many physiological processes so it is the one of the most widely sed PGR in agriculture.

(iv) The most widely used compound as source of ethylene is .

(v) Ethephon hastens fruit ripening in tomatoes and apples and accelerates in flowers and fruits.

(vi) is general plant growth inhibitor and an inhibitor of plant metabolism.

(vii) stimulates the closure of stomata in the epidermis and increase the tolerance of plants to various kinds of stresses. It is also called the hormone.

(viii) helps seeds to withstand desiccation and other factors unfavorable for growth. In most situations, it acts as an antagonist to .

(ix) The response of plants to periods of day/night is termed .

(x) The sites of perception of light/dark duration are the in plants.

(xi) The hormonal substances migrates from to apices for inducing flowering only when the plants are exposed to the necessary inductive photoperiod.

(xii) There are plants for which flowering is either quantitatively or qualitatively dependent on exposure to low temperature. This phenomenon is termed