21.

Give reasons for the following :

Biofertilisers are preferred over chemical fertilisers.

Give the contributions of the following scientists :

James Langley
Robert Hill
Alexander Fleming
Hugo de Vries

Write the full form of the following :

IUCD

Write the full form of the following :

G-6-PD

Write the full form of the following :

DPD

Give one role and one deficiency symptom of each of the following in plants

(i) Nitrogen (ii) Calcium (iii) Boron

Define :

(i) Photoperiodism
(ii) Double fertilisation

Give the site of secretion and the function of each of the following hormones

(i) Antidiuretic hormone
(ii) Mineralocorticoids
(iii) Relaxin
(iv) Insulin