Question

Deficiency symptom of nitrogen and potassium are visible first in
(a) Buds
(b) Roots
(c) Senescent leaves
(d) Young leaves

Answer 1

Hint: Generally nutrient deficiencies are seen when the growth medium has insufficient nutrients or the plants are unable to absorb them. In the case of nitrogen and potassium deficiency, it is first noticed in the main organs for photosynthesis, especially the older ones.

Complete answer:
Nutrient deficiencies in the plants occur when the nutrients are insufficient in the medium or they cannot be absorbed and assimilated efficiently by the plants due to unfavourable environmental conditions. Different deficiencies affect different parts of the plant, and different deficiency symptoms are seen in different locations initially. The deficiency symptoms of Nitrogen and Potassium are characteristically seen in the old and senescent leaves of the plants. This is because plants generally move the nutrients from older parts to the younger leaves and hence deficiency symptoms are seen in senescent leaves first.
The characteristic symptom of nitrogen deficiency is the development of uniform yellowing of the leaves including the veins that are more pronounced on the older leaves. The leaves are stiffened and become erect. Under potassium stress or potassium deficiency, the yellowing of leaves starts from the tips or the margins of the leaves and extends towards the centre of the leaf base. The yellow discolouration later becomes necrotic (seen as dead spots) with leaf curling. This occurs because the plants are unable to make sufficient chlorophyll and start appearing pale green or yellowish.
So, the answer is, “Senescent leaves”

Note:
- The symptoms of nitrogen deficiency are relatively easy to detect in some plant species. The symptoms include retarded plant growth, and yellowing of leaves because of insufficient chlorophyll.
- Plants are also reported to show nitrogen deficiency symptoms in different parts too.
- For example, in the case of tea plants, nitrogen deficiency is identified by a retarded shoot growth and yellowing seen in younger leaves