Question

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

Answer 1

Hint: This process involves a series of cytological and biochemical changes, which cause degradation of macromolecules and remobilization of nutrients from the part of the plant tissues.

Complete answer: Deficiency symptoms of nitrogen and potassium are visible first in senescent (older) leaves. Due to nitrogen deficiency the symptoms include poor plant growth, and leaves become pale green or yellow because they're unable to form sufficient chlorophyll. Leaves during this state are said to be chlorotic. Due to potassium deficiency, the standard symptoms in plants include brown scorching and curling of leaf tips and chlorosis (yellowing) between leaf veins.
Other symptoms of nitrogen deficiency in plants are its flowering, fruiting, protein and starch contents are reduced. Reduction in protein leads to stunted growth and dormant lateral buds.

Additional information:

Role of Nitrogen:
- Nitrogen is an important element of all the amino acids in plants, which makes the plant proteins important within the growth and development of important plants. - Nitrogen may be a component of macromolecules that forms DNA a genetic material. It helps to carry the genetic code within the plant nucleus. - Chlorophyll gives the plant its green color, nitrogen may be a component in it that aids in enhancing these features. - Nitrogen is important in plant processes like photosynthesis. Thus, plants with enough nitrogen will undergo high rates of photosynthesis.

Role of potassium:
- The main role of potassium is to supply the ionic environment for metabolic processes within the cytosol, and intrinsically functions as a regulator of varied processes including growth regulation. - Plants require potassium ions for protein synthesis and for the opening and shutting of the stomata. - Potassium also functions in other physiological processes like protein synthesis, activation of some enzymes - They maintain the cation and anion balance within the cytosol and vacuole.

So, the correct answer is ‘Senescent leaves’.

Note: When potassium is quickly available within the soil, a plant absorbs it through cell wall channels and stores it in vacuoles. However, when potassium is present at very low concentrations, vacuolar potassium is employed to feed the cytoplasm. Due to nitrogen deficiency, plants look thin, pale and the condition is named general starvation.