RAS question
Which of the following is the PRIMARY macronutrient directly responsible for promoting leafy/vegetative growth in plants?
Correct answer: (B) Nitrogen (N).
Nitrogen is the primary macronutrient that most directly promotes leafy and vegetative growth in plants.
Explanation
Nitrogen is the N in the N-P-K group of major plant nutrients and is linked most directly with green, leafy growth. Nitrogen is a key component of chlorophyll, amino acids and proteins, so a shortage shows up as yellowing of older leaves, or chlorosis. Oregon State University Extension describes nitrogen as the element that promotes rapid green, leafy growth, while distinguishing phosphorus as a nutrient for early root growth and blooming and potassium as a nutrient connected with drought and disease resistance. Nitrogen is both a primary macronutrient and the nutrient most directly tied to vegetative shoot and leaf growth.
Why the other options are wrong
- (A) Phosphorus is a primary macronutrient, but it is associated with early root growth, blooming and seed or fruit formation rather than leafy vegetative growth.
- (C) Potassium is a primary macronutrient, but its role is linked to drought resistance, disease resistance and seed quality, not the primary promotion of leafy shoots.
- (D) Zinc is a micronutrient involved in enzyme systems and auxin synthesis, so it is not the primary macronutrient driving leafy growth.
Concept
Plant-nutrition in basic science requires knowing the distinct roles of N, P and K in fertilisers. RAS agriculture-linked science questions often turn on a precise nutrient-function match rather than a general idea of fertiliser use.