Question

Boron regulates
(A).Ribosomal fraction
(B).Translocation of sugars
(C).Carbohydrate metabolism
(D).Calcium metabolism
Choose the correct answer from the options given below:

• A. (A), (B) and (C) only.
• B. (A), (B) and (D) only.
• C. (A), (B), (C) and (D).
• D. (B), (C) and (D) only.

Hint:

Boron is highly immobile in most plants.
Because it is essential for cell wall synthesis and sugar translocation, deficiency symptoms always appear first at the growing tips (meristems) of the plant.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Boron (B) is an essential micronutrient for plants.
Unlike most other micronutrients, which function primarily as enzyme cofactors, boron plays a key role in cell wall structure and metabolic regulation.

Step 2: Detailed Explanation:
Let us analyze the physiological processes regulated by boron:
- (A) Ribosomal fraction: Boron is essential for nucleic acid synthesis and the stability of the ribosomal fraction.
Under boron deficiency, RNA synthesis decreases rapidly, leading to a decline in protein synthesis. Thus, (A) is correct.
- (B) Translocation of sugars: This is one of the most well-known functions of boron.
Borate ions react with sugars (like sucrose) to form cis-diol borate complexes.
These uncharged complexes pass through highly hydrophobic cell membranes much more easily than polar sugar molecules, facilitating sugar transport from leaves to growing sinks. Thus, (B) is correct.
- (C) Carbohydrate metabolism: Boron regulates the activity of several enzymes in carbohydrate pathways.
Deficiency leads to the accumulation of starch and sugars in leaves and impairs the synthesis of structural carbohydrates. Thus, (C) is correct.
- (D) Calcium metabolism: Boron and calcium interact closely in cell wall development.
Boron cross-links rhamnogalacturonan II (RG-II) pectins in the cell wall, which requires calcium to stabilize the structure.
Boron deficiency impairs calcium utilization, disrupting cell wall integrity. Thus, (D) is correct.
Therefore, boron regulates all four of these physiological processes.

Step 3: Final Answer:
The correct combination is (A), (B), (C), and (D).