Premature leaf fall is due to a deficiency of

The correct option is D

Phosphorus.

.The correct option is D.

Explanation of correct option:

1. Phosphorus is a necessary macronutrient.
2. Nucleotide, nucleic acid, phospholipid, and other biomolecule biosynthesis are critical.
3. Poor blooms, dull green leaves, red anthocyanin spots, and premature leaf fall, occur due to lack of phosphorus.
4. Another symptom is delayed seed germination.
5. The plant absorbs phosphorus in the form of phosphate ions.
6. Cell membranes, ATP, nucleic acids, phospholipids, and some coenzymes contain it all.

Explanation of incorrect option:

Option A:

1. Zinc is an important and necessary micronutrient.
2. Zinc is required for the activity of carbonic anhydrase and the biosynthesis of auxin.
3. Certain carboxylases and dehydrogenases are also activated by zinc.
4. It has also been reported that zinc deficiency causes auxin degradation.

Option B:

1. Sodium is a micronutrient.
2. It is used in small amounts in plants.
3. It helps in plant metabolism and chlorophyll synthesis.

Option C:

1. Potassium is a macro nutrient.
2. It is required for plant growth and metabolism.
3. It is taken up in the form of the ions K⁺.
4. It is required in greater abundance in meristematic tissue.

Final answer: Premature leaf fall is due to a deficiency of phosphorus.