BORON 

Boron is absorbed by plants as boric acid (H₃ BO₃ ). 

Functions of boron: 

1. Boron is responsible for cell wall formation and stabilization, lignification and xylem differentiation. 

2. It plays an important role in pollen germination and pollen tube growth. 

3. It imparts drought tolerance. 

4. It facilitates transport of potassium in guard cells and also aids in stomatal opening. 

5. Nodule formation in legumes 

Deficiency symptoms of Boron: 

1. Deficiency Symptoms are observed on the terminal buds or youngest leaves. 

2. Flowering and fruit development are restricted. 

3. Sterility and mal formation of reproductive organs. 

4. Thickened and curled leaves.

5. Discoloration, cracking or rotting of fruit, tubers or roots 

6. Internodes become shorter and give a rosette appearance. 

7. Boron deficiency symptoms occur as internal cork of apple, top sickness of tobacco, heart rot of sugarbeet, etc. 

MOLYBDENUM 

Molybdenum is absorbed by plants as molybdate (MoO₄). 

Functions of Mo: 

1. Biological nitrogen fixation is catalyzed by the molybdenum containing enzyme nitrogenase. 

2. Nitrate is reduced by the nitrate reductase enzyme present in the cytoplasm by the transfer of electrons from molybdenum to nitrate 

3. It affects the formation of pollens, viability of pollens and development of anthers. 

4. It is involved in the protein synthesis. 

Deficiency symptoms of Mo: 

1. Flower formation is inhibited. 

2. Chlorotic mottlings between the veins on old or middle leaves. 

3. Reduce activity of symbiotic and non-symbiotic N fixation. 

4. In case of cauliflower, molybdenum deficiency symptom is called as whip tail.