Which of the following statements are true? If false, correct them:
(a) Boron deficiency leads to stout axis.
(b) Every mineral element that is present in a cell is needed by the cell.
(c) Nitrogen as a nutrient element, is highly immobile in the plants.
(d) It is very easy to establish the essentiality of micronutrients because they are required only in trace quantities.

Explanation

Let's analyze each statement step by step to determine their validity and make corrections where necessary.

### Step-by-Step Solution:

1. **Statement (a): Boron deficiency leads to stout axis.**
- **Analysis:** This statement is true. Boron is essential for plant growth and development. A deficiency in boron can lead to various growth abnormalities, including stout or thickened stems (stout axis).
- **Conclusion:** True.

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