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.

(A-D) True.
$(b)$ False. Not all mineral elements present in a cell are essential for the cell. For example,plants growing near radioactive mining sites accumulate radioactive elements,which are not essential for their growth.
$(c)$ False. Nitrogen is highly mobile in plants. It is readily mobilized from older,senescing parts to younger,developing parts.
$(d)$ False. It is very difficult to establish the essentiality of micronutrients because they are required in extremely small (trace) quantities,making it challenging to create a nutrient medium completely free of these elements.