Which one of the following roles is not characteristic of an essential element?

Which one of the following statements can best explain the term critical concentration of an essential element?

Deficiency symptoms of an element tend to appear first in young leaves. It indicates that the element is relatively immobile. Which one of the following elemental deficiency would show such symptoms?

1.  Sulphur

2.  Magnesium

3.  Nitrogen

4.  Potassium

Which one of the following symptoms is not due to manganese toxicity in plants?

Reactions carried out by N₂ fixing microbes include

(i) $2{\mathrm{NH}}_3$ $+$ $3{\mathrm{O}}_2$ $\to$ $2{\mathrm{NO}}_2^{-}$ $+$ $2{\mathrm{H}}^{+}$ $+$ $2{\mathrm{H}}_2\mathrm{O}$

(ii) $2{\mathrm{NO}}_2$ $+$ ${\mathrm{O}}_2$ $\to$ $2{\mathrm{NO}}_3$

Which of the following statements about these equations is not true?

With regard to the biological nitrogen fixation by Rhizobium in association with soyabean, which one of the following statement/ statements does not hold true.

Match the element with its associated functions/roles and choose the correct option among given below:

Codes

1.  1, 2, 3, 4, 5

2.  4, 1, 3, 2, 5

3.  3, 2, 4, 5, 1

4.  2, 3, 5, 1, 4

Plants can be grown in

1.  soil with essential nutrients.

2.  water with essential nutrients.

3.  either water or soil with essential nutrients.

4.  water or soil without essential nutrients.

Which metal ion is a constituent of chlorophyll ? 

1. Iron 

2. Copper

3. Magnesium 

4. Zinc