The criteria for essentiality of an element for a plant include all except:
1. It must be absolutely necessary for supporting normal growth and reproduction
2. The requirement must be specific and not replaceable by another element
3. It must be directly involved in the metabolism of the plant.
4. They must be present in the plants in a concentration in excess of 10 mmole/Kg of dry matter.

Which one of the following is not a nitrogen-fixing organism?

1. Anabaena

2. Nostoc

3. Azotobacter

4. Pseudomonas

How many ATP molecules are required to biologically fix one molecule of nitrogen into two molecules of ammonia?
1. 4
2. 8
3. 12
4. 16

When the plants are grown in magnesium deficient but urea rich soil, the symptoms expressed are:
1. yellowish leaves
2. colourless petiole
3. dark green leaves
4. shoot apex die.

Select the mismatch.

(1) Frankia                      Alnus

(2) Rhodospirillium            Mycorrhiza

(3) Anabaena                   Nitrogen fixer

(4) Rhizobium                 Alfa-fa

Which is essential for the growth of root tip?
(1) Zn

(2) Fe

(3) Ca

(4) Mn

The oxygen evolved during photosynthesis comes from water molecules. Which one of the following pairs of elements involved in this reaction?

1. Manganese and chlorine

2. Manganese and potassium

3. Manganese and molybdenum

4. Magnesium and chlorine

Minerals known to be required in large amounts for plant growth include

1. Phosphorus, potassium, sulphur, calcium

2. calcium, magnesium, manganese, copper

3. potassium, phosphorus, selenium, boron

4. magnessium, sulphur, iron, zinc

Deficiency symptoms of nitrogen and potassium are visible first in

1. senescent leaves

2. young leaves

3. roots

4. buds

The most abundant intracellular cation is

1. Na⁺

2. Ca²⁺

3. H⁺

4. K⁺