Gray spots of oat are caused by deficiency of

Which one of  the following is not essential element for plants?

Manganese is required in

Which of the following is a flowering plant with nodules containing filamentous nitrogen-fixing micro-organisms?

A plant requires magnesium for

The association between blue-green algae and fungi occures in :

Which of the following is a free living aerobic non-photosynthetic nitrogen-fixer?

Zinc as a nutrient is used by the plants in the form of :-

Mycorrhiza is a symbiotic relationship between roots of higher plants and

Amino acids are mostly synthesized from