What is the significance of nodulation index?

What is the significance of refractive index?

What is the importance of root nodule?

What is the name of nitrogen fixing bacterium found in the root nodules of legumes ?

What is significant number? What is significant digit?

What is the function of leghaemoglobin in root nodules of legumes (Pea, Beans, Gram)?

What is pH? What is its significance?

Roots in gram, groundnut,pea, barseem bear small nodule like swellings. What is the function of root nodules?