Abstract
Deficiency in Ca and P in mineral medium reduced the growth and nitrogen content ofAzolla pinnata but increased the content of soluble sugars in the plant; the deficiency in K and Mg was less effective in retarding the growth. The pH of the medium from 5 to 8 encouraged the growth and nitrogen fixation, whereas acidic pH of 4 as well as alkaline pH of 9 inhibited the growth and nitrogen fixation.