Potentiality of Azolla as a suitable P-biofertilizer under salinity through acid phosphatase activity

The cellular and extracellular acid phosphatase (APase, Electrical Conductivity (EC) 3.1.3.2) activities in different Azolla spp. were induced in P-deprived condition after 48 h and maximum was on the 12th day of incubation. APase activity has been investigated at different levels of NaCl. Highest cellular and extracellular APase activities were observed in A. microphylla at 20 (2-fold of the control) and 30 mM (3.2-fold of the control) NaCl, respectively, while lowest were in A. filiculoides. Presence of different concentrations of micro- and macronutrients in saline medium regulated the APase activity of the Azolla. Ca2+ played a major role in enhancing the APase activity under salinity. Heavy metals did not affect APase activity at the lower level, whereas its higher level inhibited the activity. The enhancement in the APase activity under moderate salinity suggests the major contribution of APase activity during salt-responsive physiological adaptation of Azolla possibly by providing maximum inorganic phosphate to the association, which might be helpful in compensating for the energy crisis caused by salt-induced inhibition in photosynthetic machinery and also in regulating the nutrient imbalances during salt shock or process of adaptation towards heavily polluted agricultural land.