Effect of exogenous abscisic acid on improving low-phosphorus (P) response in rice (<italic>Oryza sativa</italic> L.)

AbstractPhosphorus (P) deficiency is a major constraint to rice productivity worldwide. Exogenous application of abscisic acid (ABA) has not been reported to improve rice response toward P-deficiency. Present study analyzed the biochemical response in the shoots and roots of two rice cultivars, CSR10 (low-P tolerant) and Pusa44 (low-P susceptible) at 36, 72 and 216 h after normal P (NP) (10 ppm) (control), low P (LP) (1 ppm), and LP + ABA given to 12-d old seedlings. Results found that biomass and P-uptake reduced in Pusa44 compared to CSR10 under LP but improved significantly under LP + ABA. P-fractionation was utilized efficiently by CSR10 under LP while LP + ABA improved P-fractionation in both cultivars. LP + ABA improved acid phosphatases in both cultivars. Hexose and sucrose levels were depleted while starch hydrolyzed poorly in Pusa44 compared to CSR10 under LP while LP + ABA enhanced starch hydrolysis and levels of sugars in both cultivars. Starch increased at a late stage in the roots of CSR10 under LP while Pusa44 improved it under LP + ABA. Antioxidant capacity was low while H2O2 was high at early stage in Pusa44 compared to CSR10 under LP. LP + ABA improved antioxidant capacity and reduced H2O2 in both cultivars. Results concluded that ABA is a versatile regulator of not only P-acquisition/P-utilization but also carbohydrates and antioxidant activities under P-deficiency, and exogenous ABA improved low-P tolerance in rice. [ABSTRACT FROM AUTHOR]