Co-application of selenite and phosphate reduces arsenite uptake in hydroponically grown rice seedlings: Toxicity and defence mechanism

The study empirically evaluates the abatement of As(III) uptake in rice seedlings (7d), in presence of Se and phosphate (P) under hydroponic condition. Positive correlation between As(III) translocation to the shoots of As(III) and P treated seedlings, shows P dependent As(III) translocation in rice. Whereas, presence of both P (5 and 10 μg ml−1) and (0.75 μg ml−1) of Se significantly reduces the As(III) uptake in rice seedlings. Application of Se alone also reduces As(III) uptake both in shoots and roots significantly, however, the seedlings suffers from lipid peroxidation. Among all the studied treatments, lower rates of P (5 μg ml−1) and Se (0.75 μg ml−1) when co-applied, significantly reduced As(III) translocation to the shoots without inflicting much toxicity in the seedlings which is manifested as significant increase in biomass with lower thio-barbituric reactive substances (TBARS). Also, significantly lower TBARS in seedlings receiving As(4)+Se(0.75) and higher TBARS in As(4)+Se(1.5), demonstrates that Se applied at lower rates (0.75 μg ml−1), lowers As induced toxicity. Higher SOD, APX and guaiacol peroxidase (POD) activities in As(4)+P(5)+Se(0.75) compared to that of As(4)+P(5) and As(4)+Se(0.75), supports that lower rate of P and Se provides tolerance towards As induced stress. The nitrogen metabolism in As(4)+P+Se treated seedlings is affected adversely at higher rates of Se and P application. Overall study concluded that application of lower rates of P (5 μg ml−1) and Se (0.75 μg ml−1) provides maximum amelioration of As(III) toxicity in rice seedlings.

► Application of P enhances As(III) uptake in rice, whereas Se(IV) reduces the uptake.
► As(III) uptake in rice shoots is significantly reduced by application of Se(IV) and P.
► Co-application of P and Se(IV) ameliorates the As(III) induced toxicity in rice.