A comparative study of effects of increasing concentrations of phosphate and phosphite on rice seedlings

Abstract

While phosphate (Pi) serves as an essential and indispensible plant nutrient, phosphite (Phi) acts as a potent herbicide. Despite their differential influence on plants, both the ions can attenuate phosphate starvation responses (PSRs). We analyzed and compared Pi and Phi uptake and accumulation, attenuation of PSRs and the morphological and physiological responses of the rice seedlings in response to the increasing concentrations of Pi and Phi. Our study revealed that increasing levels of Phi led to pronounced reduction in shoot and root mass in rice seedlings in comparison to similar Pi treatments. Phi inhibited root hair and root formation at 5 and 30 mM Phi concentrations, respectively. Whereas, higher Pi concentrations (40 and 50 mM) affected only root hair elongation. Increasing Phi dose led to drastic reduction in chlorophyll content which was not so in case of Pi. There was inverse relationship between external Pi/Phi level and anthocyanin content of the leaves. In comparison to 20 mM Pi treatment, similar dose of Phi led to significant downregulation of Pi transporters in both leaves and roots. Rice seedlings were found to accumulate mmol and µmol levels of Pi and Phi, respectively. Comparison of various PSR parameters revealed that in comparison to Pi, Phi exhibited greater degree of attenuation of PSRs. Lesser Phi accumulation and greater attenuation of PSRs by Phi indicate plant’s adaption to restrict entry of this toxic ion inside cells.