Differential fluoride uptake induces variable physiological damage in a non-aromatic and an aromatic indica rice cultivar

Abstract

The current study illustrates the systemic damages caused by increasing concentration of fluoride in non-aromatic rice variety, IR-64 and aromatic rice Gobindobhog (GB). Analysis of the physiological parameters like shoot length, root length and electrolyte leakage along with crucial damage indices like chlorophyll, malondialdehyde, H₂O₂ and protease activity indicated higher fluoride adaptation in GB compared to IR-64. IR-64 exhibited unregulated fluoride bioaccumulation when exposed to 25 mg L^-1 NaF stress, whereas fluoride uptake in GB was much regulated. Gene expression studies proposed that CLC2 rather than CLC1 mediated the fluoride import. Fluoride also triggered higher P-H⁺/ATPase accumulation in GB compared to IR-64, thus highlighting efficient homeostasis in stressed GB. Unlike IR-64, GB could maintain photosynthesis (RuBisCo expression), sugar metabolism (α-amylase expression and activity), glycolysis and Krebs cycle even under high concentration of fluoride stress. Fluoride also inhibited nitrate reductase activity in both the cultivars. The present research illustrates differential phytotoxicity emerging out of fluoride accumulation in rice seedlings, highlighting that IR-64 is a highly susceptible variety, whereas GB exhibits physiological plasticity and is better adapted to higher concentrations of fluoride.

Keywords: Damage; Fluoride; Metabolic pathways; Rice; Uptake.