ORIGINAL ARTICLE

Leaf Photochemical Activity and Antioxidant Protection in Selected Hill Rice Genotypes of Koraput, India in Relation to Aluminum (Al3+) Stress

Genetic variation for Aluminum (Al³⁺) tolerance is prerequisite for developing cultivars with improved tolerance to Al3+ stress. The present study aims to assess genotypic variability of growth, photosynthesis along with antioxidant defense in popular hill rice landraces of Koraput, India under different concentrations of Al³⁺ and compare the responses with modern rice varieties to identify Al³⁺ tolerant rice genotypes. After exposure to different level of Al³⁺, the growth parameters such as shoot length, root length, fresh and dry weight of rice seedlings were significantly (P<0.05) inhibited in the studied genotypes compared to the control seedlings. Significant (P<0.05) reduction in SPAD index, chlorophyll and carotenoid content was observed in all rice seedlings under high concentration of Al³⁺. Higher concentration of Al³⁺ also alters the photo system (PS) II activity, as revealed in the reduction in the values of maximal fluorescence (Fm), maximum photochemical efficiency of PSII (Fv/Fm), yield of photochemical efficiency [Y(II)] and photosynthetic quenching (qP) with concomitant increase of minimal fluorescence (Fo) and non-photosynthetic quenching (NPQ). The antioxidant enzymes activities such as superoxide dismutase, ascorbate peroxidase and guaiacol peroxidase were increased in rice seedlings under elevated Al³⁺ concentrations. Taken together, hill rice landraces namely; Kalajeera, Machakanta, Haladichudi showed superior photochemical activity and better antioxidant protection than that of IR 64 cultivar. These hill rice landraces are identified as potential donors for the Al³⁺ tolerance breeding program.