PHYSIOLOGICAL AND BIOCHEMICAL PARAMETERS OF NEWLY DEVELOPED SALT-TOLERANT RICE LINES UNDER CONTROLLED SALINITY

Abstract

This study evaluated four newly developed rice lines by measuring physiological and biochemical parameters, including chlorophyll content, leaf water content, catalase enzyme activity, and proline concentration. Under salinity treatment, chlorophyll a content in the new rice lines decreased to 6.30 - 6.97 μg/cm² (or 0.87 - 1.06 μg/mg), comparable to the control varieties Pokkali and Trang Cut, while IR29 and Bac Thom No.7 exhibited greater reductions, ranging from 10.65 - 11.20 μg/cm² (or 0.24 - 0.28 μg/mg). Chlorophyll b decreased slightly (1.10 - 2.33 μg/cm² or 0.13 - 0.28 μg/mg) with no significant differences among lines. Leaf water content in the new rice lines ranged from 76.60 to 79.03%, similar to Pokkali and Trang Cut, whereas IR29 was lowest (39.93%) and Bac Thom No.7 was 64.83%. Catalase activity decreased to 5.17 - 6.84 U/g in the new lines, comparable to the controls, while IR29 and Bac Thom No.7 showed larger reductions (10.73 - 11.13 U/g). Proline concentration increased to 1.02 - 1.13 μM/g in the new salt-tolerant lines, lower in Pokkali and Trang Cut (0.75 - 0.82 μM/g) and highest in IR29 and Bac Thom No.7 (1.50 - 1.65 μM/g). These physiological and biochemical parameters provide quantitative information on the responses of rice lines under salinity stress and form a scientific basis for further screening, development and selection of salt-tolerant rice varieties.