INVESTIGATION OF ARSENIC STRESS TOLERANCE POTENTIALITY OF PURPLE RICE

Abstract

Recently in Bangladesh, farmers in some areas such as Cumilla, Gaibandha are started to grow a purple-leaved rice. Very few information is available about purple rice. This plant contains high anthocyanin in its leaves and thus it has a strong antioxidant defense system. Arsenic is a serious environmental hazard. It causes physiological and structural disorders in plants. To our knowledge, though this rice plant is growing in our country but the literature about its arsenic-stress tolerance ability is absent. Therefore, we aimed to dissect its arsenic tolerance potentiality. To do this, we grew purple rice and BRRI Dhan-28 under different arsenic stress conditions such as 0 µM, 50 µM, 100 µM, and 500 µM. We performed similar experiments in BRRI Dhan-28 throughout the study to compare the results of purple rice. We measured the morphological and biochemical parameters of both rice varieties. We did germination test and result showed that the germination percentage of purple rice was lower than the BRRI Dhan-28 at different days. We measured plant height, root length and shoot length. The results showed that arsenic reduced plant height at 100 μꓟ and 500 μꓟ but not at 50 μꓟ. The root length and shoot length of purple rice were lower than the BRRI Dhan-28 but the decreasing rate of root and shoot length of purple rice was lower than the BRRI Dhan-28. Next, we did biochemical analysis of purple rice and BRRI Dhan-28. We measured anthocyanin content and result showed that purple rice contained higher anthocyanin content. Under stress condition, many biochemical changes occur in the plants. For example, proline is accumulated in plants under stress condition which is responsible for the mitigation of stresses. We measured proline content and the result showed that purple rice contains higher proline content than BRRI Dhan-28. The result showed that proline content of purple rice was increased under stress condition and the proline content of BRRI Dhan-28 was decreased. Result showed that catalase content of both varieties was increased under stress conditions. The plant height of purple rice was shorter than BRRI Dhan-28. The decreasing rate of root and shoot length of purple rice was lower than BRRI Dhan-28. From this observations, it can be said that purple rice possessed the higher arsenic tolerance potential than BRRI Dhan-28 in terms of higher anthocyanin content and proline content in purple rice in both stress as well as non-stress condition.