[Effects of low temperature at 10 degrees C on some antioxidant enzyme activities and ultrastructures of hypocotylar cells in mung bean and garden pea].

Mung bean (Phaseolus radiatus Linn.) and garden pea (Pisum satium Linn.), which were stressed 4 days under a low temperature of 10 degrees C, were used as materials to study the cold tolerance of plant with different resistance. On the 2nd and 3rd day under 10 degrees C stress, both the malondialdehyde (MDA) content and the superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities increased significantly in hypocotylar cells of mung bean, so did SOD activity in garden pea, but other physiological indexes in garden pea were not different from the non-treatment groups (Figs. 1-5). In hypocotylar cells of mung bean, SOD activity always maintain at the highest level in a period of time,and so does POD activity (Figs. 3, 4). Ultrastructural results after stress indicated as follows: (1) Plastids in hypocotylar cells of mung bean accumulated much starch (Plate I-6), whereas the form of plastids in hypocotylar cells of garden pea changed maskedly to become dumb-bell-shaped, round or irregular, with the last one being the most common form (Plate I-8, 12); (2) In both mung bean and garden pea, central vacuole was divided into small vacuoles (Plate I-4, 10), and the number of mitochondria increased and became aggregated (Plate I-3, 11, 12). Judging from the activities of protective enzymes and ultrastructures, 10 degrees C low temperature caused non-lethal, temporary injuries to hypocotyls ultrastructures in mung bean, but no visible injury at all, and even improved its cold tolerance to a certain degree in garden pea.