Effects of Exogenous Abscisic Acid on Cell Membrane and Endogenous Hormone Contents in Leaves of Sugarcane Seedlings under Cold Stress

Sugarcane is the most important sugar crop in China and the world, which originated in tropical and subtropical areas and is a thermophilic crop. Extreme weather occurred frequently in worldwide that caused serious cold or frost damage in recent years, resulting in enormous losses in sugarcane production. Abscisic acid (ABA) regulates much important plant physiological and biochemical processes, and induces tolerance to different stresses including cold or frost damage. This experiment investigated the interrelationship between low temperature induced ABA biosynthesis and endogenous hormone balance using two sugarcane varieties, i.e. the cold tolerant variety GT 28 and cold susceptible variety YL 6. Plants were sprayed with ABA 12 h before cold treatment as opposed to the control group, where no additional substances were added. When the plants in the control group were exposed to cold stress, plant cell membranes were injured, and the GA(3) (Gibberellic acid 3) decreased, while the relative electric conductivity, MDA (Malondialdehyde), ABA, the ratio of ABA/GA(3), ratio of ABA/IAA (Indole acetic acid), and the ratio of ABA/ZR (Zeatin Riboside) all increased under the cold stress, and there are genotypic differences in response to the contents of proline, ABA and GA, and the ratio of ABA/GA exists between the sugarcane variety GT 28, cold tolerant and variety YL 6, cold susceptible under cold stress. The contents of proline and ABA and the ratio of ABA/GA are higher and the content of GA is lower in the cold tolerant variety, which is the vital physiological basis that caused two sugarcane varieties with different cold resistance. In the ABA treatment, the cell membrane injury was effectively alleviated and the contents of MDA and GA(3) decreased, but the contents of proline, ABA, and the ratio of ABA/GA(3) increased. The decreasing contents of MDA and GA(3), in contrast with the increasing contents of proline, ABA, and ratio of ABA/GA(3) in sugarcane leaves from the ABA treatment groups, were important factors that can effectively increase cold stress tolerance in sugarcane plants.