Joint Effects Of Cytokinin And Nitrogen On Drought Tolerance Of Creeping Bentgrass (Agrostis Stolonifera)

To research effects of cytokinin and nitrogen on drought resistance reactions and mechanisms of creeping bentgrass(Agrostis stolonifera), the study investigated impact of cytokinin and nitrogen on growth and metabolic activities in drought stressed creeping bentgrass. Creeping bentgrass of ’PennA-4’ treated with three rates of CK (trans-zeatin riboside,0,10 and 100 μM, designated by CK0,10, and 100) and two nitrogen rates (2.5 and 7.5 kg N ha-1 every 15 days, designated by low and high N) in a complete factorial arrangement was grown under two soil moisture regimes:well-watered and drought stress. The results showed that:1. Under well watered condition, CK100+ high N treatment enhanced turfgrass quality of creeping bentgrass.2. Under drought stress regime, CK10 and CK100 improved turfgrass quality, chlorophyll content and leaf relative water content of creeping bentgrass, delayed the leaf wilting. During the drought period, high N treated grass showed higher turfgrass quality, chlorophyll content and leaf relative water content than low N treated grass.3. Drough stressed creeping bentgrass had higher levels of ROS, MDA and electrolyte leakage relative to well watered creeping bentgrass. Exogenous CK reduced ROS, MDA and electrolyte leakage of creeping bentgrass under moisture stress, specially in high N condition.4. Drought stress led to significant decline in the activities of SOD, APX, CAT and POD, but both CK10 and CK100 treatments showed the positive effects to maintain the enzyme activities. In addition, high N treatment enhanced the activities of SOD, APX, CAT and POD by 7.6%,17.7%,5.8% and 13.0%, respectively, relative to low N treatment.5. Under moisture stress, SOD, APX, CAT and POD isozymes in the grass treated with CK 100 showed stronger stain intensity than the grass treated with CKO. And high N plants exhibited a stronger intensity of CAT and POD isoforms than low N plants.6. Drought stress led to significant reduction in nitrate reductase activity, root mass and root viability of creeping bentgrass relative to well watered condition. But exogenous CK enhanced the nitrate reductase activity, root mass and root viability of creeping bentgrass under drought stress. Moreover, high N treatment improved nitrate reductase activity, reduced root mass and root viability of creeping bentgrass under drought stress.Our results demonstrated the beneficial impacts of CK and N on physiological reactions, especially antioxidant metabolism, and CK at 100 uM plus high N rate may be the best application combination to improve drought stress resistance of creeping bentgrass.