Studies On Alleviation Of Drought Tolerance In Peanut By Exogenous Application Glycinebetaine

Two peanut cultivars with different drought tolerance (drought-tolerant cultivar Luhua14 and drought-sensitive cultivar Hongbaibao-5) were used to study the effects of exogenous glycine betaine (GB) on the leaf water status, the osmotic adjustment, the antioxidant enzyme activities, the photosynthetic rate in leaves as well as the production. Peanut plants were grown either in pots or in the field.10 mM GB was irrigated to peanut seedlings with 4 leaves. 50 mM GB was sprinkled to the leaves at the anthesis stage and podding stage. We studied the protective mechanism of GB on the photosystem II (PSII) under drought stress. The main results are as follows:1. Effects of exogenous GB on water status of peanut seedlings under drought stress(1)In both cultivars of peanut, irrigation of 10mM GB could ameliorate water status in drought-stressed peanut leaves, increase leaf water potential (Ψw) and relative water content (RWC), this was related with h accelerating the accumulation of proline and soluble sugars and thus improving the osmotic adjustment (OA).(2)Exogenous GB protected activities of anti-oxidant enzyme (SOD,CAT). The GB-treated leaves exhibited a lower electrolyte leakage and MDA content, indicating that GB could stabilize the structure of membrane and alleviate the membrane lipid peroxidation resulting from active oxygen (ROS) under drought stress. (3)Exogenous GB alleviated the degradation of chlorophyll of peanut seedlings, improved the net photosynthetic rate (Pn), alleviated stomatal and non-stomatal limitation caused by drought stress and enhanced the stomatal conductance of drought stressed peanut leaves , thus strengthened the photosynthesis ability(4)Exogenous GB relieved the photoinhibition and photooxidation caused by drought stress and strong light, increased the max photochemical efficiency(Fv/Fm)under photoinhibition.2. Effects of exogenous GB at anthesis and poding stage on yield of peanut under drought stressSpraying peanut leaves with GB at anthesis and poding stages increased the production of both cultivars, especially at poding stage. Application of exogenous GB could improve the number of grains per individual plant, the number of plump grains and weight of per hundred grains. As well as, GB application improved the yield of peanuts under well-watered condition.