| Camellia sinensis originates in the southwest of China,perennial woody plant,lives in warm and humid climate conditions.H2S is an important signaling molecule,which plays an important role in plant response to abiotic stress.H2S signaling has been shown to induce plants to respond to a variety of stresses,such as drought,low temperature,salt,heavy metals,plant diseases and insect pests.However,the mitigation effect of H2S on drought stress of tea plants is rarely reported.The effects of exogenous H2S on seed germination and seedlings physiological characteristics of tea under drought stress were studied in this study.The main results were as follows:1.The results of seed germination experiments showed that H2S can significantlyalleviate the drought stress on the tea seed germination inhibition,and showed a concentration-dependent effect,the optimal concentration is 0.15 mmol/L.Further study found that H2S donor NaHS can significantly reduce the conductivity,MDA and O2·-of germinating seed roots,increase SOD activity,and then provide favorable conditions for the normal germination of tea seed under drought stress.Seed soaking and spraying had the effect of promoting seed germination under drought stress.The germination rates of 0.15 mmol/L seed soaking and spraying treatment were104.53%and 184.18%higher than those under PEG stress,respectively.The effect of promoting seed germination was the most obvious.The effect of spraying peeled tea seeds was better than that of non-peeled seeds.The germination rate of 0.15 mmol/L was21.82%,35.42%and 58.70%higher than that of stress.2.Effects of exogenous H2S on seedlings of tea plants under drought stress showed thatPEG-mimicking drought stress significantly reduced the contents of chlorophylla,chlorophyllb,carotenoids,and chlorophyll a+b in tea leaves.PEG-simulated drought stress treatment significantly increased the leaf electrical conductivity,MDA and O2.-level of tea leaves.The content of soluble sugar and proline was slightly higher than that of normal treatment group,and the dry weight and relative water content of leaves were significantly reduced.The addition of 0.15 mmol/L NaHS increased the biomass and chlorophyll content of the tea seedlings under drought stress,reduced the electrical conductivity,MDA,O2·-,soluble sugar and proline content.At the same time,the amount of endogenous H2S and NO in tea leaves under exogenous hydrogen sulfide were significantly higher than those under drought stress.The maximal fluorescence?Fm?,Fv/Fm,the electron transfer rate?ETR?,and the photochemical quenching coefficient?qP?were significantly reduced under PEG stress,initial fluorescence?Fo?and non-photochemical quenching coefficient?qN?increased significantly;addition of 0.15 mmol/L H2S increased the fluorescence parameters such as Fm,Fv/Fm,ETR,and qP,and keep the Fo and qN at lower levels.3.The effects of different exogenous substances in relieving the drought stress of teaseedlings showed that the electrical conductivity and MDA content in the treatment group with Na2SO3,Na2SO4,Na2S and H2S+NO scavenger cPTIO were significantly higher than those in the control group.Exogenous SNP and NaHS sprayed increased fresh and dry weight to a certain extent,significantly reduced the accumulation of O2·-in tea leaves under PEG stress,increased the content of proline,soluble sugar.MDA content was no significant difference with the control group.The electrical conductivity was lower than that of the drought stress group,which was close to the normal control group.At the same time,the activity of antioxidant enzymes?SOD,POD,CAT,GR and GPX?and glutathione content of tea plant increased,alleviate drought stress-induced oxidative damage.H2S has similar mitigating effects to NO during drought stress-induced seed germination and seedling growth inhibition,and the alleviation effect of H2S can be reversed by the NO scavenger cPTIO. |
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