| The effects of drought stress on the germination rate,germination potential and germination index of Cerasus campanulata seeds were investigated by simulating drought stress by PEG-6000 with six gradient concentrations(0%,5%,10%,15%,20%and 25%)on the germination rate,germination potential and germination index of C.campanulata.After treating 0d,1d,3d,5d and 7d of C.campanulata seedlings with PEG-6000 of the above six gradient concentrations,the relative water content,chlorophyll content,photosynthetic index,malondialdehyde content,proline content,soluble sugar content,soluble protein content and the activities of the three protective enzymes CAT,POD and SOD were determined.In order to explore the drought resistance physiology of C.campanulata seeds and seedlings,it provides a theoretical basis and data reference for the introduction and cultivation of C.campanulata in arid and semi-arid areas.The specific results are as follows:(1)With the increase of PEG-6000 concentration,the germination rate,germination potential and germination index of C.campanulata seeds showed a trend of first rising and then declining.Under the stress of 5%concentration PEG-6000,the germination rate of C.campanulata seeds was the highest,reaching 71.00%,which was 6.56%higher than that of the control group.The soluble sugars and soluble proteins of the seeds showed a tendency to rise first and then decline with the prolongation of stress time,and eventually lowered than the level of the control group.The germination potential and germination index of seeds increased at 5%concentration,and were 1.17 times and 1.20 times higher than those of the control group,respectively.(2)High concentration of PEG-6000 stress will inhibit the individual growth of C.campanulata,when the concentration of PEG-6000 reaches more than 15%,the growth of C.campanulata seedlings is inhibited,and the plant wilts.The relative water content and chlorophyll content of the leaves of C.campanulata showed a downward trend with the intensification of the degree of stress,and when the stress was the most severe,the relative water content and chlorophyll content of the leaves decreased by 57.1%and 62.4%respectively.Under the pressure of PEG-6000,the photosynthetic index related to water in C.campanulata showed a downward trend.By the late stage of stress,the photo synthetic rate,stomatal conductance and transpiration rate of the plants decreased to a very low level,the photo synthetic rate decreased to 27.5%of the control group,the stomatal conductance decreased to 0.1 mol·m-2·s-1,and the transpiration rate decreased to 8.2%of the control group.(3)Malondialdehyde content shows an upward trend with the prolongation of PEG6000 stress time,and the higher the concentration of PEG-6000,the greater the increase in malondialdehyde content.Under the pressure of 25%concentration PEG-6000,the malondialdehyde content was 96.4%higher than that of the control group,and the plants were seriously poisoned by reactive oxygen species.Under PEG-6000 stress,proline content showed a trend of first rising and then decreasing,and after 5 days of PEG-6000 stress treatment,the proline content of C.campanulata seedlings was lower than the normal growth level.Under short-term stress,the higher the concentration of PEG-6000,the greater the increase in the content of soluble sugars,soluble proteins and other osmotic regulatory substances in the leaves of C.campanulata,but under continuous stress,the osmotic substance content will gradually decrease.Under the stress of PEG-6000 below 15%,the activities of the three protective enzymes POD,SOD and CAT showed an upward trend with the prolongation of the stress time;under the simulated drought stress of 20%PEG-6000,the activities of the three protective enzymes increased first and then decreased with the prolongation of the stress time,and in the late stage of the stress,the SOD activity was 56.7%lower than that of the control group.(4)According to the comprehensive analysis of variance contribution rate and factor score of each common factor,the 1st D of 5%concentration PEG-6000 stress treatment,C.campanulata had the highest comprehensive score of drought resistance,with a comprehensive score of 0.6275,7th d of 25%concentration PEG-6000 stress treatment,and the lowest comprehensive score of drought resistance of C.campanulata,with a comprehensive score of-1.9483.The above studies show that the low concentration of PEG-6000 treated with C.campanulata seeds can improve seed vitality and enhance seed germination neatness.Low concentrations of PEG-6000 stress can stimulate plants to develop a stress response,improving the plant’s drought resistance.Continuous PEG-6000 stress will reduce the relative water content and chlorophyll content of the leaves of the C.campanulata,inhibit the photosynthesis of the C.campanulata,cause the malondialdehyde content in the plant to increase,reduce the proline content and protect the enzyme activity,causing damage to the growth of the plant,and the higher the concentration,the more serious the damage. |
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