Photosynthetic Characteristics And Yield Under Drought Stress And Evaluation Of Drought Tolerance Of Soybean Varieties

To investigate effects of drought stress on morphological characters,photosynthetic index and yield of soybean cultivars,ninety soybean varieties were used from Liaoning province,Shanxi Province and Hebei province in the pot experiment under drought stress during the flowering and pod periods.and identify of drought tolerance of soybean varieties.According to the identification and screening results,soybean varieties with drought resistant and drought susceptive were selected to stuty of the relationship between soybean photosynthetic and drought tolerance.Trying to provide a theoretical reference for soybean drought-resistant breeding and production,Results are listed as the following:1.Morphological charactersPlant height and stem weight of soybean were reduced under drought stress.Liaodou47,Jindou19,Liaodou45,Fendou62,Liaodou31,Tiedou54,Tiefeng24,Tiedou50,Jidou17 and Liaodou26 decreased slightly and were not sensitive to drought.Liaodou40,Tiedou53,Liaodou34,Tiefeng30,Liaodou10,Liaodou35,Tiedou55,Liaodou38,Liaodou33,Liaodou16and Liaodou12 decreased significantly and were sensitive to drought stress.2.Yield traitsThe pod number,grain number,pod weight and grain weight of soybean per plant were decreased under drought stress,and the varieties with small reduction were Liaodou45,Fendou62,Jindou31,Tiedou37,Liaodou26,Tiefeng24,Liaodou31,Liaodou54,Liaodou3,Liaodou47,Tiedou45,Jidou17,Liaodou33 and Tiedou50.The decreasing range is Liaodou37,Liaodou38,Liaodou34,Shennong6,Liaodou32,Liaodou21,Liaodou35,Liaodou10,Liaodou42,Liaodou40 and Liaodou15.3.Evaluation of drought tolerance of soybean varietiesAccording to the research results of three drought resistance evaluation methods including drought resistance coefficient,drought resistance index and subordinate function value,12 drought-resistant varieties were identified and screened,which were respectively Liaodou45,Jindou31,Fendou62,Tiedou37,Liaodou31,Liaodou3,Jidou17,Tiefeng24,Liaodou47,Tiedou45,Liaodou54 and Liaodou26.There are 11 drought-tolerant varieties,namely Shennong6,Liaodou37,Liaodou38,Liaodou34,Liaodou35,Liaodou15,Liaodou40,Liaodou32,Liaodou42,Liaodou10 and Liaodou12.4.The relationship between photosynthesis and drought toleranceNet photosynthetic rate,stomatal conductance,intercellular CO₂ concentration and transpiration rate were decreased of soybean under drought stress.The drought tolerance of soybean was negatively correlated with the decrease of net photosynthetic rate and stomatal conductance,and positively correlated with the decrease of transpiration rate.That is,under drought stress,the varieties with strong drought tolerance had a small decrease in net photosynthetic rate and stomatal conductance,but a large decrease in transpiration rate,while the non-drought tolerant varieties had a large decrease in net photosynthetic rate and stomatal conductance,but a small decrease in transpiration rate.Under drought stress,drought-tolerant soybean cultivars maintained relatively high net photosynthetic rate,stomatal conductance and transpiration rate,while drought-sensitive soybean cultivars showed the opposite.