Effects Of Water Stress On Growth And Development, Physiological Characteristics And Nutrient Distribution Of Soybean

Soybean cultivar ZhongHuang 13 was used in pot in this experiment.Four water stress levels were carried in 2 growing periods,â‘ A period: from the branch to the maturity stage andâ‘¡from the flowering to the mature stage. In each period of stage, four water stress levels were:â‘ normal irrigation treatment (Treatmentâ… ), 75%-80% of the field maximum moisture capacity in soil water content;â‘¡slight water stress(treatmentâ…¡), 60%-65% of the f field maximum moisture capacity in soil water content;â‘¢mild water stress (treatmentâ…¢) , 50%-55% of the field maximum moisture capacity;â‘£severe water stress (treatmentâ…£) , 35%-40% of the field maximum moisture capacity in soil water content. Plant height, the number of pods, leaf area, dry matter accumulation and distribution, the chlorophyll content, net photosynthetic rate, transpiration rate, stomatal conductivity, stomatal characteristics, stomatal limitation value, the content of N, P, Ca, Mg, Zn and soluble sugar through growing period.The growth and development characteristics, physiological characteristics, the distribution of dry matter and the nutrients and their relations have been analysised. The results were as following:1. The plant height, leaf area decrease as water stress increase.2. There are large differences in dry matter accumulation among treatments. As stress increased and advanced, the total dry matter reduced. Less dry matter partitioned to reproductive organs when soybean subjected to water stress conditions, except to slight water stress treatment in A period. On the country, under severe water stress more dry matter was partitioned to root as compared with other organs.3. The yield decrease as water stress increases. Under slight and mild water stress conditions, soybean yield reached a higher level in A period, while the yield was much higher under severe water stress in B period. Treatmentâ…¡-A obtained the highest yield among all treatments. The results suggested that slight water stress might increase yield.4. Relative chlorophyll content decreases sharply from seed-filling period, and the decrease slows down as water stress increases, indicating that antagonistic ability of leaves is enhanced by slight water stress in A period, and the ability that can adapt to environment under water stress is gradually enhanced along with period of duration advancement.5. As stress became stronger and advanced, the stomatal density of soybean leaves increases; The changing trend of stomatal area was similar to the stomatal perimeter under water stress.6. Soybean leaf photosynthesis rate and stomatal conductance show a downward trend under water stress. From 14h to 16h, non-stomatal limitation play dominant role in decline of photosynthesis under normal irrigation. The fall of photosynthesis rate at noon is brought by non -stomatal limitation under other water stress treatment. The results showed that the non-stomatal limitation of photosynthesis happens in advance under moderate and severe water stress.7. As water stress increased, the nitrogen and soluble sugar content increased, while P, Ca, Mg, Zn content decreased. Each element accumulated in root decreases nearly to zero under water stress. At the maturity stage, the partition ratio of each element in the pod is much higher than in any other organs, except calcium element.