Effects of Drought Stress on Osmotic Regulation Substances of Five Catalpa bungei Clones

[Objective] This study aimed to investigate the effects of drought stress on osmotic regulation substances of Catalpa bungei clones. [Method] Potting experimental was carried out with plastic film sealing method, to differentiate the degrees of drought stress based on changes in soil water content and leaf water potential and investigate variations in contents of osmotic regulation substances（free proline,soluble sugar and soluble protein） in leaves of five Catalpa bungei clones under different degrees of drought stresses. [Result] According to changes in soil water content and leaf water potential, the whole process of drought stress was divided into normal level（CK, with soil water content of 97.49% and leaf water potential of-0.54MPa）, light drought（LD with soil water content of 59.96% and leaf water potential of-1.28 MPa）, mediate drought（MD with soil water content of 34.19% and leaf water potential of-2.32 MPa） and severe drought（SD with soil water content of 14.52%and leaf water potential of-2.99 MPa）. The soil water content and leaf water potential of five Catalpa bungei clones reached the highest correlation in exponential fitting, with an average R2of 0.989 3（P0.001）. The free proline content in leaves of five Catalpa bungei clones increased rapidly with the increasing degree of drought stress（P 0.001）. To be specific, free proline contents of Catalpa bungei clones015-1 and 7080 were 34.39 and 33.41 times of the normal level under severe drought conditions, which reached an extremely significant level（P0.001）; the free proline content of Catalpa bungei clone 1-3 rapidly increased to（855.46±227.52） μg/g Fw under light drought conditions. The soluble protein content in leaves showed different variation trends. To be specific, the soluble protein content of Catalpa bungei clone 7080 was the lowest at various drought stages and reached（1.644 ±0.137）mg/g Fw under normal conditions; the soluble protein content of Catalpa bungei clone 1-3 was relatively high under normal conditions and was reduced rapidly under light drought conditions, showing different response patterns. [Conclusion] Osmotic regulation substances in leaves of five Catalpa bungei clones all have certain response to drought stress. Free proline is the most important osmotic regulation substance, followed by soluble protein, while soluble sugar makes no significant contribution. According to changes in content of osmotic regulation substances, Catalpa bungei clone 7080 has relatively high capacity and good drought resistance, while Catalpa bungei clone 1-3 has the rapidest response to drought stress.

Response of Osmotic Regulation Substance Content and Protective Enzyme Activities to Shading in Leaves of Different Rice Genotypes

Effects of shading at the flowering and grain filling stages on osmotic regulation substance content and protective enzyme activities in the leaves of different rice genotypes （e.g., Ilyou 498, Gangyou 188, Dexiang 4103, Gangyou 527 and Chuanxiang 9838） were investigated. The results showed that the malondialdehyde content of Gangyou 188 significantly increased under shading, whereas those of Ilyou 498, Dexiang 4103, Gangyou 527 and Chuanxiang 9838 showed no significant differences compared to the control. The soluble sugar content significantly decreased in Ilyou 498, Gangyou 188, Dexiang 4103 and Chuanxiang 9838, whereas it did not significantly increase in Gangyou 527 under the weak light conditions （shading）. Moreover, the soluble protein content in the leaves of different genotypes tended to decrease under shading. Further, the protective enzyme activities in the leaves varied in different rice genotypes under the shading treatment. Based on the osmotic regulation substance content and the protective enzyme activities in the leaves of different rice genotypes, it was concluded that Gangyou 188 and Gangyou 527 had strong abilities to adapt to the low light conditions. In addition, the mechanism of damage to rice leaves in different genotypes under shading was discussed.

Response Mechanism of Plants to Drought Stress

Drought stress is an important factor affecting plant growth and development.It will provide a theoretical basis for cultivating new stress-resistant varieties and improving water utilization rate of plants by studying the regulation mechanism of osmotic adjustment and water transportation under drought stress,and understanding the physiological and biochemical characteristics and stress resistance mechanism.

Physiological Response of Spring Soybean Seedlings Under High-temperature Stress

To understand the response characteristics of soybean seedling resistance systems to high-temperature stress,the spring soybean varieties HN44 and HN65 were selected in this study as the experimental materials,as they had substantial differences in stress resistance.Soybean physiological status was studied under high-temperature stress.Sand culture was used in the experiment,and soybeans at the seedling stage were treated with high-temperature stress.The results showed that the activity of antioxidases and osmotic regulatory substance contents in soybean increased under high-temperature treatment for a certain period of time,the activity of antioxidases and osmotic regulatory substance contents decreased after continuous treatment,and high temperatures continuously increased malondialdehyde contents in the two varieties.At high temperatures,the antioxidant activity and osmotic regulator contents of HN44 were higher than those of HN65,and the malondialdehyde contents of HN44 were higher than those of HN65.The above results showed that HN44 soybeans exhibited significantly higher resistance to high-temperature stress than HN65 variety.