Of Different Factors On Stomatal Response To Aba Sensitivity Of The Impact Studies

For understanding the effect of stomatal sensitivity in relation to xylem ABA, maize seedlings (Xiyu No.3) and Commelina comminnus were used, as experimental materials, to investigate the factors affecting the stomatal responses to ABA. The major results were showed as following:1. The soil water content gradually decreased with the progress of soil drying and no obviously differences were observed between high nitrogen and low nitrogen treatment. After re-watering, the soil water content recovered to the level of control within 2 days. Leaf water potential also gradually decreased as the soil drying, and the leaf water potential with the high nitrogen treatment was lower than that of low nitrogen treatment.2. After drying, leaf stomatal conductance decreased significantly and significant differences were observed between high nitrogen and low nitrogen treatments. The stomatal conductance with high nitrogen treatment was higher within the measuring period of this experiment higher than that with low nitrogen treatment.3. Soil drying treatment caused a significant and rapid increase in ABA content in the maize roots. The stimulation of ABA biosynthesis caused by soil drying was greater with low nitrogen treatment than that with high nitrogen treatment. Similar trend was showed with the xylem sap ABA, but no difference was observed in xylem ABA in response to soil drying between different nitrogen treatments. Root ZR content decreased with drought stress, and root ZR content in the case of high nitrogen was higher than that low nitrogen treatment. High nitrogen treatment, but no low nitrogen treatment, decreased the xylem ZR content when exposed soil drying.4. Stomatal conductance decreased with the increase in xylem ABA content, and there existed a obvious negative linear relationship. No obvious relationship between stomatal conductance and xylem ZR content was observed.5. The relationships between stomatal conductance and leaf water potential, xylem sap ABA, however, as the drying cycles proceeded, the responses of stomatalconductance was less sensitive to the decrease in leaf water potential. The relationship between stomatal conductance and xylem ABA kept constant after four drying cycles.6. The responses of stomatal opening and closing to ABA were modified sustantially by other factors, such as CaCl2, 6-BA and CO2, etc. CaCl2 increased the sensitivity of stomata to ABA, but COi had the opposite effect. 6-BA had an antagonistic effect against ABA effect on stomatal aperture.According to the above results, it was suggested that the relationship between stomatal conductance and xylem sap ABA was not a fixed characteristics, which might be modified by many other factors.