Effect Of Low Phosphorus Stress On Photosynthetic Characteristics Of Different Wheat Genotypes

Phosphorus (P) deficiency is one of the limiting factors to wheat production. Screening and breeding of low P tolerant wheat genotypes would be one of effective alternatives to alleviate low phosphorus stress and to increase the utilization efficiency of P fertilizer. Understanding the nutritional and physiological mechanisms of wheat plant adaptation to low phosphorus stress would be very helpful to the above program of screening or breeding. Effect of low phosphorus stress on leaf photosynthesis characteristic, the lipid content in the thylakoid membrane, the function of PSII and antioxidant enzymes activity was studied in the present study use jing411 and xiaoyan54 wheat under l low phosphorus stress. The results obtained were summarized as follows:(1) Low phosphorus stress resulted in a decrease in biomass, length of root and an increase in the number of root in wheat. And such a change was much greater in jing411 plants than that in xiaoyan54 plants.(2) Low phosphorus stress decreased photosynthetic rate in jing411 and xiaoyan54. Under low phosphorus stress conditions photosynthetic rate of xiaoyan54 and jing411 were decreased by 59.60% and 63.73%, respectively. Low phosphorus stress decreased the stomatal conductance, and increased the intercellular CO2 concentration (Ci) in both genotypes, indicating that the decrease of photosynthetic rate of wheat leaves under low phosphorus stress was due to non-stomatal limitation.(3) Low phosphorus stress decreased the lipid content in the thylakoid membrane of wheat leaves. The decrease of PG contents was much less in xiaoyan54 plants than that in jing411 plants. This may be important in mitigating the degradation of LHCII which binding to PSII. Low phosphorus stress increased the SQDG content for both genotypes.(4) Low phosphorus stress increased initial fluorescence (Fo), and decreased conversion efficiency of primary light energy of PSII (Fv/Fm). Therefore, the potential photosynthetic activities had been inhibited, which affected the light energy conversion and yield at last. The photosystem of xiaoyan54 is less destroyed and more tolerant to low phosphorus stress than jing411.(5) Low phosphorus stress resulted in an increase in ROS content and antioxidant enzymes (SOD, APX, POD, CAT) activities in wheat. The increase of antioxidant enzyme activity was much greater in xiaoyan54 plants than that in jing411 plants, while the increase of ROS content was less than jing411.