EFFECTS OF DIFFERENT WATER DEFICIT PREVENTING TECHNIQUES ON CHLOROPHYLL FLUORESCENCE PARAMETER IN SUGARCANE (SACCHARUM OFFICINARUM L.) SEEDLING

摘要

Aims: The goal of the study was to evaluate the effects of different water deficit preventing techniques on the chlorophyll fluorescence parameters in sugarcane (Saccharum officinarum L.) seedling. Methods and results: A pot experiment was conducted in a greenhouse with three sugarcane varieties and three different levels of drought stresses under different water deficit preventive techniques. The results showed that there were higher values of F_0 especially in the controls of F172 and RCO10 comparing to the treatments under severe stress condition. This increment of F_0 values could be attributed to the destruction of reaction centers of PSII. The results also showed that the values of F_m (maximum fluorescence) and F_v (variable fluorescence) were lower in the controls than the treatments in all the sugarcane varieties and it could be a direct consequence of the thylakoids damage. The treatments proved their efficiency in enhancing the value's of F_v and Fm and decreasing the values of F_0, andit contributed to improve the net photosynthesis rate of the young cane seedlings. The results also indicated that under severe drought stress, the average values of F_v/F_m and F_v/F_0 were 0.604 and 1.909 in the controls, and 0.707 and 2.476 in the treatments, respectively, and it proved that the water deficit had caused the decreases of the efficiency of primary light energy conversion and the potential activity of PSII. Varieties with treatments of WA+PFM had the highest values of Fv/Fm and F_v/F_0,except the NW. The yield that represented the overall photochemical quantum and the ETR that was the electron transport rate had been also affected by the stress. The results showed that the severe drought stress caused decreases in the Yield of the control of ROC10 when compared with the treatments; decreases also occurred in the values of ETR in the controls when compared with the treatments in the 3 varieties. The average value of ETR was 19.38 mu mol (electron) m~(-2)s~(-1) in the treatments and 12.33 mu mol (electron)m~(-2)s~(-1) in the controls. However there were some irregularities in the cases of F172 and YT57/423 as far as the values of yield are concerned. All these changes could be a direct consequence of the whole photosynthesis process inhibition. Significance: The results of the present study could provide effective methods for improving the drought resistance in sugarcane plants in non irrigated upland fields.