Effects on Chlorophyll Fluorescence Parameters in Malus under Water Stress

The changes of chlorophyll fluorescence parameters in Malus seedlings were studied in simulating drought condition of nutrient solution cultivation containing 20% polyethylene glycol 6000 (PEG6000). PEG 6000-induced waterstress causes physiological changes in Malus. The results showed that Fv/Fo, Fv/Fm, q(p) and yield were decreased and q(N) was increased during the stress period. The changing extents in Fv/Fo, Fv/Fm, qp, qN and yield in the drought tolerant variety M. sieversii were lower than the drought resistive variety M. hupehensis. A remarkable increase of Of content was also observed when treated with water stress. Correlation analysis showed that there were negative linear correlations among F-v/F-m, yield and O-2(-), which indicated that the accumulation of active oxygen decreased the potential activities of PSII, the efficiency of primary light energy conversion and inhibiting electron transport of PSII.