Choline chloride protects cell membrane and the photosynthetic apparatus in cucumber seedling leaves at low temperature and weak light

Choline chloride 1.07 mmol/L treatmentdiminished the saturated lipid contents of the fattyacid components mainly the phosphatidylglycerol(PG) resulting in the decrease of the saturation oflipid (Table 1), declined the permeability of cellmembrane and the production of MDA from lipidperoxidation (Fig.2) in the cucumber seedlingleaves under low temperature and weak light(6℃, PFD 100 μmol m-2 s-1). Furthermore, the cho-line chloride treatment alleviated the degradationof chlorophyll pigments especially chlorophyll b(Fig.1), the decrease in maximum photochemicalefficiency (Fv/Fm), the capture efficiency of excitedenergy (Fv'/Fm'), the photochemical quenching co-efficient (qp) and the actual photochemical effi-ciency (ΦPSII) of PSII (Table 2, Fig.3A, B C),and decreases in activity of antioxidant enzymessuch as POD, APX and CAT (Fig.4) in chilled leavesunder weak light. In addition, choline chloride treat-ment increased the non-photochemical quenching(NPQ) (Fig.3D) and the proline content (Fig.5)in chilled leaves under weak light. The aboveresults indicate that choline chloride protectedthe cell membrane and the photosynthetic ap-paratus in cucumber seedling leaves from chill-ing stress in weak light.