Photosynthesis of <Emphasis Type="Italic">Rehmannia glutinosa</Emphasis> subjected to drought stress is enhanced by choline chloride through alleviating lipid peroxidation and increasing proline accumulation

Rehmannia glutinosa seedlings were pretreated with choline chloride (CC) in concentrations of 0, 0.7, 2.1 and 3.5 mM, and then subjected to drought and rewatering treatment to study the effects of CC on the generation of reactive oxygen species (O₂⁻, H₂O₂), lipid peroxidation, proline accumulation, water status and photosynthesis. The results showed that pretreatment with CC alleviated the inhibition of SOD and APX activity caused by drought stress, and therefore, the rate of O₂⁻ production and H₂O₂ concentration were reduced and lipid peroxidation decreased in pretreated plants. CC pretreatment also accelerated accumulation of proline, maintained higher Ψw and RWC, deferred leaf water loss during drought stress and retarded the drop in proline concentration after rewatering. Consequently, drought-induced decreases in F_m/F₀, F_v/F_m, Φ_PS2, q_P, and A and increase in q_NP were inhibited and the recovery of photosynthesis after rewatering was quicker in pretreated plants. Although differences in F_v/F_m, Φ_PS2 and q_P between treatments were not significant, there was a general trend that the effects of CC increased with the rise of its concentrations. The data suggested that 2.1 mM of CC be suitable for alleviating lipid peroxidation, promoting proline accumulation, retarding leaf water loss and improving photosynthesis of R. glutinosa seedlings under drought stress.