Physiological response to drought and re-watering of different quinoa varieties

To investigate the effects of drought and rehydration on chlorophyll fluorescence and reactive oxygen species metabolism of quinoa seedling leaves, we used the quinoa varieties ‘Longli No.1’ (L-1), ‘Longli No.2’ (L-2), ‘Longli No.3’ (L-3) and ‘Longli No.4’ (L-4) as experimental materials. Seedlings were treated with drought stress for 10 days allowed to recover for 24 hours. Subsequently, chlorophyll fluorescence parameters F_o, F_m, F_v/F_m, F_v/F_o and non-photochemical quenching(NPQ), MDA contents, O₂·^- production rate, and the activities of antioxidant enzymes were determined. The results showed that compared with the un-stressed control (CK), F_o and F_m of the quinoa varieties ‘L-1’, ‘L-3’, and ‘L-4’ were decreased by 18.03%, 18.22%, and 7.72%, and 16.25%, 18.96%, and 10.64%, respectively, F_v/F_m , and F_v/F_o of the four different quinoa seedling leaves were decreased by 5.00%, 10.43%, 8.06%, 4.78%, and 16.84%, 30.71%, 25.44%, and 15.76% under drought stress, and NPQ was increased significantly. Simultaneously, MDA contents, and O₂·^- production rate were increased, and the activities of SOD, POD, CAT, and APX were all enhanced. After re-watering, F_o, F_m, F_v/F_m, F_v/F_o , and NPQ were all restored to the level of CK, but MDA content and O₂·^- production rate was not much higher than CK; the SOD in different quinoa seedlings was lower than CK; and POD, CAT, and APX were still higher than CK. In conclusion, re-watering treatment after drought stress will not only can recover the damage to the photosynthetic system in different quinoa seedling leaves but may also be helpful to alleviate the harmful effect that is caused by drought stress on seedling growth.