Effects of Drought Stress and Re-watering on Photosynthetic Characteristics of Maize Seedlings

Effects of different treatments of drought stress and re-watering on photosynthesis of maize were studied to optimize measures of restraining growth of maize seedlings.The maize variety，Zhengdan 958 was used as material.Hydroponics was used to study photosynthetic physiological indexes of maize seedlings under different treatments of drought stress and re-watering，such as content of photosynthetic pigments，photosynthetic parameters，chlorophyll fluorescence parameters etc.With increasing of drought stress cycles，contents of chlorophyll and carotenoid decreased first and then increased，and increased first and then decreased，respectively.The maximum photochemical efficiency（Fv/Fm），actual photochemical efficiency（ΦPSⅡ）and photochemical quenching coefficient（qP）of PSⅡ decreased first and then increased，while non photochemical quenching coefficient（qN）increased first and then decreased.Under drought stress，net photosynthetic rate（Pn），stomatal conductance（Gs），transpiration rate（Tr）and water use efficiency（WUE）of maize decreased significantly，while intercellular CO2 concentration（Ci）increased significantly（P＜0-05）.The maximum net photosynthetic rate（Pnmax），apparent quantum efficiency（AQE）and dark respiration rate（Rd）decreased significantly，while light compensation point（LCP）increased significantly（P＜0-05）.After re-watering，the chlorophyll content，Pnmax，AQE，LCP and light saturation point（LSP）showed increasing trends，while Rd showed a decreasing trend.Pn，Gs，Tr，Ci，WUE，Fv/Fm，ΦPSⅡ，qP and qN increased with the extension of re-watering gradually，showing a certain compensation effect.However，Pn and WUE were still very low after treatments of 3 times of drought stress and re-watering，and even decreased to a negative value when 3 days after re-watering.The compensatory water absorption was significant under treatments of 2 times of drought stress and re-watering，while the treatments of 3 times of drought stress and re-watering might cause some damage to maize seedlings，compensation effect was limited after re-watering.In conclusion，times of drought stress should be strictly controlled in restraining growth of maize seedlings，in order to avoid damage to plants and affect growth of seedlings.