为探明玉米苗期不同叶龄叶片光合特性对涝渍胁迫的响应差异。以玉米品种浚单20为试验材料,采用盆栽方法,在4叶期开始水分处理,设置CK(土壤相对湿度70%-80%)、淹水3、5、7 d和渍水5、10、15 d共7个处理,比较涝渍条件下不同叶龄叶片净光合速率、蒸腾速率、气孔导度、细胞间CO2浓度及SPAD值的变化。结果表明,苗期淹水和渍水均显著降低了玉米叶片的SPAD值,淹水影响程度大于渍水,其中淹水7 d和渍水7 d 叶片的SPAD值分别比对照降低37.9%和3.3%。不同叶龄叶片的光合特性对涝渍响应存在差异,叶龄大的叶片抗涝渍能力相对较强。涝渍≤7 d时新出生的第5叶和第6叶的净光合速率、蒸腾速率和气孔导度显著下降；涝渍胁迫7 d时,渍水和淹水的净光合速率分别比CK降低18.5%和15.4%；渍水15 d时,第9叶的净光合速率比CK偏高6.1%,表明玉米对涝渍的适应性逐渐增加。导致净光合速率下降的因素随涝渍持续时间而变化,涝渍1～3 d以非气孔因素影响为主,5～10 d时气孔因素占主导地位。光响应曲线模拟结果显示,涝渍胁迫使最大净光合速率和光饱和点分别降低15%～61%和8.0%～43.9%,光能和水分利用效率下降,光补偿点和暗呼吸速率降低,这表明叶片可通过增强弱光条件下光合能力和减少自身能量消耗来调整对涝渍的适应性。
英文摘要:
China locates in the monsoon climate zone of East Asia, where the precipitation during summer makes up more than 50% of the annual total in most regions, and at that time farmlands always suffer waterlogging disaster caused by too large amount of precipitation in the short term and poor drainage. Waterlogging stress is one of common natural disasters that hinder agricultural production, which may occur and does great harm to maize (Zea mays L.) at any growth stage. The sensitivity of maize to waterlogging in different growth stages is different and seedling is the most sensitive to waterlogging. Crops could adapt themselves to waterlogging through morphological or physiological self-regulation under successive waterlogging at the same time. This paper deals with the differences in the responses of chlorophyll content and photosynthetic characteristics of maize seedling leaves at different foliar ages to waterlogging stress. A total of 7 water treatments, including CK, 3, 5 and 7d of flooding and 5, 10 and 15d of waterlogging, for the tested maize cultivar XD20 began at the 4-leaf stage to make a comparative analysis of the changes in the net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentration and SPAD value of leaves at different foliar ages under waterlogging conditions. Results indicate that flooding and waterlogging at seedling stage significantly reduced the SPAD value of maize leaves, and flooding affected maize more greatly than waterlogging. The SPAD value of leaves after 7d of flooding and 7d of waterlogging was 37.9% and 3.3% lower respectively than CK. The photosynthetic characteristics of leaves at different foliar ages presented varied responses to waterlogging. When the number of waterlogging days was ≤ 7d, the net photosynthetic rate, transpiration rate and stomatal conductance of the new 5th and 6th leaf significantly dropped; after 7d of waterlogging, the net photosynthetic rate of the waterlogged and flooded leaves was 18.5% and 15.4% lower respectively compared with CK; after 15d of waterlogging, the net photosynthetic rate of the 9th leaf rose by 6.1% compared with CK. The net photosynthetic rate after 1-3d of waterlogging dropped mainly due to the effects of non-stomatal factors, while the stomatal factors were the main reason after 5-10d of waterlogging. The light response curve simulation shows that waterlogging stress caused a decline of 15%-61% and 8.0%-43.9% in the maximum net photosynthetic rate and light saturation point respectively, and light and water use efficiency declined, so did the dark respiration rate and light compensation point. The adaptability of maize increased with waterlogging duration. With relatively strong resistance to waterlogging, the leaves of higher foliar age index can adjust their adaptability to waterlogging through enhancing their photosynthetic capacity under low light conditions and reducing their energy consumption.
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