施氮量对烤烟打顶期叶片光合响应的影响

摘要

In order to identify the relationship between nitrogen application rates and photosynthetic characteristics of cutters at topping stage in flue-cured tobacco, a pot experiment was carried out to study the effects of nitrogen levels on light response parameters of cutters at topping stage. Three levels of nitrogen fertilizer (45, 90 and 135 kg/ha) were set up in pot experiment. Net photosynthetic rate(Pn), intercellular CO2 concentration (Ci) and transpiration rate (E) of cutters were measured in an open-circuit gas channel system, meanwhile, instantaneous light use efficiency (LUEi) and instantaneous water use efficiency (WUEi) were calculated out. The results showed that as the levels of photosynthetically active radiation increased,Pn of cutters at topping stage in flue-cured tobacco gradually increased and stabilized; as the levels of nitrogen fertilizer increased,Pn,Ci and LUEi of middle leaves decreased, and the same pattern was found on the apparent quantum efficiency (AQY), maximum net photosynthetic rate (Pmax) and light compensation point (LCP). WUEi and light compensation point (LCP) were reduced with 45 kg /ha applied in pot experiment. Based on this study, an optimum nitrogen rate of between 45 kg/ha and 90 kg/ha was recommend to ensure strong photosynthetic capacity of cutters at topping stage in flue-cured tobacco.%为进一步明确氮肥施用量与烤烟打顶期中部叶片光合作用的关系，设置了3个氮肥水平45、90和135 kg/hm2，在盆栽试验条件下研究了不同施氮量对烤烟打顶期中部烟叶光响应曲线及其拟合参数的影响。采用开放式气路测定了烤烟中部叶净光合速率、胞间 CO2浓度和蒸腾速率，并计算了瞬时蒸腾速率和光能利用效率。结果表明，随着光合有效辐射水平增强，打顶期中部烟叶净光合速率逐渐提高并趋于稳定；但增加施氮量，叶片净光合速率、胞间 CO2浓度和瞬时光能利用效率逐渐降低，表观量子效率、最大净光合速率和光补偿点随之降低；施氮为45 kg/hm2的叶片瞬时水分利用效率和光补偿点最低。综上所述，盆栽试验条件下，施氮量为45~90 kg/hm2有利于增强烤烟打顶期中部叶片的光合响应。