长期施氮对旱地小麦灌浆期叶绿素荧光参数的影响

探讨了长期施氮对黄土旱塬冬小麦灌浆期叶绿紊荧光的影响．结果表明，PSⅡ反应中心的实际光化学效率(φPSⅡ)随叶片水分胁迫的加剧而降低，施氮可明显提高φPsⅡ．施氮量为0kg·hm^-2、90kg·hm^-2和180kg·hm^-2三个处理中午时叶片的φPSⅡ分别为0．197、0．279和0．283，与上午相比分别降低了57．7％、56．4％和40．2％；下午各处理的φPSⅡ均得以恢复，0kg·hm^-2和90kg·hm^-2处理分别恢复到上午的87．3％和81．5％，180kg·hm^-2处理则完全恢复，并稍高于上午．施氮可提高PSⅡ的最大光化学量子效率(Fv／Fm)、光化学猝灭系数(qP)和非光化学猝灭系数(qNP)等荧光参数，表明施氮一方面提高了光能转换效率和PSⅡ的潜在活性，另一方面增强了过剩光能的非光化学耗散，有利于保护光合机构免受环境胁迫的破坏．但90kg·hm^-2和180kg·hm^-2施氮处理之间对光合的促进作用差异不显著，表明过量施氮无助于光合性能的提高，作物的光合能力并不随施氮量而同比例的改善。

Effects of long-term application of nitrogen fertilizer on leaf chlorophyll fluorescence of upland winter wheat

The effects of long-term nitrogen fertilization of chlorophyll fluorescence of winter wheat at its grain-filling stage on Loess Plateau highland were studied. The results showed that the actual photochemical efficiency of PS II reaction center (phi PS II) was decreased with leaf water stress aggravated, while was increased by nitrogen supply. The phi PS II of 0 kg.hm-2, 90 kg.hm-2 and 180 kg.hm-2 nitrogen treatments at noon were 0.197, 0.279 and 0.283, which decreased by 57.7%, 56.4% and 40.2% compared to that of morning, respectively. While they were all resumed at afternoon, even it was higher, for 180 kg.hm-2 nitrogen treatment, than that of morning. Maximum photochemical efficiency (Fv/Fm), photochemical quenching coefficient (qP), and non-photochemical quenching coefficient (qNP) were also increased by nitrogen supply, showing that the light energy conversion efficiency, and potential activity of photosynthetic reaction center and the non-photochemical dissipation of excess light energy, which resisted the damage on photosynthetic apparatus of environmental stress, were improved. No significant difference was found between 90 kg.hm-2 and 180 kg.hm-2 N treatments, which indicated that excess nitrogen was not favorable to photosynthetic performance, and photosynthetic capacity was not improved in proportion with nitrogen supply.