【摘要】 用氮浓度分别为2(低氮)、8(中氮)、32 g N·m-2·a-1(高氮)的NH4NO3溶液,喷淋盆栽夏蜡梅幼苗,以0 g N·m-2·a-1为对照(CK),1年后,比较其光合作用、相对叶绿素含量、叶绿素荧光参数、抗氧化酶活性及膜脂过氧化的差异,探讨氮沉降对夏蜡梅幼苗生理生态特性的影响。结果表明:3种氮处理下,夏蜡梅幼苗叶片的日均净光合速率(Pn)和最大净光合速率(Pnmax)比对照分别增加了14.7%、54.5%、26.4%和8.3%、66.1%、30.9%,中氮处理下的日均Pn、Pnmax值最高。不同氮浓度处理后夏蜡梅幼苗叶片的日均气孔导度均高于CK,以中氮处理最高;而日均胞间CO2浓度均低于CK,以中氮处理最低。光补偿点、暗呼吸速率均为中氮>高氮>低氮>CK,差异极显著;而光饱点为中氮>低氮>CK>高氮,差异极显著;表观量子效率为中氮>低氮>CK,差异极显著,高氮与CK差异不显著。不同氮浓度处理的相对叶绿素含量均明显高于CK,以中氮处理最高。PSⅡ原初光能转化效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)均为中氮>低氮>CK>高氮,差异极显著。不同氮处理的夏蜡梅幼苗叶片超氧化物歧化酶活性均高于CK,差异极显著,3种氮处理之间以高氮处理最高;过氧化物酶活性、丙二醛含量也以高氮处理最高,中氮次之,高氮、中氮处理与CK差异极显著,低氮处理与对照差异显著。不同氮处理的质膜离子渗漏为高氮>中氮>低氮>CK,差异极显著。本研究表明,不同浓度氮处理提高了夏蜡梅幼苗的光合作用能力,其中以中氮处理的效果最为明显,对其他生理指标也产生了一定的影响。更多还原

【Abstract】 We investigated the effects of simulated nitrogen deposition on the physiological and ecological characteristics of Sinocalycanthus chinensis seedlings by adding various amounts of NH4NO3in a pot experiment.Three levels of NH4NO3included:low-N(2 g N m-2·a-1),medium-N(8 g N m-2·a-1),and high-N(32 g N m-2·a-1),with 0 g N m-2·a-1as the control.After one year,we measured the photosynthetic characteristics,relative chlorophyll content,chlorophyll fluorescence parameters,membrane lipid peroxidation,and antioxidant enzyme activities in leaves of S.chinensis seedlings among the different treatments.The diurnal mean values of net photosynthetic rate at the low,medium,and high levels of N addition were 14.7%,54.5%,and 26.4% higher than that of the control,respectively;the maximum net photosynthetic rates were 8.3%,66.1%,and 30.9% higher than that of the control,respectively.The highest values for net photosynthetic rate and maximum net photosynthetic rate were recorded for the medium-N level.The daily mean stomatal conductance was higher in all N treatments than in the control,and the highest value was recorded for the medium-N level.However,the intercellular CO2concentrations were lower in all N treatments than in the control;the lowest value was recorded in the medium-N treatment.The light compensation point and dark respiration rate among the four treatments were in the order of medium-N > high-N > low-N > control,with highly significant differences among the treatments.In terms of the light saturation point,the treatments were ranked as follows:medium-N > low-N > control > high-N,with highly significant differences among the treatments.The apparent quantum yield values were ranked as follows:mediumN > low-N > control;however,there was no significant difference between the high-N treatment and the control in the apparent quantum yield value.The relative chlorophyll contents in seedlings in the three N treatments were significantly higher than that in the control,with the highest values recorded in the medium-N treatment.The primary chemical efficiency and potential activity of photosystem II in S.chinensis seedlings were ranked as follows:medium-N > lowN > control > high-N,with highly significant differences among the treatments.The superoxide dismutase activity,peroxidase activity,and malondialdehyde contents in S.chinensis seedlings in the medium-and high-N treatments were significantly higher than those in the control,but there was no significant difference in these parameters between the low-N treatment and the control.The membrane permeability of S.chinensis seedlings was ranked from most permeable to least permeable as follows:high-N > medium-N > low-N > control,with highly significant differences among the treatments.These results suggested that appropriate nitrogen levels,especially the medium-N level,can enhance the photosynthetic ability of S.chinensis seedlings,and also affect other physiological indexes to some extent.更多还原