遮荫处理对灰木莲幼苗叶片光合氮利用效率的影响  

Photosynthetic nitrogen-use efficiency of Manglietia glauca seedling leaves under different shading levels

作　　者：唐敬超[1] 史作民[1,2] 罗达[3] 刘世荣[1] 

机构地区：[1]中国林业科学研究院森林生态环境与保护研究所,国家林业局森林生态环境重点实验室,北京100091 [2]南京林业大学南方现代林业协同创新中心,南京210037 [3]新疆林业科学院经济林研究所,乌鲁木齐830063

出　　处：《生态学报》2017年第22期7493-7502,共10页Acta Ecologica Sinica

基　　金：国家自然科学基金项目(31290223,31570240);中国科学院碳专项(XDA05060100)

摘　　要：以适生在我国南亚热带地区的珍贵树种灰木莲(Manglietia glauca)为研究对象,对其幼苗叶片的光合氮利用效率(PNUE)及影响因素在不同遮荫条件下的适应情况进行了研究,以期为这种珍贵树种的栽培育苗,以及人工纯林的改造提供科学理论依据。结果表明:60%遮荫条件下生长的灰木莲幼苗叶片光饱和净光合速率最高(Amax,6.03μmol m^(-2)s^(-1)),主要是由于60%遮荫条件下的灰木莲幼苗叶片具有最高的最大羧化速率(V_(cmax),32.93μmol m^(-2)s^(-1))及较高的最大电子传递速率(J_(max),61.83μmol m^(-2)s^(-1))。不同遮荫处理下的灰木莲幼苗叶片PNUE并没有显著差异,这是因为其在不同遮荫条件下的单位面积叶片氮含量(N_(area))及A_(max)会同步变化,核心是其分配到1,5-二磷酸核酮糖羧化酶/加氧酶(Rubisco)及生物力能学组分的氮比例(PR及PB)在不同遮荫处理下并没有显著差异。灰木莲幼苗叶片光合系统中捕光组分氮分配比例(PL)会随着遮荫程度的增加而显著增大,三个处理下的PL大小顺序为:90%遮荫(0.296 g/g)>60%遮荫(0.216 g/g)>全光(0.132 g/g),但这部分氮比例的提高并不会提高叶片的PNUE。灰木莲幼苗叶片捕光组分氮并不与细胞壁氮、Rubisco氮或者生物力能学组分氮形成协同变化,其随着遮荫程度的增加而增大的氮比例来源于其他氮库,这种变化是多因子综合作用的结果。因此在培育灰木莲幼苗时要进行适度遮荫,进行纯林改造时开出的林窗也不宜过大,要选择较为荫蔽的林下环境进行栽植;在遮荫的同时也要适度增施氮肥,以补充因捕光组分氮比例提高而造成的叶片氮消耗。Photosynthetic nitrogen-use efficiency （PNUE）, which （Amax） to nitrogen concentration in a defined leaf area （Narea）, is regarding their leaf economics, physiology, and strategy. The light is defined as the ratio of light-saturated photosynthesis considered an important trait for characterizing species environment may influence photosynthetic capacity and leaf nitrogen content, and may also influence biochemical factors that affect PNUE such as nitrogen allocation to the photosynthetic apparatus, CO2 diffusion from the atmosphere to the site of carboxylation, and specific activity of the photosynthetic enzymes. The objective of this study was to describe the inherent PNUE variation in leaves of Manglietia glauca seedlings grown under varying light environments. An improved understanding of this process is of great importance for M. glauca seedling cultivation and artificial pure forest modification. The results showed that Areax of M. glauca seedlings grown under 60% shade （6.03 μmol m-2 s-1 ） was higher than that under other shading levels, mainly because of a higher maximum carboxylation rate （ 32.93 μmol m-2 s-1 ） and a higher maximum electron transport rate （ 61.83 μmol m-2 s^-1 ）. Thus, moderate shading may assist in the cultivation and planting of M. glauca seedlings because Am,x improvement could significantly enhance their growth rate. No significant differences were observed in intercellular and chloroplast CO2 concentrations in M. glauca seedlings grown under different shading levels. Mesophyll conductance and stomatal conductance of M. glauca seedlings grown under 90% shade were lower than those under other shading levels. No significant difference was observed in the PNUE of M. glauca seedlings grown under different shading levels, because N changed synchronously with A which was largely attributed to the lack of significant difference in the proportion of total leaf nitrogen allocated to Rubisco and bioenergetics in such seedlings. Shading significantly enhanced the proport

关 键 词：光合氮利用效率 灰木莲 遮荫 氮分配 CO2导度 

分 类 号：Q945[生物学—植物学]