底泥养分富集条件下11种水生植物的光合氮利用效率

Photosynthetic nitrogen-use efficiency of 11 aquatic plant species under eutrophication of the sediment from a brooklet in Guangzhou

为揭示水生植物对富营养化河涌底泥的生理生态适应性及其净化能力,选取11种水生挺水植物(包含6种本土植物和5种外来植物)结合河涌底泥进行试验。通过测定试验一年后植物叶片的光饱和光合速率(P_(sat),μmol m^(-2)s^(-1))、比叶面积(SLA,m^2/kg)、总氮含量(TN,mg/g)和光合作用氮利用效率(PNUE,μmol mol^(-1)s^(-1)),比较分析物种间生理与结构特性及其相互关系。结果表明:种间的SLA层次比较分明,最高的大叶皇冠草(20.31±0.30)与最低的鸢尾草(7.22±0.31)相差近3倍。种间的P_(sat)在(3.76±0.57)(鸢尾草)—(21.53±1.20)(水罂粟)之间,水罂粟比鸢尾草高81.79%。种间的PNUE从42.53±8.42(鸢尾草)至655.8±100.93(天使花),美人蕉、水罂粟、风车草和香蒲的PNUE值均较高,且差异不明显(P>0.05),这些植物的PNUE显著高于较低PNUE的种类(包括菖蒲、蓝花草和鸢尾草)(P<0.05)。种间SLA分别与PNUE和P_(sat)(μmol kg^(-1)s^(-1))呈显著的正相关,SLA和P_(sat)(μmol m^(-2)s^(-1))分别与TN(mmol/m^2)呈显著负相关(P<0.05)。外来植物类群的PNUE、SLA、P_(sat)和TN均显著高于本地植物类群(T-test,P<0.05),说明外来水生植物在养分富集化环境下能更有效地利用资源,具有潜在的高生长速率和种间竞争优势。

To investigate the ecophysiological adaptability and purification capacity of aquatic plants for eutrophication of sediment, 11 emergent aquatic plant species growing in eutrophied sediment from a brooklet in Guangzhou were studied in relation to leaf physiological and structural traits. The aquatic plants comprised six indigenous plant species and five exotic plant species. In this study, after 1 year, the light-saturated photosynthetic rate （Psat, μmol m-2 s-1）, specific leaf area （SLA, m2/kg）, total nitrogen content （TN, mg/g）, and photosynthetic nitrogen-use efficiency （PNUE, μmol mol-1 s-1） in leaves of the 11 aquatic plant species were measured and their inter-relationships were analyzed. Changing gradients of interspecific SLA were clearly detected among the plant species. There was a nearly three-fold difference in SLA between the maximum shown by Echinodorus macrophyllus （20.31±0.30） and the minimum in Iris tectorum （7.22±0.31）. Interspecific Psat values of the plant species were between 3.76±0.57 （I. tectorum） and 21.53±1.20 （Hydrocleys nymphoides）. The Psat of H. nymphoides was 81.79% higher than that of I. tectorum. The PNUE ranged from 42.53±8.42 （I. tectorum） to 655.8±100.93 （Angelonia angustifolia） among the plant species. Although there were high PNUE values in Canna indica, H. nymphoides, Cyperus involucratus,and Typha orientalis, the interspecific differences were not significance （P 〉 0.05）. The PNUE of these plant species were, however, significantly higher than those of plant species with lower PNUE （including Acorus calamus, Ruellia brittoniana, and I. tectorum, P 〈 0.05）. The interspecific correlation between PNUE and Psat （mass-based, μmol kg-1s-1） versus SLA was significantly positive, whereas in contrast, the correlation between SLA and Psat （area-based, μmol m-2s-1） versus TN （area-based, mmol/m2） was significantly negative （P 〈 0.05）. The PNUE, SLA, Psat, and TN values of the exotic plant group were all significantly higher than those of the indigenous plant group （T-test, P 〈 0.05）. Overall, these results suggest that the exotic aquatic plant species may use resources more efficiently in eutrophied habitats, and have potentially higher growth rates and advantages in interspecific competition.