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作 者 ：王文杰,祖元刚*,陈华峰,张衷华,杨逢建,赵则海,曹建国

期 刊 ：生态学报 2008年 28卷 9期 页码：4088~4098

关键词：薇甘菊(Mikania micrantha)；光合速率；呼吸速率；蒸腾速率；气孔导度；频率分布；种间比较；

Keywords:Gas exchange characteristics of the harmful forest weed Mikania micrantha,

摘 要 ：通过对不同条件和状态下的薇甘菊叶片光合能力（Pn）、呼吸（R）、气孔导度（gs）、蒸腾（Tr）、羧化效率（CE）、最大表观量子效率（）及水分利用效率（WUE）进行大量测定，并与同一地区（群落）其它对照种进行对比研究，发现薇甘菊具有以下特征：（1）薇甘菊叶片CO2和水分交换参数在上述不同条件下变化范围达数倍至十几倍，显示其强可塑性。种间比较发现，营养及生殖生长季内薇甘菊Pn与当地木本植物相当，稍低于其它藤本植物，远低于草本植物，说明薇甘菊的强入侵能力可能并非依靠单位叶片的强光合能力，而是其它因素，如前所述光合作用在不同生境、不同生长状态下的光合可塑性等；（2）林下生长薇甘菊的光合能力低于林间空地，而林间空地薇甘菊低于林缘（外）生境。对照实验也证明阴生生境薇甘菊光合显著低于阳生生境。说明薇甘菊是强阳性植物，与其它因子（水分）相比，光照条件是影响其光合能力的最重要因素，可以通过改变林分群落结构、增大郁闭度等降低光照措施来进行生态防治； （3）综合所有室内和野外数据进行频率分析发现，各指标均呈现（偏）正态分布。其中Pn集中分布区在2~10 μmol?m-2s-1之间（占所测总数据的70%）；gs集中分布在0.05~0.45 mol?m-2s-1之间（73%）；Tr的集中分布区为1~5 mmol?m-2s-1（66%）；CE分布于0.01~0.05 mol?mol-1之间数据占64%；近半的R分布在集中区域0.5~1.5 μmol?m-2s-1之间，而在0.5~2.5μmol?m-2s-1之间的数据占所测总量的66%；的集中分布区在0.04~ 0.08 mol?mol-1之间（77%）；这些数据为种间比较等统计分析比较工作奠定统计基础； （4）薇甘菊叶片对Pn和WUE的调节具有类似的方式，即光合作用最主要的调节因素是CE，其次是gs，而与的相关不显著；WUE主要是由Pn大小控制，Tr的影响相对较小，薇甘菊叶片WUE随gs的变化而保持恒定。上述有关薇甘菊的CO2和水分交换特性的研究，可以为这一入侵物种的防治提供基础数据支撑。

Abstract:The net photosynthetic capacity (Pn), respiration rate (R), stomatal conductance (gs), transpiration rate (Tr), carboxylation efficiency (CE), maximum apparent quantum yield () and photosynthetic water use efficiency (WUE) of Mikania micrantha was measured under different conditions. These included a variety of habitats, different leaf sizes, leaf ages and leaf orders, decumbent or climbing habits, presence or absence of parasitism by Cuscuta campestris, and was carried out in both the vegetative (summer) and reproductive (winter) seasons. Further comparisons with other herbaceous, woody and liane species in the same region (during the vegetative season) or population (in the reproductive season) were also carried out. The following conclusions were drawn from the results. (1) Under diverse conditions, parameters of CO2 and H2O exchange by M. micrantha varied from several-fold to ten-fold, thus showing large plasticity in acclimatizing to different microenvironments. On average, the Pn of M. micrantha in both the vegetative and reproductive seasons was equivalent to that of the woody species in the same region or population was slightly lower than in liane species, and much lower than in herbs. This finding indicates that the strong invasive ability of this weed might not be related to the photosynthetic capacity per leaf area, but rather may be due to other mechanisms such as its strong ability to acclimatize to different habitats on account of its photosynthetic plasticity. (2) The photosynthetic capacity of M. micrantha on the forest floor was much lower than that in the glade, while plants on the forest margin had the highest Pn. Moreover, a contrasting experiment also demonstrated that M. micrantha plants growing in shady sites photosynthesized at a much lower rate than plants in sunny sites. These results reflect the ecological characteristics of this weed and that it demands strong light for vigorous growth. Thus, reducing light infiltration through the modification of forest structure as well as increasing crown density should be an effective ecological method for controlling this weed. (3) Data (whole data in present paper) statistics showed that Pn of this weed centralized in the range of 2-10 μmol m-2 s-1 (70% of total data), gs in the range of 0.05-0.45 mol m-2 s-1 (73%), Tr in the range of 1-5 mmol m-2 s-1 (66%). About 64% of total CE was in the range of 0.01-0.05mol.mol-1. Near half R was in the range of 0.5-1.5 μmol m-2s-1, while 66% of the data was in the range of 05-2.5 μmol m-2s-1.The distribution center of (77%) was 0.04-0.08 mol.mol-1. These frequency distribution analyses reflect all measured data is in a normal or bias-normal distribution and these data made it possible for inter-species comparison on a statistical base. (4) Similar regulating mechanisms on Pn and WUE of this weed were found in different habitats, leaf ages, and growth status. Pn was mainly regulated by CE and secondly by gs, but no significant correlation was found between  and Pn. WUE was mainly controlled by Pn, while Tr made a relatively low contribution. The WUE was maintained at a constant level with changes in gs. Overall, the data of gas exchanges in this paper of this weed may strengthen the base for controlling the invasion of this species.

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