Cameron Duncan D, Preiss Katja, Gebauer Gerhard, Read David J
Department of Animal and Plant Sciences, University of Sheffield, Alfred Denny Building, Western Bank, Sheffield, S10 2TN, UK.
BayCEER - Laboratory of Isotope Biogeochemistry, University of Bayreuth Universitätsstrasse 30, D-95440 Bayreuth, Germany.
New Phytol. 2009;183(2):358-364. doi: 10.1111/j.1469-8137.2009.02853.x. Epub 2009 Apr 27.
While measurements of tissue stable isotope signatures and isotope mixing models have suggested that the green orchid Corallorhiza trifida is photosynthetically active and hence only partially mycoheterotrophic, these assumptions have not been validated by direct analysis of carbon assimilation. The photosynthetic capabilities of three orchid species assumed on the basis of the indirect methods or chlorophyll content to have differing trophic strategies: Neottia nidus-avis (fully mycoheterotrophic), Cephalanthera damasonium (partially autotrophic), C. trifida (partially autotrophic), as well as saplings of an autotrophic tree, Fagus sylvatica, were investigated by combining the determination of chlorophyll content and fluorescence, with direct measurement of the potential for CO(2) assimilation using (13)C isotope tracers in the field. Chlorophyll content and fluorescence values were indicative of ineffective photochemical processes in Neottia and reduced efficiency of photochemical processes in Corallorhiza. These differences are reflected in the mean assimilation rates of (13)CO(2) of 594 +/- 129, 331 +/- 72, 12.4 +/- 2.4 and 7.3 +/- 0.9 microg g(-1) h(-1) for Fagus, Cephalanthera, Corallorhiza and Neottia, respectively. Our study, while confirming the fully mycoheterotrophic status of Neottia and the partially autotrophic condition in Cephalanthera, also demonstrates under field conditions that Corallorhiza is physiologically closer to the fully mycoheterotrophic condition than has previously been recognized.
虽然对组织稳定同位素特征的测量和同位素混合模型表明，绿花珊瑚兰（Corallorhiza trifida）具有光合活性，因此只是部分菌根异养型，但这些假设尚未通过碳同化的直接分析得到验证。基于间接方法或叶绿素含量，假定三种具有不同营养策略的兰花物种的光合能力：鸟巢兰（Neottia nidus-avis，完全菌根异养型）、头蕊兰（Cephalanthera damasonium，部分自养型）、绿花珊瑚兰（部分自养型），以及一种自养树木欧洲水青冈（Fagus sylvatica）的树苗，通过结合叶绿素含量和荧光的测定，以及在田间使用¹³C同位素示踪剂直接测量CO₂同化潜力，对它们进行了研究。叶绿素含量和荧光值表明，鸟巢兰的光化学过程无效，而珊瑚兰的光化学过程效率降低。这些差异反映在欧洲水青冈、头蕊兰、珊瑚兰和鸟巢兰的¹³CO₂平均同化率上，分别为594±129、331±72、12.4±2.4和7.3±0.9微克克⁻¹小时⁻¹。我们的研究在确认鸟巢兰完全菌根异养状态和头蕊兰部分自养状态的同时，也表明在田间条件下，珊瑚兰在生理上比以前认为的更接近完全菌根异养状态。
