Murphy Lesley R, Barroca João, Franceschi Vincent R, Lee Raymond, Roalson Eric H, Edwards Gerald E, Ku Maurice S B
School of Biological Sciences and Center for Integrated Biotechnology, Washington State University, Pullman, WA 99164-4236, USA.
Institute of Agricultural Biotechnology, National Chiayi University, Chiayi 60004, Taiwan.
Funct Plant Biol. 2007 Aug;34(7):571-580. doi: 10.1071/FP06296.
Eleocharis contains many amphibious species, and displays diversity of photosynthetic mechanism (C C or C-C intermediates). A unique feature of Eleocharis is the plasticity in the photosynthetic mechanism of some species in response to the environment. In this study, we have examined the culm anatomy and photosynthetic property of several Eleocharis species grown terrestrially and the changes in the newly produced culms over a short period time frame after switching from terrestrial to submerged condition. Eleocharis baldwinii (Torrey) Chapman is C-like in terrestrial habitat, exhibiting O inhibition of photosynthesis with Rubisco expressed in both mesophyll and bundle sheath cells and PEPC strictly in the mesophyll cells, but switches to C-C intermediacy when submerged. In addition to Eleocharis vivipara Link type 1 (which switches from C-like to C), two other photosynthetic types examined in this study were shown to have different responses to growth in either terrestrial or submerged conditions. E. vivipara type 2 is a typical C plant in the terrestrial habitat, but becomes a C-C intermediate under submerged conditions. Further, terrestrially, E. vivipara type 3 is a C-C intermediate, but when submerged the δC value increases to -6.7‰, indicating its use of bicarbonate as a major carbon source. The submerged form of this plant exhibited about three times higher photosynthetic O evolution rate, compared to the C species Eleocharis erythropoda Steudel. These Eleocharis species possess different molecular switches for regulating C gene expression in response to environmental stimuli both between different species, and in E. vivipara among different populations. The apparent expression of a bicarbonate transport system by E. vivipara type 3 while submerged represents a unique adaptation to low CO availability.
荸荠属包含许多两栖物种，并且展现出光合机制（C₃、C₄或C₃ - C₄中间类型）的多样性。荸荠属的一个独特特征是一些物种的光合机制会根据环境产生可塑性变化。在本研究中，我们研究了几种在陆地生长的荸荠属物种的茎解剖结构和光合特性，以及从陆地条件转换到淹没条件后短时间内新生成茎的变化。鲍德温荸荠（Eleocharis baldwinii (Torrey) Chapman）在陆地生境中类似C₃植物，光合作用表现出对氧气的抑制，叶肉细胞和维管束鞘细胞中均有核酮糖-1,5-二磷酸羧化酶（Rubisco）表达，叶肉细胞中严格有磷酸烯醇式丙酮酸羧化酶（PEPC）表达，但淹没时转变为C₃ - C₄中间类型。除了胎生荸荠（Eleocharis vivipara Link）1型（从类似C₃转变为C₄），本研究中检测的另外两种光合类型对陆地或淹没条件下的生长表现出不同反应。胎生荸荠2型在陆地生境中是典型的C₄植物，但在淹没条件下变为C₃ - C₄中间类型。此外，在陆地上，胎生荸荠3型是C₃ - C₄中间类型，但淹没时δ¹³C值增加到 - 6.7‰，表明其以碳酸氢盐作为主要碳源。与C₃物种红褐荸荠（Eleocharis erythropoda Steudel）相比，该植物的淹没形态光合放氧速率高出约三倍。这些荸荠属物种在不同物种之间以及胎生荸荠不同种群之间，拥有不同的分子开关来响应环境刺激调节C₄基因表达。胎生荸荠3型在淹没时明显表达碳酸氢盐转运系统，这代表了对低二氧化碳可利用性的独特适应。
