Macrophytes live in extremely different carbon environments compared to terrestrial plants. In response to bicarbonate dominated inorganic carbon in natural aquatic systems, the ability for HCO₃⁻ use has been developed in many macrophytes to alleviate a limitation by CO₂ in aquatic systems. In the present study, all present macrophytes in a karst stream were investigated, and we found that seven of nine species were able to use HCO₃⁻ and two species at the source of the karst stream were restricted to CO₂ use. Two different inhibitors were used to determine the HCO₃⁻ use mechanisms in Ottelia guanyangensis and Vallisneria denseserrulata, the only species coexisting from up- to down-stream. External carbonic anhydrase (CAext) mediated HCO₃⁻ use was present in O. guanyangensis up-stream, and then O. guanyangensis shifted to a combined mechanism of CAext and anion exchange (AE) mediated HCO₃⁻ use down-stream. In these two species, high HCO₃⁻ concentration induced the ability to use HCO₃⁻, but high CO₂ concentration inhibited this ability. From up-stream to down-stream, the decreasing CO₂ induced increasing proportion of HCO₃⁻ use that led to changes in the δ¹³C in O. guanyangensis. However, a constant CAext and AE mediated HCO₃⁻ use caused a relatively stable δ¹³C in V. denseserrulata from river source to 330 m and then increased the proportion of HCO₃⁻ use at the stream outlet associated with the change in δ¹³C.

与陆地植物相比，大型植物生活在极为不同的碳环境中。响应于在天然水系统碳酸氢钠为主的无机碳，为HCO能力₃ ^-使用已开发在许多水生植物由CO，以减轻限制₂在水生系统。在本研究中，在岩溶溪流所有在场的水生植物进行了调查，我们发现，九七种能够使用HCO ₃ ^-和两个物种在岩溶流的来源仅限于CO ₂的使用。两种不同的抑制剂用于确定HCO ₃ ^-中使用的机制海菜花guanyangensis和Vallisneria densityserrulata，唯一从上游到下游共存的物种。外部碳酸酐酶（CAext）介导的HCO ₃ ^-使用在存在O. guanyangensis向上流，然后O. guanyangensis转移到介导的HCO CAext的组合机构和阴离子交换（AE）₃ ^-使用下游。在这两个物种，高HCO ₃ ^-浓度诱导使用HCO能力₃ ^- ，但高CO ₂浓度抑制这种能力。从向上流至下游，减小CO ₂引起的HCO的比例增加₃ ^-使用导致了δ变化¹³用C O. guanyangensis。然而，恒定CAext和AE介导的HCO ₃ ^-使用造成了相对稳定的δ ¹³用C V. denseserrulata从河流源至330微米，然后增加HCO比例₃ ^-在δ在与变化相关联的流出口用¹³ C。