Macrophytes in the genus Ottelia are widely distributed from the tropics to the temperate regions including about 21 species worldwide, which can grow in a localized and relatively stable karst freshwater. The Ottelia genus plants were featured in this study for their broad leaves which for this reason may produce specialized functions that differed from other submerged species. However, there is limited knowledge about all the extant Ottelia species and varieties in China except for the well-studied O. alismoides, especially in related research on leaves. 

To explore the potential ecological role of Ottelia, supervised by associate Prof. JIANG Hongsheng and CAO Yu, PhD students LIU Yang and Ndirangu Leah of Wuhan Botanical Garden, conducted a field investigation on leaf traits in eight populations of Ottelia ranging from the southwestern Yunnan–Guizhou plateau to the southern Hainan Island in China. 

The different populations showed distinct functional traits of mature leaves; the leaf acidity at dawn and dusk was the highest in O. cordata, the leaf pigment content was the highest in O. acuminata var. jingxiensis, and O. acuminata var. songmingensis had the thickest and longest leaf with CaCO₃ precipitation on both sides of the leaf. In this study, the physiological traits were less sensitively divergent than morphological ones (seven clusters) among the eight populations. 

This study suggests that Ottelia populations play a significant role in carbon cycling as the dominant species in karst freshwaters in China. Furthermore, based on 24 leaf traits, the research has provided a quantitative profile of the eight Ottelia populations in the field.  

In addition, this is the first attempt to systematically analyze the leaf functional traits in submerged freshwater macrophytes. Therefore, more attention should be paid to the role of Ottelia populations on the carbon cycles in the karst freshwaters.  

The work was supported by the Strategic Priority Research Program of Chinese Academy of Sciences and the National Natural Science Foundation of China. Relevant research results have been published in Frontiers in Plant Science entitled “The Analysis of Leaf Traits of Eight Ottelia Populations and Their Potential Ecosystem Functions in Karst Freshwaters in China”. 

The cluster analysis of leaf traits of morphology and biomass in the eight populations. Leaf length and width is with the unit of cm, area with the unit of cm² and thickness with the unit of mm (Image by WBG)