Potassium Isotopes in Herbaceous Plants: A Potential New Tool for C<sub>3</sub> and C<sub>4</sub> Plant Research
Rui Qu, Guilin Han
Abstract
Abstract Plants play a critical role in the surficial environment, influencing energy transfer, the global carbon cycle, and climate change. Potassium (K) controls many essential plant physiological features like photosynthesis, cell osmosis adjustment, and enzyme activity. However, few plant species of K isotopes have been investigated and knowledge regarding the mechanism of isotopic fractionations in biological processes is still limited. This study investigated foliar K isotopic compositions of C 3 and C 4 vegetation and soil in the typical karst region of Guizhou Province, Southwest China. The results showed that: (a) The δ 41 K of soil ranged from −0.04‰ to −0.08‰, with no K isotope ratios change between topsoil and subsoil. (b) Foliar δ 41 K of C 3 vegetation ranged from −1.06 ± 0.06‰ to −0.15 ± 0.06‰ and foliar δ 41 K of C 4 vegetation varied from 0.28 ± 0.05‰ to 1.15 ± 0.06‰. (c) Foliar δ 41 K was negatively related to foliar K concentration ( R 2 = 0.78; p < 0.01); The significant K isotope differences between C 3 and C 4 vegetation are likely attributed to their different mechanisms for drought stress or their different foliar K concentration. This study firstly documented the potential of K isotopes as a novel tool for biological processes to distinguish between C 3 and C 4 plants and also shed light on the potential future application of K isotope signatures in soil‐plant interactions.