Erratum.

Abstract

New Phytologist 227 (2020), 1749–1763, doi: 10.1111/nph.16644. Since its publication, the authors of Hu et al. have brought to our attention an error in the Discussion section of their article, where some text from the subsection ‘Redistribution of K contributes to incoordination of leaf area and photosynthetic rate’ is missing. The full paragraph from this subsection is given below. We apologize to our readers for this mistake. Discussion, subsection ‘Redistribution of K contributes to incoordination of leaf area and photosynthetic rate’ (p. 1760) Under different K-deficient stress, cell morphology and chloroplast density have been changed in succession, affecting cell investment and mesophyll CO2 conductance pathway (Fig. 7). That changes in S/W value that occurs earlier than changes in Sc/S and Dchl-chl regulated by leaf K concentration were the major cause of unequal reductions in leaf area and photosynthetic rate under K-deficient stress. Potassium is cationic, which is highly mobile in the plant; it is redistributed among the vacuole, cytosol, and chloroplasts under K deficiency stress. Potassium plays different roles in different organelles, such as maintaining ionic and pH homeostasis, ensuring osmotic balance for photosynthesis and metabolic processes in the cytosol and chloroplasts (Wu & Berkowitz, 1992; Song et al., 2004), and generating turgor in the vacuole (Ahmad et al., 2016). As the K concentration declines, K in organelles may be reduced or transferred. It has been reported that decreases of K content in the vacuole occurred earlier than those in the cytosol (Leigh & Wyn Jones, 1984; Jordan-Meille & Pellerin, 2008). Decreased K content in the vacuole will decrease cell turgor, affecting the extension of the cell wall, which regulates cell expansion and morphology (Van Volkenburgh, 1999). Osmotic balance controlled by K in chloroplasts is essential for chloroplast osmoregulation and integrity; and chloroplasts have higher K concentrations than the cytosol (Kunz et al., 2014). So, it can be speculated that the osmotic balance in chloroplasts cannot be maintained any more, when K content in the cytosol decreases. When the K concentration in dry matter is <1.5%, the K content in the cytosol is reduced (Leigh & Wyn Jones, 1984; Jordan-Meille & Pellerin, 2008). In this study, the distance between neighbouring chloroplasts increased rapidly when the K concentration in leaves dropped to <1.5% (Fig. 6). Deficiency of K in cytoplasm caused the reduction of chloroplast and changes of chloroplast morphology, inducing CO2 conductance resistance. A suitable method to quantify the flow of K between cell microdomains is essential for further understanding the regulation of mesophyll cell size and number, as well as chloroplast morphology.