Wei Hu1, Taylor D Coomer2, Dimitra A Loka3, Derrick M Oosterhuis4, Zhiguo Zhou5. 1. College of Agriculture, Nanjing Agricultural University, Nanjing 210095, Jiangsu Province, PR China; Department of Crop, Soil, and Environmental Sciences, University of Arkansas, 1366 West Altheimer Drive, Fayetteville, AR 72704, USA. 2. Department of Crop, Soil, and Environmental Sciences, University of Arkansas, 1366 West Altheimer Drive, Fayetteville, AR 72704, USA. 3. Department of Crop, Soil, and Environmental Sciences, University of Arkansas, 1366 West Altheimer Drive, Fayetteville, AR 72704, USA; Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Ceredigion, UK. 4. Department of Crop, Soil, and Environmental Sciences, University of Arkansas, 1366 West Altheimer Drive, Fayetteville, AR 72704, USA. Electronic address: oosterhu@uark.edu. 5. College of Agriculture, Nanjing Agricultural University, Nanjing 210095, Jiangsu Province, PR China. Electronic address: giscott@njau.edu.cn.
Abstract
Potassium (K) plays important roles in the metabolism of carbon (C) and nitrogen (N), but studies of K deficiency affecting C-N balance are lacking. This study explored the influence of K deficiency on C-N interaction in cotton leaves by conducting a field experiment with cotton cultivar DP0912 under two K rates (K0: 0 kg K2O ha-1 and K67: 67 kg K2O ha-1) and a controlled environment experiment with K-deficient solution (K1: 0 mM K+) and K-sufficient solution (K2: 6 mM K+). The results showed that leaf K content, leaf number, leaf area, boll number, reproductive dry weight and total dry weight were significant lower under K deficiency (K0 or K1). Lower total chlorophyll content and Chl a/b ratio, and decreased Pn along with lower Gs and higher Ci were measured under K deficiency, suggesting that the decrease in Pn was resulted from non-stomatal limitation. Leaf glucose, fructose, sucrose and starch contents were higher under K deficiency, because lower sucrose export was detected in phloem. Although leaf nitrate and ammonium contents significantly decreased, free amino acid content was increased by 40-63% under K deficiency, since lower amino acid export was also measured in phloem. K deficiency also induced lower soluble protein content in leaves. Leaf ATP level was significantly increased under K deficiency, indicating ATP utilization was lower, so that less energy was supplied to C and N metabolism. The ratio of soluble sugar to free amino acid and the C/N ratio markedly increased under K deficiency, and one reason was that the phloem export reduced more prominent for sucrose (54.6-78.0%) than amino acid (36.7-85.4%) under K deficiency. In addition, lower phosphoenolpyruvate carboxylase activity limited malate and citrate biosynthesis under K deficiency, causing a decrease of C flux into the amino acids, which was not beneficial for maintaining C-N balance. Sucrose phosphate synthase and nitrate reductase activities were lower under K deficiency, which would limit sucrose biosynthesis and nitrate assimilation. This was another factor altering soluble sugar to free amino acid ratio and C/N ratio in the K-deficient leaves.
Potassium (K) plays important roles in the metabolism of n class="Chemical">carbon (C) and nitrogen (N), but studies of K deficiency affecting C-N balance are lacking. This study explored the influence of K deficiency on C-N interaction in cotton leaves by conducting a field experiment with cotton cultivar DP0912 under two K rates (K0: 0 kg K2Oha-1 and K67: 67 kg K2Oha-1) and a controlled environment experiment with K-deficient solution (K1: 0 mM K+) and K-sufficient solution (K2: 6 mM K+). The results showed that leaf K content, leaf number, leaf area, boll number, reproductive dry weight and total dry weight were significant lower under K deficiency (K0 or K1). Lower total chlorophyll content and Chl a/b ratio, and decreased Pn along with lower Gs and higher Ci were measured under K deficiency, suggesting that the decrease in Pn was resulted from non-stomatal limitation. Leaf glucose, fructose, sucrose and starch contents were higher under K deficiency, because lower sucrose export was detected in phloem. Although leaf nitrate and ammonium contents significantly decreased, free amino acid content was increased by 40-63% under K deficiency, since lower amino acid export was also measured in phloem. K deficiency also induced lower soluble protein content in leaves. Leaf ATP level was significantly increased under K deficiency, indicating ATP utilization was lower, so that less energy was supplied to C and N metabolism. The ratio of soluble sugar to free amino acid and the C/N ratio markedly increased under K deficiency, and one reason was that the phloem export reduced more prominent for sucrose (54.6-78.0%) than amino acid (36.7-85.4%) under K deficiency. In addition, lower phosphoenolpyruvate carboxylase activity limited malate and citrate biosynthesis under K deficiency, causing a decrease of C flux into the amino acids, which was not beneficial for maintaining C-N balance. Sucrose phosphate synthase and nitrate reductase activities were lower under K deficiency, which would limit sucrose biosynthesis and nitrate assimilation. This was another factor altering soluble sugar to free amino acid ratio and C/N ratio in the K-deficient leaves.
Authors: Servane Bigot; Paula Pongrac; Martin Šala; Johannes T van Elteren; Juan-Pablo Martínez; Stanley Lutts; Muriel Quinet Journal: Plants (Basel) Date: 2022-02-28