title: A Potential Role of Flag Leaf Potassium in Conferring Tolerance to Drought-Induced Leaf Senescence in Barley.
abstract: Terminal drought stress decreases crop yields by inducing abscisic acid (ABA) and premature leaf senescence. As potassium (K) is known to interfere with ABA homeostasis we addressed the question whether there is genetic variability regarding the role of K nutrition in ABA homeostasis and drought tolerance. To compare their response to drought stress, two barley lines contrasting in drought-induced leaf senescence were grown in a pot experiment under high and low K supply for the analysis of flag leaves from the same developmental stage. Relative to the drought-sensitive line LPR, the line HPR retained more K in its flag leaves under low K supply and showed delayed flag leaf senescence under terminal drought stress. High K retention was further associated with a higher leaf water status, a higher concentration of starch and other primary carbon metabolites. With regard to ABA homeostasis, HPR accumulated less ABA but higher levels of the ABA degradation products phaseic acid (PA) and dehydro-PA. Under K deficiency this went along with higher transcript levels of ABA8'-HYDROXYLASE, encoding a key enzyme in ABA degradation. The present study provides evidence for a positive impact of the K nutritional status on ABA homeostasis and carbohydrate metabolism under drought stress. We conclude that genotypes with a high K nutritional status in the flag leaf show superior drought tolerance by promoting ABA degradation but attenuating starch degradation which delays flag leaf senescence. Flag leaf K levels may thus represent a useful trait for the selection of drought-tolerant barley cultivars.
authors.affiliation: Molecular Plant Nutrition Group, Physiology and Cell Biology, Leibniz-Institute of Plant Genetics and Crop Plant Research Gatersleben, Germany.
authors.forename: Seyed A
authors.initials: SA
authors.lastname: Hosseini
authors.affiliation: Molecular Plant Nutrition Group, Physiology and Cell Biology, Leibniz-Institute of Plant Genetics and Crop Plant Research Gatersleben, Germany.
authors.forename: Mohammad R
authors.initials: MR
authors.lastname: Hajirezaei
authors.affiliation: Abiotic Stress Genomics Group, Molecular Genetics, Leibniz-Institute of Plant Genetics and Crop Plant Research Gatersleben, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Seiler
authors.affiliation: Abiotic Stress Genomics Group, Molecular Genetics, Leibniz-Institute of Plant Genetics and Crop Plant Research Gatersleben, Germany.
authors.forename: Nese
authors.initials: N
authors.lastname: Sreenivasulu
authors.affiliation: Molecular Plant Nutrition Group, Physiology and Cell Biology, Leibniz-Institute of Plant Genetics and Crop Plant Research Gatersleben, Germany.
authors.forename: Nicolaus
authors.initials: N
authors.lastname: von Wirén
keywords: ABA homeostasis; drought stress tolerance; potassium efficiency; primary metabolites; starch metabolism