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.
Highlights
Drought is one of the most serious environmental stresses limiting crop growth and productivity worldwide (Huang et al, 2014)
In order to determine whether drought-induced leaf senescence is modulated by the K nutritional status, we cultivated two barley lines, which differ in senescence behavior under drought stress, at two K regimes and exposed them to terminal drought stress at flowering
Based on the comparison of two barley lines that differ in drought-induced leaf senescence, we tackled the question whether and to what extent genotypic differences in drought tolerance are related to the K nutritional status in leaves
Summary
Drought is one of the most serious environmental stresses limiting crop growth and productivity worldwide (Huang et al, 2014). Flag Leaf Potassium and Drought Tolerance occurs during the vegetative growth phase, the stress is mostly transient and holds on until rainfall comes back and restores plant growth This is typical for pre-summer drought periods, which are seen more and more in the continental climates of middle Europe. Occurrence of drought during generative plant development, i.e., around flowering, may induce premature leaf senescence that leads to a decline in photosynthesis and assimilate allocation, causing acceleration of the whole-plant maturation process (Gan, 2003) Under such terminal drought crop yields are mostly restricted by plant reproductive failure, followed by a shortening of the grain filling period which reduces grain number and grain size (Sreenivasulu et al, 2007)
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