Effects of Phosphate Shortage on Root Growth and Hormone Content of Barley Depend on Capacity of the Roots to Accumulate ABA

Abstract

Although changes in root architecture in response to the environment can optimize mineral and water nutrient uptake, mechanisms regulating these changes are not well-understood. We investigated whether P deprivation effects on root development are mediated by abscisic acid (ABA) and its interactions with other hormones. The ABA-deficient barley mutant Az34 and its wild-type (WT) were grown in P-deprived and P-replete conditions, and hormones were measured in whole roots and root tips. Although P deprivation decreased growth in shoot mass similarly in both genotypes, only the WT increased primary root length and number of lateral roots. The effect was accompanied by ABA accumulation in root tips, a response not seen in Az34. Increased ABA in P-deprived WT was accompanied by decreased concentrations of cytokinin, an inhibitor of root extension. Furthermore, P-deficiency in the WT increased auxin concentration in whole root systems in association with increased root branching. In the ABA-deficient mutant, P-starvation failed to stimulate root elongation or promote branching, and there was no decline in cytokinin and no increase in auxin. The results demonstrate ABA’s ability to mediate in root growth responses to P starvation in barley, an effect linked to its effects on cytokinin and auxin concentrations.

Influence of Hydrocarbon-Oxidizing Bacteria on the Growth, Biochemical Characteristics, and Hormonal Status of Barley Plants and the Content of Petroleum Hydrocarbons in the Soil

“…However, less attention was paid to the hormonal status of plants growing in oil-contaminated soil. Reports on this theme are scarce and corresponding experiments have been performed in laboratories [ 15 , 37 ]. In the present field experiment, the effect of oil pollution on the hormonal system of barley plants was manifested in an increase in the IAA level in the shoots and a decrease in its content in the roots ( Figure 4 a,b).…”

“…Purification and analysis of cytokinins (zeatin, its riboside, and nucleotide) were performed according to [ 76 ]. The hormone content was determined by ELISA using the appropriate antibodies [ 37 ].…”

Association of Barley Root Elongation with ABA-Dependent Transport of Cytokinins from Roots and Shoots under Supra-Optimal Concentrations of Nitrates and Phosphates

“…Deficiency of nitrates and phosphates both influenced the expression of the IPT genes [11] and the content of cytokinins in plants [12], involving these hormones in the response of plants to P deficiency. The most attention has been paid to the transport of cytokinins from roots to shoots, acting as a long-distance signal that controls shoot function in response to the availability of nutrients (see the review of Kudoyarova et al [13] and references therein).…”

“…The involvement of hormones in the growth reaction of the roots attracted less attention. Nevertheless, the decline in root cytokinin of P-and Nstarved plants was accompanied by acceleration of root growth [11,12,14]. Since cytokinins can inhibit root elongation [15], a decrease in their content was considered as the cause of accelerated root growth in response to deficiencies in mineral nutrients [16].…”

“…Cytokinins and abscisic acid (ABA) are both involved in responses to the availability of mineral nutrients. Experiments with wheat plants treated with fluridone (inhibitor of ABA synthesis) and ABA-deficient barley plants showed that changes in cytokinin concentration in response to the shortage of mineral nutrients depended on the ability of plants to accumulate ABA [11,16]. However, interaction of ABA and cytokinins in response to long-term action of supra-optimal concentrations of mineral nutrients has not been studied.…”