Paclobutrazol Modulates Physiological and Hormonal Changes in Amorpha fruticosa under Drought Stress

Abstract

Improving the drought resistance of slope-protecting plants offer a promising strategy to slope protection where water capacity is low and temperature and moisture change drastically. To study the mechanism of paclobutrazol in improving the drought resistance, six different concentrations of paclobutrazol (0, 10, 50, 100, 150 and 200 mg/L) were applied in Amorpha fruticosa L. seedlings and after a month drought stress was induced by withholding water irrigation for 15 days. Three levels of relative water contents, 75–80% (well-watered), 55–60% (mild drought stress), and 35–40% (severe drought stress), were used. The water content of A. fruticosa treated without paclobutrazol was kept at 75–80% as control, and the water content was replenished by weighing method. During these three periods, the changes of morphology, physiology and hormonal contents were analyzed. The results showed that water stress reduced height, while paclobutrazol enhanced height relative growth rate under drought stress. Water stress induced peroxidase and soluble sugars, paclobutrazol made the effect to be more pronounced. Water deficit reduced chlorophyll and relative water content, but increased MDA content, the opposite results occurred when paclobutrazol were applied. Moreover, the contents of ABA, GA1 + 3, IAA, and ZR were higher in relation to water stress and paclobutrazol treatments. These indicates that paclobutrazol induced many adaptations (improving the relative growth rate in height, peroxidase activity, contents of soluble sugars, relative water content and chlorophyll, decreasing MDA content, and enhancing ABA, GA1 + 3, IAA, and ZR contents). Paclobutrazol with a concentration of 150 mg/L was found to be the optimum.