Root yield, antioxidant capacities, and hormone contents in different drought-tolerant sweet potato cultivars treated with ABA under early drought stress

Abstract

The current work is aimed at assessing the impact of abscisic acid (ABA) on the resistance of two drought contrasting sweet potato cultivars, namely, Jishu 21 (J21, tolerant) and Jizishu 1 (JZ1, sensitive), to early drought stress (DS). Each cultivar was subjected to three treatments as follows: control, well-watered; early DS + foliar application of distilled water; early DS + foliar application of 150 μmol L−1 ABA. Results showed that early DS caused osmotic stress injury both in leaves and fibrous roots (FR). Under DS, J21 exhibited lower relative electrical conductivity (REC) in the leaves, and malondialdehyde (MDA) content in both the leaves and FR, increased contents of soluble sugar (SS) and free amino acids (FAA), and elevated activities of catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX) in the leaves and FR, compared with JZ1. In the leaves, ABA application at early DS increased the leaf area index (LAI), the relative water content (RWC), the contents of chlorophyll (Chl), SS, proline (Pro), gibberellic acid-3 (GA3), and indole-3-acetic acid (IAA), and the activities of CAT, SOD, peroxidase (POD), and APX but lowered the REC and MDA content at all sampling days. ABA also increased the contents of zeatin riboside (ZR) and ABA on the 60th and 80th day after planting (DAP). In the FR, ABA application at early DS increased the FAA and Pro contents and the rate of reaction of CAT, SOD, and APX but lowered the MDA levels. Additionally, ABA application on JZ1 caused a higher increase in the percentage of some parameters both in the leaves and FR relative to J21 and JZ1 cultivar was more sensitive to the ABA treatment.