Abstract

Gibberellic acid (GA) and jasmonic acid (JA) are considered to be endogenous regulators that play a vital role in regulating plant responses to stress conditions. This study investigated the ameliorative role of GA, JA, and the GA + JA mixture in mitigating the detrimental effect of salinity on the summer squash plant. In order to explore the physiological mechanisms of salt stress alleviation carried out by exogenous GA and JA, seed priming with 1.5 mM GA, 0.005 mM JA, and their mixture was performed; then the germinated summer squash seedlings were exposed to 50 mM NaCl. The results showed that a 50 mM NaCl treatment significantly reduced shoot and root fresh and dry weight, water content (%), the concentration of carotenoid (Car), nucleic acids, K+, and Mg++, the K+/Na+ ratio, and the activity of catalase (CAT) and ascorbate peroxidase (APX), while it increased the concentration of proline, thiobarbituric acid reactive substances (TBARS), Na+, and Cl− in summer squash plants, when compared with the control. However, seed priming with GA, JA and the GA + JA mixture significantly improved summer squash salt tolerance by reducing the concentration of Na+ and Cl−, TBARS, and the Chl a/b ratio and by increasing the activity of superoxide dismutase, CAT, and APX, the quantities of K+ and Mg++, the K+/Na+ ratio, and the quantities of RNA, DNA, chlorophyll b, and Car, which, in turn, ameliorated the growth of salinized plants. These findings suggest that GA and JA are able to efficiently defend summer squash plants from salinity destruction by adjusting nutrient uptake and increasing the activity of antioxidant enzymes in order to decrease reactive oxygen species accumulation due to salinity stress; these findings offer a practical intervention for summer squash cultivation in salt-affected soils. Synergistic effects of the GA and JA combination were not clearly observed, and JA alleviated most of the studied traits associated with salinity stress induced in summer squash more efficiently than GA or the GA + JA mixture.

Highlights

  • Salinity stress results in extensive crop damage worldwide; most field crops are salt sensitive, and the problem is expected to increase in the coming decades [1]

  • The Gibberellic acid (GA) and jasmonic acid (JA) combination showed antagonistic effects for the regulation of plant growth and for tolerance responses, while JA treatment alleviated salinity stress induced in summer squash more efficiently than GA treatment or the GA + JA combination

  • This study compares the effects of exogenous GA and JA on summer squash growth and metabolic responses to figure out which phytohormone is more efficient in alleviating salinity stress in this plant

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Summary

Introduction

Salinity stress results in extensive crop damage worldwide; most field crops are salt sensitive, and the problem is expected to increase in the coming decades [1]. Salinity is regarded as the most limiting and damaging of the factors that restrict crop growth, yield, and productivity [2]. Abscisic acid (ABA), gibberellins, ethylene, salicylic acid (SA), and jasmonic acid (JA) seem to be critical modules of complex signaling networks and have been integrated into current models of stress response [9]. They play an important role in prompting plant tolerance to various stress conditions

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