Exogenously-Sourced Ethylene Modulates Defense Mechanisms and Promotes Tolerance to Zinc Stress in Mustard (Brassica juncea L.)

Abstract

Heavy metal (HM) contamination of agricultural soil is primarily related to anthropogenic perturbations. Exposure to high concentration of HMs causes toxicity and undesirable effects in plants. In this study, the significance of ethylene was studied in response of mustard (Brassica juncea) to a high level (200 mg kg−1 soil) of zinc (Zn) exposure. Plants with high Zn showed inhibited photosynthesis and growth with the increase in oxidative stress. Application of ethylene (as ethephon) to Zn-grown plants restored photosynthesis and growth by inhibiting oxidative stress through increased antioxidant activity, the proline metabolism glyoxalase system, and nutrient homoeostasis. The results suggested that ethylene played a role in modulating defense mechanisms for tolerance of plants to Zn stress.

Ethylene and Sulfur Coordinately Modulate the Antioxidant System and ABA Accumulation in Mustard Plants under Salt Stress

“…Indeed, it has been reported that ethephon at 50 and 100 ppm increased protein band intensities compared to untreated plants of broad bean [ 62 ]. The higher leaf area observed ( Table 5 ) was likely correlated with ethephon-enhanced ethylene biosynthesis ( Figure 1 ), as also found in other studies [ 45 , 47 ].…”

“…Ethylene plays a role in regulating synthesis of S compounds and controls plant processes and stress tolerance [ 19 , 47 ]. It has been reported that ethylene interacts with Se and improves the antioxidant system under Cd stress by inducing defense responses [ 48 , 49 ].…”

“…Ethylene-mediated variation in stomatal response [ 52 , 53 , 54 ] has been shown to influence photosynthesis [ 47 ]. Under salt stress, stomatal closing occurred, likely because of the phytotoxic effect of salt.…”

“…The influence of S on photosynthetic characteristics is well recognized as a virtue of stabilization of enzyme protein structure [ 4 ]. Ethephon application has been shown to increase photosynthesis through increased use efficiency of nutrients, stomatal conductance and Rubisco activity [ 45 , 47 ]. It has been reported that ethylene signaling is required for salt-tolerance as ethylene insensitive mutant showed more salt sensitivity [ 58 ].…”

Abiotic Stress Tolerance in Crop Plants: Role of Phytohormones

“…The results after 30 DAS revealed that exposure to Zn stress causes toxicity by inhibiting photosynthesis and growth, while increasing the oxidative stress biomarkers. ET application (as ethephon) to Zn-stressed plants restored photosynthesis and growth of mustard plants by decreasing oxidative stress via augmenting antioxidant activity, the metabolism of proline, glyoxalase system, and optimum nutrient homoeostasis [89]. In tomato plants, Alves et al [90] provided new insights into the interactive role of ET on selenium-mediated antioxidant enzymes under Cd stress.…”