Work

Combined heat and salinity stress accelerates oxidative injury and ABA-mediated stress response in cucumber seedlings

Year: 2026

Type: article

Abstract: Introduction: Cucumber is a heat- and salt-stress-sensitive vegetable crop, whose productivity and marketability are endangered by increasing temperatures and soil salinization driven by climate change. Combined stresses are becoming frequent, yet their interactive effects remain poorly understood. Methodology: The current study evaluated the negative impacts of high temperature (HT, 40 °C) and salinity (75 and 150 mM NaCl) alone and in combination on cucumber seedlings, under a triplicated completely randomized design. Standard plant growth parameters, micro- and macronutrients, phytohormones, photosynthetic pigment concentrations, oxidative stress biomarkers, osmo-protectants, and antioxidant enzymes were recorded. Results: ion concentrations compared to 150 mM NaCl stress alone. Reduced plant growth under combined heat-salinity stress was associated with pronounced disturbances in mineral nutrition and ion homeostasis, although the relative contributions of nutrient imbalance and ionic toxicity could not be distinguished based on tissue mineral concentrations alone. Moreover, plant growth reprogramming toward survival rather than growth was observed with a 206-fold increase in abscisic acid (ABA) and ~99% decline in indole acetic acid, gibberellic acid, and zeatin. Intensified oxidative stress stimulated coordinated activation of ROS (reactive oxygen species) scavenging enzymes, and glutathione-dependent redox metabolism (glucose-6-phosphate dehydrogenase, glutathione reductase, 6-phosphogluconate dehydrogenase, and glutathione-S-transferase increased by 36-, 38-, 41- and 54-fold, respectively), but these remained insufficient to prevent oxidative damage. However, HT and salinity stress triggered distinct pathways: HT preferentially promoted hydrogen peroxide accumulation and activated antioxidant defenses, while salt stress caused greater damage through membrane lipid peroxidation along with ionic imbalance. Conclusion: These findings suggest that salinity primarily caused physiological impairment, whereas HT amplified oxidative signaling and antioxidant metabolism, providing new insights and potential targets for developing cucumber cultivars with enhanced tolerance to combined stresses. Future research should integrate multi-omics technologies with functional genomics to study the molecular networks regulating nutrient homeostasis, antioxidant metabolism, and ABA signaling under combined stress.

Source: Frontiers in Plant Science

DOI: 10.3389/fpls.2026.1963962