The Protective Role of 28-Homobrassinolide and Glomus versiforme in Cucumber to Withstand Saline Stress

Abstract

The strategic role of phytohormones and arbuscular mycorrhizal fungi (AMF) to overcome various stress conditions is gaining popularity in sustainable agricultural practices. This current study aims to investigate and identify the protective roles of 28-homobrassinolide (HBL) and Glomus versiforme on two cucumber cultivars (salt sensitive Jinyou 1# and tolerant Chanchun mici (CCMC)) grown under saline conditions (100 mM NaCl). HBL and AMF were applied as individual and combined treatments on two cucumber cultivars and their effects were observed on the morphological growth and physiology under control and saline conditions. Findings revealed that the treated plants showed better performance under saline conditions through improved photosynthesis, leaf relative water content, and decreased electrolyte leakage in tolerant cultivar (CCMC) and to a lesser extent in sensitive (Jinyou 1#) cultivar. Comparable differences were noticed in the antioxidant enzymes activity such as superoxide dismutase, catalase, and peroxidase after every 10 days in both cultivars. Treating the plants with HBL and AMF also improved the mineral uptake regulation and lowered sodium concentration in roots compared to that in the non-treated plants. Current findings suggest that the protective role of HBL and AMF involves the regulation of antioxidants and lowers the risk of ion toxicity in the cucumber and hence enhance tolerance to salinity. These results are promising, but further studies are needed to verify the crop tolerance to stress and help in sustainable agricultural production, particularly vegetables that are prone to salinity.

Keywords: 28-homobrassinolide; NaCl; antioxidant enzymes; arbuscular mycorrhizal fungi.

Figure 1

HBL, AMF, and their combination on NaCl (100 mM) induced changes on electrolyte leakage (EC %) and leaf relative water content (LRWC %) after 20 and 40 days (flowering and fruiting stage) of NaCl treatment on cucumber cultivars Jinyou 1# (salt sensitive) and CCMC (salt tolerant). Values presented for comparison are means of three replications in each treatment (±SE, standard error). Means followed by the same letters are not significantly different (p ≤ 0.05) according to the least significant difference (LSD) having three replications.

Figure 2

HBL, AMF, and their combination on the NaCl (100 mM) induced changes on photosynthesis (mmol CO₂ m⁻² S⁻¹), intercellular carbon dioxide concentration (µmol CO₂ m⁻² S⁻¹), stomatal conductance (mmol H2O m⁻² s⁻¹), and transpiration rate (mmol H₂O m⁻² s⁻¹) of cucumber cultivars (after 40 days NaCl treatment, fruiting stage), Jinyou 1# (salt sensitive) and CCMC (salt tolerant). Values presented for comparison are means of three replications in each treatment (±SE, standard error). Means followed by the same letters are not significantly different (p ≤ 0.05) according to the least significant difference (LSD) having three replications.

Figure 3

HBL, AMF, and their combination on the NaCl (100 mM) induced changes on colonization percentage (%) of AMF inoculum in roots of cucumber cultivars, Jinyou 1# (salt sensitive) and CCMC (salt tolerant). Colonization percentage was determined at the end of the experiment (after 40 days, fruiting stage). Values presented for comparison are means of three replications in each treatment (±SE, standard error). Values are means of at least three replications (±SE, standard error) presented for comparison. Means followed by the same letters are not significantly different (p ≤ 0.05) according to the least significant difference (LSD) having three replications.