24-Epibrassinolide regulates photosynthesis, antioxidant enzyme activities and proline content of Cucumis sativus under salt and/or copper stress

Abstract

Brassinosteroids have been extensively used to overcome various abiotic stresses. But its role in combined stress of salt and excess copper remains unexplored. Seeds of two cultivars (Rocket and Jumbo) of Cucumis sativus were grown in sand amended with copper (100 mg kg(-1)), and developed seedlings were exposed to salt stress in the form of NaCl (150 mM) at the 30-day stage of growth for 3 days. These seedlings were subsequently sprayed with 0 or 0.01 μM of 24-epibrassinolide (EBL) at the 35-day stage. The plants exposed to NaCl and Cu in combination exhibited a significant decline in fresh and dry mass of plant, chlorophyll content, activities of carbonic anhydrase, net photosynthetic rate and maximum quantum yield of the PSII primary photochemistry followed by NaCl and Cu stress alone, more severely in Jumbo than in Rocket. However, the follow-up treatment with EBL to the stressed and nonstressed plant improved growth, chlorophyll content, carbonic anhydrase activity and photosynthetic efficiency, and further enhanced the activity of various antioxidant enzymes viz. catalase, peroxidase and superoxide dismutase and content of proline at the 40-day stage of growth, and the response of the hormone was more effective in Rocket than in Jumbo. The elevated level of antioxidant enzymes as well as proline could have conferred tolerance to the NaCl- and/or Cu-stressed plants resulting in improved growth, water relations and photosynthetic attributes. Furthermore, antioxidant enzyme activity and proline content were more enhanced in Rocket than in Jumbo cultivar.

Copper (Cu) stress affects carbon and antioxidant metabolism in Coffea arabica seedlings

“…2C and 2D). Similar results were found in Cucumis sativus (Fariduddin et al, 2013), where proline levels were substantially increased as a result of copper deficiency. The decrease in proline levels may be due to degradation reactions of this amino acid, which are catalyzed by mitochondrial enzymes such as proline dehydrogenase in various stress conditions (Pavlikova et al, 2008;Kavi-Kishor et al, 1995).…”

Participation of Phytohormones in Adaptation to Salt Stress

“…Besides the participation in plant physiology, e.g., plant development, cell division, and cell elongation in stems or roots, brassinosteroids are active in stress responses (Ahammed et al 2015 ;Fariduddin et al 2013 ).…”

Efficiency index as the integral indicator of Triticum aestivum response to growth regulators

“…Thus, under the stress effect of metals, the effectiveness of brassinosteroids was evaluated according to the following indices (for different species): in Indian mustard and common radish it was assessed by the activity of enzymes of radical scavenging system, plants growth and nickel (Ni) accumulation (Choudhary et al, 2011;Kanwar et al, 2013); in cucumber -by biomass accumulation, the content of chlorophyll and the activity of carbonic anhydrase (Fariduddin et al, 2013); in common radish -by the activity of 6 antioxidant defense system enzymes, lipid peroxidation (LPO) intensity and by proline content (Sharma et al, 2011); in wheat -by grain yield and heavy metals accumulation in aerial biomass (Kroutil et al, 2010).…”

“…There are researches comparing several types of PGR that are close to the mode of action (StoynovaBakalova, Petrov, 2010;Choudhary et al, 2011), the effectiveness of several concentrations of the PGR (Gangwar et al, 2011), different exposure times (treatment times) with the PGR (Canakci, Dursun, 2011), the effectiveness of PGR in plants under several types of environmental stress (Fariduddin et al, 2013) or the effectiveness of PGR on several species/genotypes (Ali et al, 2015).…”