28-homobrassinolide improves growth and photosynthesis in Cucumis sativus L. through an enhanced antioxidant system in the presence of chilling stress

Abstract

The ameliorative role of 28-homobrassinolide under chilling stress in various growth, photosynthesis, enzymes and biochemical parameters of cucumber (Cucumis sativus L.) were investigated. Cucumber seedlings were sprayed with 0 (control), 10 -8 , or 10 -6 M of 28-homobrassinolide at the 30-day stage. 48 h after treatment plants were exposed for 18 h to chilling temperature (10/8 o C, 5/3 o C). The most evident effect of chilling stress was the marked reduction in plant growth, chlorophyll (Chl) content, and net photosynthetic rate, efficiency of photosystem II and activities of nitrate reductase and carbonic anhydrase. Moreover, the activities of antioxidant enzymes; catalase (E.C. 1.11.1.6), peroxidase (E.C.1.11.1.7), superoxide dismutase (E.C. 1.15.1.1) along with the proline content in leaves of the cucumber seedlings increased in proportion to chilling temperature. The stressed seedlings of cucumber pretreated with 28-homobrassinolide maintained a higher value of antioxidant enzymes and proline content over the control suggesting the protective mechanism against the ill-effect caused by chilling stress might be operative through an improved antioxidant system. Furthermore, the protective role of 28-homobrassinolide was reflected in improved growth, water relations, photosynthesis and maximum quantum yield of photosystem II both in the presence and absence of chilling stress.

Exogenous Brassinolide Enhances the Growth and Cold Resistance of Maize (Zea mays L.) Seedlings under Chilling Stress

“…Xu [58] and others have shown that BL can effectively alleviate the decrease in cucumber biomass caused by low temperature and can enhance the ability to resist chilling stress, by regulating the physiological metabolism of cucumber, thereby promoting the accumulation of dry matter [59]. The same conclusions have been corroborated in crops such as maize, rice and wheat [11,[60][61][62].…”

“…Huang [69] showed that chilling stress caused a decrease in the chlorophyll content and Pn of the herbaceous plant Dendrobium officinale, resulting in a decrease in maximum photochemical efficiency, which was significantly reduced by exogenous salicylic acid (SA) treatment. Chilling stress can significantly reduce maize Pn, and BLs can increase Pn under stress conditions, by increasing the chlorophyll content [70]; Fariduddin [59] used 28-homobrassinolide (HBL) to treat cucumber seedlings and found that the Pn, gs and Tr were significantly increased under low temperature and normal temperature conditions. This study showed that the application of exogenous BL at different concentrations could significantly alleviate the inhibitory effect of chilling stress on the Pn of maize seedlings, increase the gs and Tr, and significantly reduce the Ci.…”

The ameliorative effects of exogenous melatonin on grape cuttings under water‐deficient stress: antioxidant metabolites, leaf anatomy, and chloroplast morphology

“…In addition to the above-mentioned antioxidant enzymes and nonenzymatic antioxidants, plants may also increase the synthesis and accumulation of some nontoxic solutes (osmoprotectants) (e.g., proline, glycine, betaine, mannitol, soluble protein, soluble sugar) that regulate osmosis during normal cellular metabolism [61]. The production and accumulation of osmoprotectants occur in a broad spectrum of plant species in response to the osmotic stress caused by drought, salt, and chilling stress [62,63]. In the present study, the amount of proline in the plants treated with melatonin was considerably higher than that in plants that were not treated with melatonin under drought conditions, suggesting that melatonin may lessen the adverse effect of water-deficient stress on grape cuttings.…”

Brassinosteroid alleviates chilling-induced oxidative stress in pepper by enhancing antioxidation systems and maintenance of photosystem II

“…The present experiment demonstrated that low temperature increased contents of proline, soluble sugar and protein, and EBR treatment promoted the accumulation of these three osmoprotectants to a higher level (Table 3), indicating that EBR may induce a burst of organic solutes which might be tightly related to the improved cold resistance in pepper. The accumulation of organic and/or inorganic solutes by EBR in stressed plants has been observed to play an important role for normal cellular metabolism (Fariduddin et al 2011;ElBassiony et al 2012). …”

“…In plant, there are many defense mechanisms against low temperature, such as xanthophyll cycle, it can dissipate excess energy as heat through antenna of photosystem II to reduce ROS accumulation (García-Plazaola et al 2003;Weng et al 2006;Hu et al 2008). To protect from ROS damage, plants have evolved and developed a specialized antioxidative enzymatic systems including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), and they also generate various non-enzymatic antioxidants such as carotenoids, a-tocopherol, ascorbate and glutathione (Li et al 1998;Almeselmani et al 2006;Andre et al 2010;Fariduddin et al 2011).…”