Chill-induced inhibition of photosynthesis was alleviated by 24-epibrassinolide pretreatment in cucumber during chilling and subsequent recovery

Abstract

To investigate whether brassinosteroids (BRs) could be used to alleviate chill-induced inhibition of photosynthesis in cucumber (Cucumis sativus L) during chilling and subsequent recovery, the effects of exogenously applied 24-epibrassinolide (EBR) on gas exchange, chlorophyll fluorescence parameters, and antioxidant enzyme activity were studied. Cucumber plants were exposed to chilling under low light (12/8 o C and 100 μmol m -2 s -1 PPFD) for 3 days and then recovered under normal temperature and high irradiance (28/18 o C and 600 μmol m -2 s -1 PPFD) for 6 days. Chilling significantly decreased the net photosynthetic rate (P N ) and stomatal conductance (g s ), and increased rate of O 2˙formation and H 2 O 2 and malondialdehyde (MDA) content in cucumber leaves, but did not influence the optimal quantum yield of PSII (F v /F m ). Chilling also decreased the effective quantum yield of PSII photochemistry (Φ PSII ) and photochemical quenching (q P ), but induced an increase in nonphotochemical quenching (NPQ), and the activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX). High irradiance (600 μmol m -2 s -1 ) further aggravated the decrease in P N , g s , Φ PSII and q P , and enhanced the increase in reactive oxygen species (ROS) generation and accumulation in the first day of recovery after chilling. However, high irradiance induced a sharp decrease in F v /F m and NPQ, as well as the activities of SOD and APX on the first day of recovery. EBR pretreatment significantly alleviated chill-induced inhibition of photosynthesis during chilling stress and subsequent recovery period, which was mainly due to significant increases in g s , Φ PSII , q P and NPQ. EBR pretreatment also reduced ROS generation and accumulation, and increased the activities of SOD and APX during chilling and subsequent recovery. Those results suggest that EBR pretreatment alleviates the chill reduction in photosynthesis and accelerated the recovery rate mainly by increasing of the stomatal conductance, the efficiency of utilization and dissipation of leaf absorbed light, and the activity of the ROS scavenging system during chilling and subsequent recovery period. -light-adapted maximum fluorescence; F o -minimal fluorescence of dark-adapted state; F m -maximal fluorescence of dark-adapted state; F v /F m -optimal quantum yield of PSII; FM -fresh mass; g s -stomatal conductance; LT -low temperature; LTBR -low temperature; EBR-pretreatment; MDA -malondialdehyde; NT -normal temperature; NTBR -normal temperature/EBR-pretreatment; NPQ -nonphotochemical quenching; Φ PSII , -effective quantum yield of PSII photochemistry; P N -net photosynthetic rate; PPFD -photosynthetic photon flux density; q P -photochemical quenching coefficient; Rubisco -ribulose-1,5-bisphosphate carboxylase/oxygenase; ROS -reactive oxygen species; SOD -superoxide dismutase.

Effect of 24-epibrassinolide treatment on the metabolism of eggplant fruits in relation to development of pulp browning under chilling stress

“…Cold exposure can destroy the membrane structure because of lipid peroxidation, so an increase of MDA has been considered a marker for chilling injury. It has been demonstrated that lipid peroxidation and MDA content induced by cold stress can be suppressed by EBR treatment in cucumber and eggplant plants (Hu et al 2010;Wu et al 2014). In this study, the increase of MDA content in the controls progressed rapidly within the first 5 d of storage and then maintained constant.…”

“…In addition, treatment with exogenous brassinolide increased resistance of green bell pepper fruit to low temperature stress through a mechanism that improves the activity of antioxidant enzymes . 24-Epibrassinolide (EBR) is one of the most active forms of BRs available commercially, and has a favorable safety profile (Kuzmitsky and Mizulo 1991;Malikova et al 2008;Hu et al 2010). The use of EBR to enhance tolerance of eggplant seedlings to salt and cold stresses has been demonstrated (Wu et al 2014;Ding et al 2012).…”

Exogenous salicylic acid alleviates cold damage by regulating antioxidative system in two barley (Hordeum vulgareL.) cultivars

“…Antioxidant enzymes including SOD, CAT and POX are the most efficient protective mechanisms against oxidative stress (Senaratna et al 2000;Kang et al 2003;Patykowski and Urbanek, 2003;Hu et al 2010). They control the level of ROS and eliminate their detrimental effects.…”

“…The defence mechanisms against cold stress are quite complicated as both biochemical and physiological; however, it is well known that one of the most important among them is the antioxidative system. Because, similar to other stresses, reactive oxygen species (ROS) such as superoxide anion (O − 2 ), CONTACT Salih Mutlu salihmutlu@yahoo.com H 2 O 2 and hydroxyl radicals ( · OH) are produced during response to cold stress (Mutlu et al 2009a(Mutlu et al , 2009bHu et al 2010). Toxic levels of ROS can impair membrane permeability (Dias et al 2011) by inducing lipid peroxidation (Mutlu et al 2011;Esim et al 2014), cause damage to DNA and proteins (Bertrand et al 2011;Kekec et al 2013) and ultimately lead to programmed cell death.…”

“…Recently, some researchers carried out on winter wheat (Tasgin et al 2006) and watermelon (Yang et al 2008) demonstrated that exogenous SA treatment could be involved in cold tolerance by regulating the activities of antioxidant enzymes. The action mode of exogenous SA on the antioxidative system during response to cold and the time-dependent effect of SA when it was applied to a plant before cold exposure are still unclear although recent studies provide intensive data about the role of exogenous SA in the regulation of environmental stress response, including cold stress (Korkmaz, 2005;Shi et al 2006;Guo et al 2009;Mutlu et al 2009a;Xia et al 2009;Hu et al 2010;Dias et al 2011;Zhang et al 2011b;Luo et al 2012). On the other hand, there are inadequate and conflicting results in the literature about the effects of exogenous SA applied to a plant before cold stress treatment on the enzymatic antioxidative system.…”