Irrigation of Solanum lycopersicum L. with magnetically treated water increases antioxidant properties of its tomato fruits

Antioxidant effects of tomatoes (Solanum lycopersicum L.) have been studied and an association between dietary intake of tomatoes and lowered risk of cancer, neurodegenerative, and cardiovascular diseases has been suggested. Here we used magnetically treated water (MTW; 0.03–0.15 T), which promotes better germination and productivity in tomatoes, and we investigated the effects of aqueous and ethanolic (10–400 μg/ml) extracts of S. lycopersicum as potential antioxidant against 10 μM Fe(II)-induced thiobarbituric acid reactive species (TBARS) in liver and brain homogenates from rats. The ethanolic extracts from magnetically treated plants were more effective than aqueous extracts in preventing TBARS formation in brain and liver. The protective effects of ethanolic extract can be associated with antioxidants (polyphenols and flavonoids), lycopene and other lipophilic components found in the extract. In effect, magnetically treated plants had higher content of polyphenolic and flavonoid compounds than nontreated plants and they can be a better source of antioxidants than nontreated plants. Consequently, MTW can be used to produce functional foods with high contents of antioxidant components and may have better beneficial health effects than traditionally produced foods.     

再生水灌溉对黄瓜和西红柿养分元素分布特征及果实品质的影响

通过田间试验,研究再生水不同灌溉处理对黄瓜、西红柿植株各部位养分元素的分布特征及果实品质的影响.结果表明:再生水灌溉对西红柿的生长发育有促进作用,对黄瓜的生长发育有一定的抑制作用.再生水灌溉后,氮具有向植株地上部分运输的特征;钾易于在黄瓜叶片中富集,不易于在西红柿根部富集;钠主要富集在根系中,叶片中的浓度较低,不会对作物造成伤害;对各部位Ca2+、Mg2+、Cl-的分配没有显著影响.再生水灌溉对黄瓜、西红柿品质无显著影响,果实中硝态氮浓度分别增加了5.3%和32.9%,但均低于国家标准限值.     

冬小麦生长季不同灌溉模式对冬小麦-夏玉米产量与水分利用的影响

在华北平原黑龙港流域对冬小麦实行3种灌溉模式,研究了不同灌溉模式对冬小麦-夏玉米产量、耗水特性和水分利用效率的影响.结果表明:浇底墒水+拔节水处理(W2,75 mm+90 mm)和浇底墒水+拔节水+灌浆水处理(W3,75 mm+90 mm+60 mm)周年总产量均显著高于只浇底墒水处理(W1,75 mm),增幅分别为8.7%和12.5%.冬小麦全生育期对土壤水的消耗随灌溉量的增加而减少,夏玉米季总耗水量随冬小麦季灌溉量的增加而增加.W2处理冬小麦水分利用效率(WUE)比W3处理高11.1%,而其夏玉米水分利用效率(WUE)与W3处理差异不显著.W2和W1处理的周年水分利用效率(WUET)分别为21.28和21.60 kg.mm-1.hm-2,比W3处理分别高7.8%和9.4%.综合周年产量、耗水量和水分利用效率,W2是较好的节水丰产灌溉模式.     

Physiological behaviour, oxidative damage and antioxidative protection of olive trees grown under different irrigation regimes

Irrigation effects were investigated on an 8-year-old olive (Olea europaea L., cv. Cobrançosa) commercial orchard located in northeast Portugal. Trees were subjected to a rainfed control (T0) and three treatments (T1, T2, T3) that received a seasonal water amount equivalent to 30%, 60% and 100% of the estimated local evaporative demand by a drip irrigation system. Irrigation increases the photosynthetic activity of olive trees, in association with increases in water status, and reduces the midday and afternoon depression in gas exchange. The closely association between photosynthetic rate (A) and stomatal conductance (g _s) revealed that the decline in net photosynthesis over the course of the day was largely a consequence of stomatal limitation. However, the ratio of intercellular to atmospheric CO₂ concentration increased markedly from morning to midday in non-irrigated plants, in spite of lower g _s, suggesting that non-stomatal limitations of photosynthesis also occur when environmental conditions become more stressful. The occurrence of perturbations at chloroplastic level in rainfed plants was demonstrated by a lower maximum photochemical efficiency of photosystem II during the afternoon. Chlorophyll fluorescence measurements also revealed the occurrence of a dynamic photoinhibition in irrigated trees, mainly in T2 and T3, which seemed to be effective in protecting the photosynthetic apparatus from photodamage. Irrigation enhances antioxidant protection and decreases the oxidative damage at leaf level. Leaves grown under rainfed conditions revealed symptoms of oxidative stress, like the reduction (14%) in chlorophyll concentration and the increased levels (57%) of lipid peroxidation. We also found that the scavenging function of superoxide dismutase was impaired in rainfed plants. In contrast, the low thiobarbituric acid reactive substances concentration in T3 indicates that irrigation enhances the repairing mechanisms and decreases the oxidative damage by lipid peroxidation. Accordingly, leaves in T3 treatment had high levels of –SH compounds and the highest antioxidant potential. Meanwhile, the finding that guaiacol peroxidase activity increased in rainfed plants, associated with the appearance of oxidative damage, suggests that this enzyme has no major antioxidative function in olive.     

Effects of water stress on growth, osmotic potential and abscisic acid content of maize roots

Under water stress conditions, induced by mannitol solutions (0 to 0.66 M ) applied to the apical 12 mm of intact roots of Zea mays L. (cv. LG 11), a growth inhibition, a decrease in the osmotic potential of the cell sap and a significant accumulation of abscisic acid (ABA) were observed. When the roots were placed in a humid atmosphere after the stress, the growth rate increased again, even if elongation had been totally inhibited. Under a stress corresponding to an osmotic potential of -1.09 MPa in the solution, growth was totally inhibited, which means that the root cell turgor pressure was reduced to the yield threshold. These conditions led to the largest accumulation of ABA. The effect of water stress on the level of ABA was studied for three parts of the root. The greatest increase in ABA (about 10 fold) was obtained in the growth zone and this increase was apparently independent of the hydrolysis of the conjugated form. With a mannitol treatment of 1 h equivalent to a stress level of -1.39 MPa, a 4-fold increase in ABA efflux into the medium was obtained. These results suggest that there are interactions between water stress, root growth, osmotic potential and the ABA level. The growth under conditions of stress and the role of endogenous ABA in the control of plant metabolism, specially in the growth zone, are discussed.     

Prevalence, quantification and typing of adenoviruses detected in river and treated drinking water in South Africa

AIMS: Human adenoviruses (HAds), of which there are 51 serotypes, are associated with gastrointestinal, respiratory, urinary tract and eye infections. The importance of water in the transmission of HAds and the potential health risks constituted by HAds in these environments are widely recognized. Adenoviruses have not previously been quantified in river and treated drinking water samples. In this study, HAds in river water and treated drinking water sources in South Africa were detected, quantified and typed. METHODS AND RESULTS: Adenoviruses were recovered from the water samples using a glass wool adsorption-elution method followed by polyethylene glycol/NaCl precipitation for secondary concentration. The sensitivity and specificity of two nested PCR methods were compared for detection of HAds in the water samples. Over a 1-year period (June 2002 to July 2003), HAds were detected in 5.32% (10/188) of the treated drinking water and 22.22% (10/45) of river water samples using the conventional nested PCR method. The HAds detected in the water samples were quantified using a real-time PCR method. The original treated drinking water and river water samples had an estimate of less than one copy per litre of HAd DNA present. The hexon-PCR products used for typing HAds were directly sequenced or cloned into plasmids before sequencing. In treated drinking water samples, species D HAds predominated. In addition, adenovirus serotypes 2, 40 and 41 were each detected in three different treated drinking water samples. Most (70%) of the HAds detected in river water samples analysed were enteric HAds (serotypes 40 and 41). One HAd serotype 2 and two species D HAds were detected in the river water. CONCLUSIONS: Adenoviruses detected in river and treated drinking water samples were successfully quantified and typed. The detection of HAds in drinking water supplies treated and disinfected by internationally recommended methods, and which conform to quality limits for indicator bacteria, warrants an investigation of the risk of infection constituted by these viruses. The risk of infection may have implications for the management of drinking water quality. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is unique as it is the first report on the quantification and typing of HAds in treated drinking water and river water. This baseline data is necessary for the meaningful assessment of the potential risk of infection constituted by these viruses.     

Uniconazole-induced tolerance of rape plants to heat stress in relation to changes in hormonal levels, enzyme activities and lipid peroxidation

Winter rape (Brassica napus L. cv. 601) seedlings were treated with 50 mg.l-1of foliar-applied uniconazole and then exposed to heat stress with a light/dark temperature regime of 43 °C/38 °C for 3 days at the stem elongation stage. Heat stressed plants contained lower endogenous GA3, IAA and zeatin contents than the controls, while ABA content and ethylene level were increased significantly. Uniconazole-treated plants had lower endogenous GA3 and IAA contents, and higher zeatin and ABA contents and ethylene levels. Leaf chlorophyll content and respiratory capacity of roots were reduced markedly after plants were subjected to heat stress, and foliar sprays of uniconazole retarded the degradation of chlorophyll and increased respiratory capacity of roots. Following exposure to heat, the activities of superoxide dismutase and peroxidase were significantly reduced. Uniconazole-induced heat tolerance was accompanied by increased activities of various antioxidant enzymes. Foliar applications of uniconazole reduced electrolyte leakage and malondialdehyde accumulation caused by heat stress, suggesting that uniconazole may have decreased heat-induced lipid peroxidation and membrane damage. Foliar sprays of uniconazole increased the tolerance of rape plants to heat stress.     

Use of repetitive DNA sequences to determine the persistence of enteropathogenic Escherichia coli in vegetables and in soil grown in fields treated with contaminated irrigation water

AIMS: Fresh fruits and vegetables are increasingly recognized as vectors for food-borne illness. On farm contamination through contaminated irrigation water is considered likely source of the pathogen for several outbreaks. The purpose of this study is to investigate the possible similarity of strains of Escherichia coli isolated from the soil and vegetables irrigated by treated wastewater. METHODS AND RESULTS: Seventy-five strains of enteropathogenic Escherichia coli isolated from vegetables, soil and irrigation water were tested for sensitivity to antibiotics and shown to be sensitive. The result of enterobacterial repetitive intergenic consensus (ERIC)-PCR shows similarities between analysed strains isolated from the three different samples. Moreover strains of E. coli isolated from vegetables over different periods of time have the same ERIC-PCR profile. CONCLUSIONS: The isolated strains of enteropathogenic E. coli can persist in soil and in vegetables growing in fields treated with contaminated irrigation water for an extended period of time. SIGNIFICANCE AND IMPACT OF THE STUDY: Contaminated irrigation water can transport pathogenic bacteria, which persists in the soil for a long period of time and contaminates the vegetables growing in the field irrigated by this contaminated water.     

Impact of essential oils on growth rate, zearalenone and deoxynivalenol production by Fusarium graminearum under different temperature and water activity conditions in maize grain

AIMS: The effect of five essential oils (oregano, cinnamon, lemongrass, clove and palmarose) on growth rate, zearalenone (ZEA) and deoxynivalenol (DON) production by Fusarium graminearum strains was assessed. METHODS AND RESULTS: The influence of the essential oils was tested on irradiated maize at two concentrations (500 and 1000 mg kg-1), at different water activity (aw) (0.95 and 0.995) and temperature (20 and 30 degrees C) levels. At 0.995 aw all essential oils tested had an inhibitory effect on growth rate of F. graminearum at both temperatures studied. At this aw level, DON production in general was inhibited by all essential oils at 30 degrees C and, although palmarose and clove were the only essential oils with statistically significant inhibitory effect on ZEA production, an inhibitory trend was observed when cinnamon and oregano oils were added to maize grain. CONCLUSIONS: Antifungal and antimycotoxigenic activity of the essential oils assayed was shown to depend on environmental conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: It is apparent that essential oils should be considered as alternative preharvest natural fungicides. Further investigation on natural maize grain might be useful to study the effectiveness of these essential oils in the presence of natural mycoflora of maize grain.     

Effects of irrigation and air humidity preconditioning on water relations, growth and survival of Rosmarinus officinalis plants during and after transplanting

The effect of different irrigation and air humidity conditioning treatments on the morphological and physiological responses of Rosmarinus officinalis in nursery conditions was investigated in order to evaluate the degree of hardening resulting from these conditions. Rosmarinus officinalis seedlings were pot-grown during 4 months in two greenhouses (nursery period), in which two irrigation treatments were used (control and deficit). In one of these greenhouses, air humidity was controlled using a dehumidifying system (low humidity), in the other greenhouse the air conditions were not artificially modified (control humidity). After the nursery period, the plants of all treatments were transplanted and well watered (100% water holding capacity for 1 month, transplanting period). After this period, they received no water (establishment period). At the end of the nursery period it was seen that deficit irrigation had altered the morphology of the R. officinalis plants by reducing plant height, stem diameter, leaf area, total dry weight, and root length, while humidity influenced the parameters related with plant water relations. Low air humidity and deficit irrigation-induced tissue dehydration and lower stomatal conductance values (gs). The plants subjected to deficit irrigation developed leaf osmotic adjustment, which was maintained during the transplanting period. At that time, the plants that had been exposed to deficit irrigation and low humidity showed efficient stomatal regulation (lower gs values). After transplanting and during the establishment period, these plants showed a better water status (higher psil and gs values). Their post-planting survival rate improved as a result of acclimation processes.     

Comparison of exportation and metabolism of xylem-delivered ABA in maize leaves at different water status and xylem sap pH

³H-ABA was introduced into the xylem stream of maize ( Zea mays}) leaves on intact plants by incubation of a semi-attached flap of the sheath in solutions. The relative contribution of exportation and metabolism to the fate of xylem-delivered ABA was assessed in leaves which were either kept at different water potentials through soil drying treatments or subjected to different xylem pHs (pH 7.4 vs. pH 5.5) through a phosphate buffer in the feeding solutions. Xylem-delivered ABA was rapidly metabolised in well-watered leaves with a half-life of 2.19 h in the relatively mature leaves used in this study. Re-exportation of xylem-delivered ABA from leaves was much slower than metabolism. It took 24 h for half of the fed radioactivity to disappear from the well-watered leaves, and very possibly this radioactivity was in the form of metabolites of fed ³H-ABA. Although soil drying usually increases the output of ABA through phloem as reported in previous studies, it greatly reduced the re-exportation of xylem-fed ABA and/or its metabolites. Metabolism was also significantly reduced by the treatment of soil drying (half-life extended from 2.19 to 3.63 h), although the magnitude of change was much less than that of exportation. Manipulation of the pH in the feeding solution also had its effect on the re-exportation. A shift of pH from 5.5 to 7.4 reduced the rate of disappearance of the total radioactivity fed into the attached leaves, but showed no significant effect on the rate of ABA metabolism. It was concluded that it was the ABA metabolism, rather than a re-exportation from leaves, which was mainly responsible for the disposal of the ABA signal from the xylem and therefore preventing an accumulation in leaves. Water stress and pH increase of xylem sap would increase the time of such ABA's presence in the leaves. Since xylem-imported ABA is unlikely to be re-exported from leaves in its intact form, we believe a recycling of ABA from xylem to phloem through leaves plays only a minor role.     

Varietal influence of intercropped cowpea on the growth,yield and water relations of maize

The effects of three cowpea varieties namely, NewEra (a spreading type), Adzuki (an erect type) and Ife Brown (semi-erect) intercropped with maize on growth, yield and water relations of maize were investigated in the greenhouse and in the field. Cowpea varietal effects were significant on soil water extraction but insignificant on the performance of maize.     

Assessment of spring water quality and quantity, and health implications in Tongaren division, Nzoia River catchment, Kenya

Spring water is the common source of public water supply in most rural communities of developing countries such as Kenya. The water quality and quantity may be altered due to catchments degradation. This study was carried out in Tongaren division, Nzoia River catchment. The aim of this study was to investigate and map the occurrence and distribution of springs and to determine their water quality and quantity. This study determined the spring water discharge, conductivity, turbidity, total and thermotolerant (faecal) coliforms to assess suitability and sustainability of spring water for safe drinking. Twenty-eight springs were identified and their locations mapped using Global Positioning System (GPS) geo-reference data. Discharge ranged from 0.1 to 3 l s⁻¹, with some drying up during dry season. Total coliform was innumerable in most of the studied springs while thermotolerant (faecal) coliform counts occurred in eight springs, including four protected springs. This poses high risks of water-borne diseases. The water should be filtered and boiled prior to use for drinking. Facilitation of communities enabled development of seven springs to enhance water yield and quality. This study established high potential in the communities to develop springs and utilize the spring water as alternative source of livelihoods.     

Comparison of maize,permanent cup plant and a perennial grass mixture with regard to soil and water protection

Agricultural production of biogas maize (Zea mays L.) causes hazards to aquatic ecosystems through high levels of nitrogen (N) inputs. Newly introduced and already established perennial crops such as the cup plant (Silphium perfoliatum L.) and perennial grass mixtures offer the possibility of more environmentally friendly agricultural bioenergy production. The objectives of this field study were to quantify and compare soil mineral N, water infiltration, water runoff, soil erosion and N leaching under maize, permanent cup plant, and a perennial grass mixture. The study was conducted from October 2016 to March 2019 in Braunschweig, Germany. Plots with cup plant and grass mixture exhibited lower mineral N contents than maize, especially between 30 and 90 cm soil depth. Soil water infiltration was significantly different between the three crops. The grass mixture had the highest infiltration rates (6.2 mm/min averaged across 3 years), followed by cup plant (3.6 mm/min) and maize (0.9 mm/min). During wet periods, higher N leaching was found for maize (up to 42 kg N ha^?1 year^?1) than for cup plant (up to 5 kg N ha^?1 year^?1) or the grass mixture (up to 11 kg N ha^?1 year^?1). While runoff and erosion for cup plant and the grass mixture were negligible during the study period, considerable amounts of runoff water and eroded sediment of up to 1.5 Mg ha^?1 year^?1 were collected from the maize plots despite the near flat terrain of the experimental field. Overall, permanent cup plant proved suitable as a component for energy cropping systems to reduce the risk of N leaching and soil erosion, which is particularly important for the preventive flood protection in view of the more frequent occurrence of high intensity rainfall under climate change conditions.     

Benefits of alternate partial root-zone irrigation on growth, water and nitrogen use efficiencies modified by fertilization and soil water status in maize

Alternate partial root-zone irrigation (APRI) is a new water-saving technique and may improve crop water use efficiency without much yield reduction. We investigated if the benefits of APRI on biomass accumulation, water and nitrogen use efficiencies could be modified by different soil fertilization and watering levels in pot-grown maize (Zea mays L. cv. super-sweet No 28, a local variety). Three irrigation methods, i.e. conventional irrigation (CI), alternate partial root-zone irrigation (APRI, alternate watering on both sides of the pot) and fixed partial root-zone irrigation (FPRI, fixed watering on one side of the pot), two watering levels, i.e. water deficit (W₁, 45–55% of field capacity) and well-watered (W₂, 70–80% of field capacity), and two N fertilization levels, i.e. no fertilization and fertilization, were designed. Results showed that APRI and FPRI methods led to more reduction in transpiration than in photosynthesis, and thus increased leaf water use efficiency (leaf WUE, i.e. the ratio of leaf net photosynthetic rate to transpiration rate). Compared to the CI treatment, APRI and FPRI increased leaf WUE by 7.7% and 8.1% before the jointing stage and 3.6% and 4.2% during the jointing stage, respectively. Under the fertilization and well-watered conditions, APRI treatment saved irrigation water by 38.4% and reduced shoot and total dry masses by 5.9% and 6.7%, respectively if compared to the CI treatment. APRI also enhanced canopy WUE (defined as the amount of total biomass per unit water used) and nitrogen (N) apparent recovery fraction (Nr, defined as the ratio of the increased N uptake to N applied) by 24.3% and 16.4%, respectively, indicating that effect of APRI can be better materialized under appropriate fertilization and water supply. Responsible Editor: Rana E. Munns     

Antioxidative defenses and water deficit-induced oxidative damage in rice (Oryza sativa L.) growing on non-flooded paddy soils with ground mulching

Rice (Oryza sativa L.) cultivation under non-flooded conditions using polyethylene film as ground mulching materials, namely plastic film-mulching cultivation system (PFMCS), is an alternative to the conventional rice cultivation system in regions where rainfall and fresh water resources are limited. Two-year field trials (1998–1999) were performed in this study to investigate the growth-stage-dependent changes in activities of antioxidative enzymes and lipid peroxidation in leaves of rice subjected to mulching with plastic film or kraft paper and zero mulching under non-flooded conditions compared with continuously flooded treatment. Significantly higher activities of peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) but lower concentration of malondialdehyde (MDA) were observed in mulching treatments than in zero mulching treatment at all growth stages in the drier growing season (1999). The concentration of MDA was significantly higher especially at late growth stages in zero mulching treatment than in the other treatments. In contrast, essentially no significant difference existed in the activities of the major antioxidant enzymes (except POD) or in the concentration of MDA between any two treatments in the wetter growing season (1998). This change tendency of antioxidant enzyme activity and MDA level over two contrasting growing seasons was in line with both soil and leaf moisture status, and rice yields of different treatments. These results strongly suggest that plastic film-mulching treatment or paper mulching treatment significantly alleviated oxidative damages induced by water-deficit stress in rice. The efficacy of ground-mulching-induced enhancement of antioxidative defense to drought stress is discussed with respect to water deficit status in both soils and rice plants.     

Water stress effects on leaf elongation,leaf water potential,transpiration, and nutrient uptake of rice,maize, and soybean

A pot experiment was conducted in the greenhouse to determine and compare the responses of rice (Oryza sativa L. var, IR 36), maize (Zea mays L. var. DMR-2), and soybean (Glycine max [L.] Merr. var. Clark 63) to soil water stress. Leaf elongation, dawn leaf water potential, transpiration rate, and nutrient uptake in stressed rice declined earlier than in maize and soybean. Maize and soybean, compared with rice, maintained high dawn leaf water potential for a longer period of water stress before leaf water potential. Nutrient uptake under water stress conditions was influenced more by the capacity of the roots to absorb nutrients than by transpiration. Transport of nutrients to the shoots may occur even at reduced transpiration rate It is concluded that the ability of maize and soybean to grow better than rice under water stress conditions may be due to their ability to maintain turgor as a result of the slow decline in leaf water potential brought about by low, transpiration rate and continued uptake of nutrient, especially K, which must have allowed osmotic adjustment to occur.     

Influence of irrigation rhythm and water supply on growth,water status and yield of egg-plant (Solanum melongena L.)

Summary The responses of two egg-plant varieties to irrigation rhythm and water supply based on daily potential evapotranspiration were performed on St-Paul silt loam.Results showed that a shorter irrigation rhythm gives the best production in terms of fruit yield (Table 1). Daily irrigation gives a leaf blade with a lower specific weight than the bi-weekly irrigation rhythm during the whole sampling period (Fig. 1).When we compared 4 quantities of water representing 40 to 100% of the potential evapotranspiration, the best results in terms of fruit yield were obtained with the irrigation giving 80% of the potential evapotranspiration (Table 2). But there is no significant difference between the specific leaf weights (Fig. 2).When we observed the varietal behaviour we found that the cultivar Violette de Barbentane gives a production 20% higher than that of Ronde de Valence. But the water potential and transpiration resistance of leaves are not very different for the two varieties (Figs. 5 and 6).The results about the influence of varieties come from one part of the study by M. Pochard and Serieys of the Station of Genetics.     

调亏灌溉和生物炭对大豆生长、产量及水分利用效率的影响

为了解生物炭及调亏灌溉对大豆的影响,以大豆"开育12号"为试验材料,采用随机区组试验设计,利用盆栽栽培条件,研究不同生物炭添加量B₀(0 t·hm^-2)、B₁(6t·hm^-2)、B₂(12 t·hm^-2)和不同程度调亏灌溉W₁(充分灌溉,70%田间持水量)、W₂(轻度调亏,55%～60%田间持水量)、W₃(重度调亏,45%～50%田间持水量)对大豆生长、产量及水分利用的影响。结果表明:轻度调亏灌溉不会影响大豆叶面积指数及地下部分干物质累积量,而大豆叶面积指数和地下部分干物质累积量随着生物炭使用量的增加而增加;地上部分干物质累积量随着调亏程度的加重而降低,而生物炭施用量为12 t·hm-2时,才会提高地上部分干物质累积量。调亏灌溉和生物炭均能影响大豆的耗水量,其中耗水量随着调亏程度的加剧而减少,而添加6 t·hm^-2生物炭耗水量最高,但有利于产量的形成。与充分灌溉不施用生...     

Effects of 24-epibrassinolide on seed germination, seedling growth, lipid peroxidation, proline content and antioxidative system of rice (Oryza sativa L.) under salinity stress

The effects of 24-epibrassinolide (24-epiBL) on seedling growth, antioxidative system, lipid peroxidation, proline and soluble protein content were investigated in seedlings of the salt-sensitive rice cultivar IR-28. Seedling growth of rice plants was improved by 24-epiBL treatment under salt stress conditions. When seedlings treated with 24-epiBL were subjected to 120 mM NaCl stress, the activities of superoxide dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6) and glutathione reductase (EC 1.6.4.2) did not show significant difference, whereas the activity of ascorbate peroxidase (EC 1.11.1.11) significantly increased. Increased activity of peroxidase (EC 1.11.1.7) under NaCl stress showed remarkable decrease in the 24-epiBL+NaCl-applied group. Lipid peroxidation level significantly increased under salt stress but decreased with 24-epiBL application revealing that less oxidative damage occurred in this group (24-epiBL+NaCl). In addition, increased proline content in the NaCl-applied group was decreased by 24-epiBL application in the 24-epiBL+NaCl-applied group. Soluble protein content was increased by 24-epiBL application even under NaCl stress, being also higher than control conditions (no 24-epiBL or NaCl treatment). 24-epiBL treatment considerably alleviated oxidative damage that occurred under NaCl-stressed conditions and improved seedling growth in part under salt stress in sensitive IR-28 seedlings.