Heat stress
Sabrieh Seimrizade; Ali Moshatati; Abd-AlMahdi Bakhshandeh; Aydin Khodaei Joghan; Ahmad Koochekzadeh
Abstract
IntroductionTerminal heat stress in Khuzestan province, decrease growth, yield and yield components of wheat. The vermicompost fertilizer improve water reserve and physical and chemical properties of soil. One of the important ways to reduce the negative effect of terminal heat stress on plant is using ...
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IntroductionTerminal heat stress in Khuzestan province, decrease growth, yield and yield components of wheat. The vermicompost fertilizer improve water reserve and physical and chemical properties of soil. One of the important ways to reduce the negative effect of terminal heat stress on plant is using vermicompost fertilizer in the soil. Using vermicompost fertilizer in agricultural soils lead to increase nutrient elements and conserving the soil water and decrease the negative impacts of drought stress on plant. Generally, vermicompost fertilizer contribute to preserving the moisture storage of the soil and to supply the nutrients required by the plant. In this study, the most important aim is to study the effect of vermicompost fertilizer on bread wheat yield and yield components under terminal heat stress in Ahwaz climatic condition. Materials and methodsIn order to evaluate the effect of vermicompost fertilizer on growth and yield of wheat in terminal heat stress of Ahwaz, a field experiment using split-plot design based on randomized complete block design with four replicates was conducted in research farm of Agricultural Sciences and Natural Resources University of Khuzestan during (in 31º N, 48º E, 35 Km north-east of Ahwaz, and 20 m above the sea level) 2017-2018 growing season. Experimental factors were three sowing dates (22 Nov., 11 Dec. and 31 Dec.) in main plots and five vermicompost rates (0 (control), 5, 10, 15 and 20 t.ha-1) in sub plots. Results and discussionAnalysis of variance showed that the effect of sowing date and vermicompost were significant on measured traits. Mean comparison revealed that the highest grain yield (2356 kg.h-1) was at the first sowing date and the lowest grain yield (1732 kg.h-1) was at the last sowing date. Also, in vermicompost levels, the maximum grain yield (2593 kg.ha-1) was in 20 t.ha-1 of vermicompost application and the minimum grain yield (1566 kg.ha-1) was in control of vermicompost. ConclusionsGenerally, the results showed that with delay in sowing date and occurrence of terminal heat stress, decreased growth and grain yield of wheat. But, using vermicompost fertilizer decreased the negative impact of drought stress. So that, with increase vermicompost application, increased measured traits. Also, in areas with terminal heat stress after flowering stage, using 20 tons per hectare of vermicompost fertilizer is recommended for maintaining grain yield.
Hadis Hasanvand; seyedata siadat; AbdolMehdi Bakhshandeh; Mohammad Reza Moradi Telavat; Adel Poshtdar
Abstract
Introduction Borage (Borago officinalis L.) is an annual plant and belongs to the Boraginasea family, that afford curative properties. This plant has deep roots and can absorb soil, water and nutrients from the depths of the soil, and is therefore somewhat resistant to drought. Increasing people's tendency ...
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Introduction Borage (Borago officinalis L.) is an annual plant and belongs to the Boraginasea family, that afford curative properties. This plant has deep roots and can absorb soil, water and nutrients from the depths of the soil, and is therefore somewhat resistant to drought. Increasing people's tendency toward medicinal plants to treat diseases has conduct to and essential the cultivation of medicinal plants globally and in Iran. Water deficit stress is one of the most important non- biological stresses that reduces water absorption by root system. Water deficit is considered as the most important limiting factor for non-living plant growth and yield that, in addition to a negative effect on yield, causes exacerbates other stresses, in particular the stress of the deficiency of nutrients in the plant. Drought stress is one of the most important limiting factors yield in the world. Today, phenolic compounds and plant growth regulator has been proposed, to reduce the negative effects of stress. Thus, this experiment carried out in order to Effects of salicylic acid on yield and nutrient uptake borage (Borago officinalis L.) under interrupting irrigation conditions. Materials and methods A field study was conducted as a split plot arrengement based on randomized complete blocks design (RCB) with four replications at farm at experimental field of Khouzestan Agriculture Science and Natural Resources University, Iran during 2017-2018 cropping season. Three interrupting irrigation (stress at stemming stage, stress at flowering stage, stress at seed fill stage and control) as main plat and four application of salicylic acid including of 0, 69, 138 and 207 mg.L-1 as sub plots comprised experimental treatment. With reach each of these stages, from stem emergence to flowering initiation, from flowering initiation to seed fill interrupting irrigation and from seed fill initiation to beginning seed harvesting interrupting irrigation was carried out. This continued until the end of the physiological stages. Salicylic acid application was carried out during two stages during vegetative period (stem emergence and flowering initiation) simultaneously with applying moisture stress treatment. After applying the respective treatments, traits were measured at full flowering stage. Grain yield, oil percentages, ash contents of flower and leaf, nutrients of nitrogen, phosphorus, potassium, and sodium in two parts of the flower and leaf of Borage were measured. Analysis of variance and comparison of means was performed by SAS software and test LSD, 5% level probability .Respectively. Results and discussion The result of analysis of variance showed that interrupting irrigation and salicylic acid had significant effect on grain yield, oil percentages, ash contents of flower and leaf ash and nutrients of nitrogen, phosphorus, potassium, and sodium in two parts of the flower and leaf. Also interaction effect of interrupting irrigation and salicylic acid on flower ash, potassium flowers, and leaf, phosphorus and sodium flowers was significant. Mean comparison test showed that with interrupting irrigation in stemming and flowering stages, only the concentration of sodium and potassium elements and oil percentages increased significantly. Maximum grain yield in the control treatment was 633.43 kg. ha-1. Foliar application with 207 mg.L-1 salicylic acid increased 50% grain yield. Salicylic acid increased all the traits studied, other than sodium. Consumption of 138 mg.L-1 salicylic acid in interrupting irrigation condition increased 36% of flower ash and 38% of leaf phosphorus, due to non-consumption of salicylic acid and drought stress. The highest amount of potassium of flower and leaf were obtained by application 138 and 207 mg.L-1 salicylic acid in interrupting irrigation stress at flowering stage and maximum flowering sodium without application salicylic acid with interrupting irrigation in this stage. Conclusion The results suggested salicylic acid application in borage can increase uptake of macro nutrients required for plant growth and reduce the negative effects of drought stress damage.
Alireza Borjian Boroujeni; Seyed Ataollah Siadat; Abdolmahdi Bakhshandeh; Khalil Alami-Saeid; Mohamadreza Jalal-Kamali
Abstract
IntroductionHeat stress during reproductive development is the main limitation in the production of wheat in most of the wheat fields in the world. It is important to recognize the physiological and molecular mechanisms associated with heat tolerance and the detection of screening methods in improving ...
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IntroductionHeat stress during reproductive development is the main limitation in the production of wheat in most of the wheat fields in the world. It is important to recognize the physiological and molecular mechanisms associated with heat tolerance and the detection of screening methods in improving plants to tolerate heat. In Iran data from the effect of short-term heat wave on yield and physiological mechanisms do not exist under field conditions. The objective of this study was to determine the effects of short-term heat stress near flowering and early grain filling on grain yield and physiological parameters. Materials and methodsThis research was conducted at research farm of Khuzestan Agricultural Sciences and Natural Resources University, located 35 km northeast of Ahwaz, in 2014. Four wheat genotypes (Chamran. Maroon, Arvand and Atrak) were exposed to heat stress (maximum 35 °C) for a three-day in the field with a portable heat chamber at two different stages, near flowering (H1) and early grain set (H2). Chlorophyll content was measured using manual chlorophyll. Stomatal conductance was performed from the top three leaves of selected plants. Chlorophyll concentration was calculated using the Arnon method (1949). Cell membrane thermostability (CMTS) were calculated using the following equation: CMTS (%) = [1- (EC1 / EC2)] × 100where EC1 and EC2 are the primary electrical conductivity (before the autoclave) and the secondary (after the autoclave), respectively. Proline was maesured using Bates method (1973). Ascorbate peroxidase (APX) activity was measured using Nakano and Asada method (1987). Catalase (CAT) activity was measured using Aebi method (1983), peroxidase activity (POX) was measured using Chance and Maehly method (1955), Superoxide dismutase was measured using Biochamp and Fridovich method (1971). Malon de aldehyde (MDA) was measured using Hess and Packer (1969). All calculations were performed using the SAS-9.4 statistical software. Factor analysis was done by using principal component analysis and Varimax rotation on the temporary factor. Results and discussionThe results of analysis of variance showed that there were significant differences between heat stress levels and the traits of genotypes. Short-term heat stress (H1 or H2) decreased the average grain yield of Chamran, Maroon, Arvand and Atrak genotypes by 19.6, 18.6, 17.8 and 11.2 percent. Heat stress significantly caused to reduce water potential, chlorophyll fluorescence, leaf relative water content and cell membrane thermostability whereas stomatal conductance, chlorophyll destruction rate and proline content increased. Although there was no significant effect of short term heat stress on total chlorophyll concentration in this experiment, there was a negative correlation between grain yield and total chlorophyll concentration (r = -0.67 in H1 and r = -0.77 in H2). The activity of catalase, peroxidase and superoxide dismutase increased significantly in response to H1 or H2. The results of the factor analysis showed that four factors explained 86.7% and three factors explained 86.4% the variance among varieties in H1 and H2, respectively. Atrek, Chamran and Arvand varieties tolerated heat stress than Maroon variety by more photosynthesis persistency, higher metabolite content and more enzyme defense mechanism. It could be argued that cultivars with slower rate of leaf senescence after heat exposure and more enzymatic protection could be more tolerant to heat stress.
Alireza Borjian Boroujeni; Abdolmahdi Bakhshandeh; Seyed Ataollah Siadat; Khalil Alami-Saeid; Mohamadreza Jalal-Kamali
Abstract
IntroductionShort periods of heat stress in spring under Mediterranean climate (e.g. southern vast areas of Iran) are common and cereal crops often exposed to short periods of elevated temperatures which can have large effects on crop yields. Stem water-soluble carbohydrate (WSC) could be an important ...
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IntroductionShort periods of heat stress in spring under Mediterranean climate (e.g. southern vast areas of Iran) are common and cereal crops often exposed to short periods of elevated temperatures which can have large effects on crop yields. Stem water-soluble carbohydrate (WSC) could be an important carbon bank for supporting grain filling in wheat especially when carbon assimilation is hampered by heat stress. In Iran, a large number of studies have been done on the effects of heat stress on grain yield of wheat and its components, based mainly on the change in planting date, and data from the effect of short-term heat wave on yield and grain growth and the role of WSC in developing grains do not exist under field conditions. The aim of this study was to determine the effects of short-term heat stress before flowering and the beginning of grain filling on peduncle WSC and grain filling pattern as well as determination of the contribution of peduncle WSC in genotypes with different amounts of carbohydrates in grain growth under short-term stress conditions. Materials and methodsThis research was carried out at Research Farm of Khuzestan Agricultural Sciences and Natural Resources University, located 35 km northeast of Ahwaz, in 2014. Four wheat genotypes (Chamran. Maroon, Arvand and Atrak) were exposed to heat stress (maximum 35 °C) for a three-day in the field with a portable heat chamber at two different stages, near flowering (H1) and early grain set (H2). to investigate the changes in individual grain weight (IGW) during grain development, the total WSC changes in the peduncle of the main stem after exposure to short-term heat stress during the development of grain, three plants marked from day zero after flowering. The grains were harvested at intervals of seven days until the time of maturity. The total WSC were measured by anthrone method. When the dry weight of peduncles was maximized in each genotype, the concentration of peduncle carbohydrates (WSC-C) was considered as the maximum WSC-C. To calculate the maximum peduncle WSC content, the maximum WSC-C was multiplied by the maximum peduncle weight. The difference between peduncle WSC-C at maximum time and at maturity time was considered as the mobilized WSC from peduncle to grain. The ratio (%) of peduncle mobilized WSC to maximum peduncle WSC-C was calculated as the efficiency of peduncle in mobilized WSC. The analysis of variance of the measured traits in this study was performed using SAS 9.4 software. Duncan's test was done for means comparison. Results and discussionThe results of analysis of variance showed that there were significant differences between heat stress levels and the traits of genotypes. Short term heat stress (H1 or H2) caused a significant reduction in individual grain weight (IGW) and grain number of main spike. There was no detectable change in IGW until 14 days post-anthesis, after which time grain growth in the heat-stressed plants was reduced from 4.5% to 17%. Based on number of grain per spike and IGW, Atrak, Chamran and Arvand genotypes were recognized as tolerant gynotypes. Heat stress (average of H1 and H2) reduced maximum peduncle water soluble carbohydrate (WSC) content by 26% and mobilized WSC by 15%. The reduction of peduncle WSC content by the heat stress treatments appeared to start at 21 days post-anthesis Reductions in IGW and among genotypes were negatively correlated to the maximum peduncle WSC content (P
Omran Parsapour; Abdolmahdi Bakhshandeh; Mohammad Hossein Gharineh; Hasan Feisi; Mohammad Reza Moradi Telavat
Abstract
Introduction Under water shortage, applying and adjusting of some elements concentration such assilicon (Si) can be used as a strategy to reducethe negative effects of stress on wheat(Triticum aestivum L.) growth and enhanced plant compatibility.Some of the studies showed that exogenousSi application ...
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Introduction Under water shortage, applying and adjusting of some elements concentration such assilicon (Si) can be used as a strategy to reducethe negative effects of stress on wheat(Triticum aestivum L.) growth and enhanced plant compatibility.Some of the studies showed that exogenousSi application increased crop resistance to environmental stresses such as drought (Ahmed et al., 2011; Maghsoudi and Emam, 2016). Likewise, macro and micro nano fertilizers application caused an increase in crop yield. Therefore, this study aimed to investigate the effect of foliar application of nano and bulk Si dioxide particles on yield and yield components of wheat and also to determine the contribution of different sources in grain yield formation. Materials and methods In order to investigate the effect of foliar application of silicon on yield and redistribution of wheat dry matter under drought stress conditions, a field experiment was conducted as split plots based on a randomized complete block design with four replications at Ramin Agriculture and Natural Resources University of Khuzestan. Drought stress periods included three levels of normal irrigation (full irrigation throughout growing season or control), drought stress from stem elongation to flowering and drought stress from flowering to maturity were considered as main plot and foliar application of silicon dioxide levels in seven levels including non-foliar application (control), application of nano and bulk particles of silicon dioxide in concentrations of 50, 100 and 150 mg L-1 were considered as subplots. Data analysis was performed using SAS software and GLM procedure, and means comparison was carried out using a protected LSD method at a 5% probability level. Results and discussion Drought stress from stem elongation to flowering reduced the number of fertile tillers, number of spikelets per spike and number of seeds per spike, thereby reducing seed yield by about 35% compared to full irrigation conditions. Drought stress in the grain filling period resulted in a 10% reduction in wheat 1000-grains weight. Silica foliar application slightly reduced the effect of drought stress on grain yield.Wheat grain yield was significantly higher than other spraying treatments with the application of concentration of 100 mg L-1 of nano silicon particles (61.71 g m-2) and 150 mg L-1 of bulk silicon particles (572.73 g m-2). The efficiency of redistribution of dry matter in drought stress conditions from stem elongation to flowering (18.46%) was significantly higher than non stress conditions (14.07%) or stress induced from flowering stage to end of growth period (13.75%) Regardless of Silica foliar application treatments, redistribution of dry matter under full irrigation conditions was about 11% less than that of drought stress. The highest percentage of redistribution of dry matter from wheat grain yield was related to foliar application with concentration of 100 mg L-1 of bulk silicon particles under drought stress from flowering to the end of the growth period. The contribution of current photosynthesis in grain filling in non-stress conditions (458.68 g m-2) was significantly higher than drought stress conditions from flowering stage to end of growth period (399.68 g m-2) and for this was also significantly more than that of the stress conditions from the stem elongation to flowering (261.98 g m-2). The contribution of current photosynthesis in grain filling in spray treatment with a concentration of 100 mg L-1 of nano silicon dioxide was the maximum (451.25 g m-2) and in control treatment was at least (311.11 g m-2). It seems that nano silicon particles application caused an increase in plant tolerance to drought stress due toincreasing water balance, photosynthetic efficiency, and seedling growth (Hattori et al., 2005). Conclusion In general, the present study showed that the presence of silicon and especially nano particles in drought stress has a significant role in improving yield and grain yield components of wheat as well as redistribution of dry matter. It seems that in order to reduce the negative effect of moisture stress during wheat growth season and increase grain yield and dry matter redistribution, application of 100 mg L-1of nanosilica particles is recommended.
Abolfazl Derakhshan; Abdolmahdi Bakhshandeh; S. Ataollah Siadat; Mohammad Reza Moradi Telavat; Bahram Andarzian
Abstract
Introduction Some seeds will enter thermoinhibition when imbibed at warm temperature regimes. Seed thermoinhibition is the situation when germination of seeds that have been imbibed at warm temperature is prevented, but the seeds will subsequently germinate rapidly when the temperature is reduced. It ...
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Introduction Some seeds will enter thermoinhibition when imbibed at warm temperature regimes. Seed thermoinhibition is the situation when germination of seeds that have been imbibed at warm temperature is prevented, but the seeds will subsequently germinate rapidly when the temperature is reduced. It is therefore a temporary inhibition of germination that can be alleviated simply by lowering the temperature. This process generally occurs at temperatures considerably lower than ceiling temperature. It may also occur over a small range of temperatures, such that germination can go from 100 to 0 % when the upper temperature limit is exceeded by only a few degrees. This germination behavior is often associated with a winter annual life cycle common in Mediterranean-type climates with wet winters and dry summers, as seeds that are shed in early summer and have subsequently after-ripened nonetheless may not germinate when hydrated at warm temperatures, waiting instead until the fall for cooler temperatures and more certain rainfall before germinating. Patterns of seed germination behavior of different populations in response to warm temperatures can be described using the models based on thermal-time units. In this study, thermal-germination model was developed based on four different probability distribution functions of Normal, Lognormal, Gumbel and Weibull. Seed thermoinhibition in six cultivars of spring oilseed rape (Brassica napus L.) were then quantified using these models. Materials and methods Experiment was conducted at the Seed Technology Laboratory, Ramin Agriculture and Natural Resources University, Khuzestan. In this study, germination responses of six spring oilseed rape cultivars (Sarigol, RGS003, Dalgan, Hyola-401, Jerry and Julius) were investigated at constant temperatures. Germination test were conducted in the dark at eleven constant temperature regimes of 8, 12, 16, 20, 24, 28, 32, 33, 34, 35 and 36 ºC with a range of ±0.2 ºC. For each cultivar, germination test was carried out in a completely randomized design with four replications and the entire experiment was repeated three times. The germinated seeds (criterion, radicle protrusion of > 2 mm) were counted and removed at specified intervals. Seeds of all cultivars germinated more rapidly at 32 ºC than at higher or lower temperature regimes. Therefore, the optimum temperature for germination was assumed to be 32 ºC. Above this, oilseed rape seeds showed thermoinhibition of germination. So that, ungerminated seeds of each cultivar at these warm temperature regimes were germinated rapidly at low temperature of 20 ºC. Cumulative-germination curves of oilseed rape cultivars in temperatures beyond 32 ºC were used to perform non-linear regression procedures to assess the relative accuracy of different thermal-germination models in predicting germination response under constant temperatures. The thermal-germination models were fitted to the germination data of each cultivar using the PROC NLMIXED procedure of SAS. Assessment of goodness-of-fit was performed by the Akaike information criterion (AIC). Results and discussion Assess the goodness of fit indicated that precision of the thermal-germination models was different in describing the germination behavior of early- and mid-maturing cultivars of oilseed rape. Thermal-germination model based on Normal distribution provide the best fit to data of germination progress over time for early-maturing cvs. Dalgan (AIC=-237.5) and Hyola-401 (AIC=-168.8). For mid-maturing oilseed rape cultivars (Sarigol, RGS003, Jerry and Julius), the smallest AIC values were obtained for the Gumbel thermal-germination model, while the model based on Normal distribution gave the worst fit to germination data. The germination responses of early- and mid-maturing oilseed rape cultivars to supra-optimal temperature regimes were different. Early-maturing cultivars showed 5, 50 and 95% thermoinhibition of germination at averaged temperatures of 33.52, 33.99 and 34.37 ºC, respectively. While, seed thermoinhibition in mid-maturing cultivars reached to 5, 50 and 95 % of maximum at averaged temperatures of 33.63, 34.34 and 35.59 ºC, respectively. Based on the model prediction, the germination completely inhibited at an average temperature of 34.54 ºC in early-maturing cultivars and an average temperature of 36.64 ºC in mid-maturing cultivars. Abscisic Acid (ABA) has been reported as the major regulator of seed thermoinhibition. Conclusions Early-maturing oilseed rape cultivars have lower thermal-thresholds compared to mid-maturing cultivars. A different thermal-germination model was necessary for predicting the probability of seed germination in response to warm temperature regimes depending on the type of germination behavior of early- and mid-maturing cultivars. Thermal-germination models proposed here well described the observed thermoinhibition response of seed germination in oilseed rape cultivars.
Ali Moshatati; Seyed Ataollah Siadat; AbdolMahdi Bakhshandeh; Mohammad Reza Jalal-Kamali
Abstract
Introduction Temperature is the most important determining factor in growth and development duration length of crops. Temperature increase result in faster growth and development and shorter life duration of plant. This is one of the main factors of yield loses in hot environments (Aggravel, 1991). Studies ...
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Introduction Temperature is the most important determining factor in growth and development duration length of crops. Temperature increase result in faster growth and development and shorter life duration of plant. This is one of the main factors of yield loses in hot environments (Aggravel, 1991). Studies showed that one centigrade increase in mean temperature of growth duration causes eight days (6 percent) decrease in vegetative growth phase, two days (five percent) decrease in filling period duration and 21 days (eight percent) decrease in life cycle duration of wheat (Koocheki and Hosseini, 2006). Modhej et al. (2007), planted six wheat cultivars (three bread wheat cultivars and three durum wheat cultivars) in two sowing dates (November 21 as optimum sowing date and January 20 as late sowing date) and reported that grain filling period of late sowing date confronted to terminal heat stress and resulted in significantly decrease in grain weight and grain yield. In this study, the most important aim is to study the effect of terminal heat stress on growth periods length, grain yield and its components and grain yield formation rate and its components in 20 spring bread wheat cultivars in Ahwaz condition. Materials and methods In order to study the effect of terminal heat stress on growth periods length, grain yield and its components and grain yield formation rate and its components in 20 spring bread wheat cultivars, a field experiment was conducted in a stripe block arrangement using a complete randomized block design (CRBD) with three replications in research field of Ramin Agriculture and Natural Resources University of Khouzestan (in 31º N, 48º E, 35 Km north-east of Ahwaz, and 20 m above the sea level) during two cropping seasons (2007-2008 and 2008-2009). Experimental factors were four sowing dates (06 Nov. (early), 06 Dec. (timely), 05 Jan. (late) and 04 Feb. (very late)) in vertical plots and 20 spring bread wheat cultivars (Atrak, Arvand1, S-80-18, Star, Inia66, Bolani, Bayat, Pishtaz, Chamran, Chenab70, Darab, Dez, Roshan, Shoeleh, Kavir, Maroon, Hamoon, Hirman and Vee/Nac) in horizontal plots. Results and discussion Results showed that year, sowing date, genotypes and sowing date× genotype had significant effect on measured traits. Mean comparisons revealed that with delay in sowing date and increase in mean temperatures of growing season, decreased the day from sowing to anthesis, day from anthesis to maturity, day from sowing to maturity, grain number in m2, thousand grain weight and grain yield that resulted to decrease in grain formation rate, grain filling rate and grain yield formation rate. Generally, Maroon and Shoeleh cultivars (early- lately maturity cultivars) with short period of sowing to anthesis and with long period of anthesis to maturity, had longer grain filling period. Conclusions Generally and according to these results could say that delay in sowing and increase in temperature of growth cycle duration resulted in confrontation of terminal phases of growth and development to high temperatures and occurrence the terminal heat stress. These stress decreased the day from sowing to anthesis, day from anthesis to maturity and day from sowing to maturity. These effects resulted in lower grain number in m2, thousand grain weight and grain yield. Finally, above decreases lead to lower grain formation rate, grain filling rate and grain yield formation rate.
Zohreh Emami Bistgani; S.A. Siadat; A. Bakhshandeh; A. Ghasemi Pirbalouti
Abstract
Introduction Thymus daenensis as a medicinal plant dispersed in high altitudes in Zagros Mountains range, western and south western Iran and has an extensive diversity of chemical composition of essential oil (Ghasemi Pirbalouti et al., 2014). Water stress has been considered as one of the limit ...
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Introduction Thymus daenensis as a medicinal plant dispersed in high altitudes in Zagros Mountains range, western and south western Iran and has an extensive diversity of chemical composition of essential oil (Ghasemi Pirbalouti et al., 2014). Water stress has been considered as one of the limit factors for plant production (Passioura, 2007). Drought condition frequently leads to oxidative stress primarily due to chloroplast damaging and injury, leading to over-reduction of the chlorophyll content and enzyme activity in calvin cycle and finally it can reduce grow and yield of plant (Monakhova and Chernyadev, 2002). Chitosan categorized as a biotic elicitor in plants which activates gene expression for secondary metabolites, increasing of plant production, conservation of plant against microorganisms, seed germination and for growing in plants (Yin et al., 2011). The objective of this experiment was to investigate the effect of drought stress and chitosan application on physiological traits including photosynthetic pigments, proline, soluble sugars, and lipid peroxidation in T.deanensis in Shahrekord climate condition. Materials and methods In order to determine, the effect of drought stress and foliar application of chitosan on photosynthetic pigments, proline, soluble sugar, lipid peroxidation and cell membrane permeability of T. daenensis an experiment was conducted in Shahrekord climate in 2014. The experiment was laid out as factorial arrangement in complete randomized with three replications. Drought stress levels included well-watered (field capacity), irrigated daily to 50% field capacity (mild stress), and irrigated daily to 25% field capacity (severe stress), combined with three chitosan levels 0, 0.2, 0.4 g L-1 and acetic acid. At first seeds were planted in spring of 2014 in greenhouse conditions and then transferred in climate conditions. Chitosan was sprayed three times, just prior to flowering stage, at 50% flowering and at full flowering. Photosynthetic Pigments. Chlorophyll and carotenoid content was determined by Arnon method (1967). Proline. Proline concentration was measured by Bates et al., (1973). Leaf soluble sugars content. Soluble sugars content was determined by Fsles, (1951). Lipid peroxide (MDA). The lipid peroxidation level in plant tissues was determined in terms of MDA concentration (Robbert et al., 1980). Cell membrane permeability. Membrane permeability was determined by measuring (Lutts et al.,1998). Statistical analysis. SAS software and MSTATC were used for data analysis and means were compared using least significant difference. Results and discussion Photosynthetic pigments: The effect of drought stress had significantly (p≤0.01) on chlorophyll a. It seems that, when water stress intensified, activity of reactive oxidative species and chlorophylls’ enzyme increased. In general, foliar application of chitosan did not change on photosynthetic pigments. Proline: The effect of drought stress, chitosan and interaction between drought stress and chitosan had significantly (p≤0.01) on proline. When water stress intensified, proline increased. The highest proline content was obtained (3.85) µmol g-1 from severe stress and 0.4 g L-1 chitosan. By decreasing of water potential, the synthesis of proline from glutamic acid increased (Liang et al., 2013). Soluble Sugars: The interaction between drought stress and chitosan did not significant on soluble sugars but when water stress intensified, soluble sugars increased. Lipid peroxide (MDA content): The effect of drought stress, chitosan and interaction between drought stress and chitosan had significantly (p≤0.01) on lipid peroxide. In the study the effect of water stress on apple seedling, MDA content increased (Yang et al., 2009). In this study, spraying with 4 g L-1 chitosan could compensated damage caused by drought stress. Membrane permeability: The effect of drought stress and chitosan had significantly (p≤0.01) on membrane permeability. Conclusion Drought stress provokes ROS production in thyme plant, the compensatory effect of chitosan on reducing the negative impact of stressful conditions on plant was mainly due to stimulation of osmotic adjustment through proline accumulation, and reduction of lipid peroxidase level and therefore improvement of the integrity of cell membranes.
Hamid Reza Bagheri; Mohammad Hosein Gharineh; Abdolmehdi Bakhshandeh; Javad Taei; Abdolmohammad Mehnatkesh; Bahram Andarzian
Abstract
Introduction Potato (Solanum tuberosum L.) is one of the most important crops that plays a major role in feeding the world. The growing demand for potato, as both a fresh and processed food, along with the increase in world population, mean that yield will have to be improved through some combination ...
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Introduction Potato (Solanum tuberosum L.) is one of the most important crops that plays a major role in feeding the world. The growing demand for potato, as both a fresh and processed food, along with the increase in world population, mean that yield will have to be improved through some combination of germplasm enhancement, better crop protection and more efficient and productive management of irrigation and fertilization (Haase et al., 2007). Researches have proved potato is sensitive to drought stress at all stages of growth, especially at tuber formation stage due to reduction of leaf area and photosynthesis (Fabeiro et al., 2001; Ayas, 2013; Shock et al., 2013). Abiotic stress factors, such as drought, have severe, adverse effects on potato growth and yield. In particular, a regular water supply is necessary to achieve a high quality yield (Ierna and Mauromicale, 2006). In comparison with other species, potato is very sensitive to water stress because of its shallow root system (Ayas, 2013). Water shortage during tuber differentiation can delay growth and reduce earliness, whereas during tuber growth and bulking can decrease tuber size and have a drastic effect on yield (Alva et al., 2012; Liu et al.; 2006; Ayas, 2013). For processing potato, a careful N and water management is required to ensure regular growth, high dry matter content and marketable tubers (Shock et al., 1998; Zhang et al., 2006; Shahnazari et al., 2007). So this research was done to evaluate effects of different levels of water deficit and nitrogen fertilizer on tuber yield, yield components and water use efficiency of potato crop in Chahar Mahal va Bakhtiari province, in Iran. Materials and methods In order to study the effects of different levels of water deficit and nitrogen fertilizer on tuber yield and other agronomic traits of potato crop (Boren variety), a split plot experiment based on randomized complete block design, conducted at Chahar Mahal va Bakhtiari Research Center of Agriculture and Natural Resources, in 2013. The levels of water deficit were S1, S2 and S3 (100, 75 and 50% of the water requirement of potato crop after emergence by the end of the growing season, respectively), as the main plots and nitrogen fertilizer treatments were N1, N2, N3 and N4 (100, 66, 33 percent of plant nitrogen requirement and without nitrogen consumption, respectively) as sub plots. Results and discussion In this experiment water deficit had decreasing effect on tubers dry matter percent but nitrogen changes had no distinct effect on this trait. By applying water deficit and decreased levels of nitrogen, the number of tubers per plant and the average tubers weight also fell. The greatest and the lowest number of tubers per plant were seen at S1 and S3 treatments (8.4 and 7.4 respectively). The maximum weight of tubers observed at full irrigation treatment (118 g) that had no significant difference with S2, but at treatment S3 (50% of the water requirement), tubers were produced lighter with an average weight of 86.6 grams. So it can be concluded, in this irrigation regime, the average weight of tubers is closer to weight of seed tuber class. Many studies have confirmed these findings (Fabeiro et al., 2001; Ayas and Korukcu, 2010; Ayas, 2013). The results showed that maximum tuber yield gained from S1 treatment (55.9 ton/ha) that had no significant difference with S2, but intensive drought stress (S3) produced minimum tuber yield (31.7 ton/ha). N1 and N2 treatments led to highest tuber yield but the lack of nitrogen (N4) caused the lowest tuber yield (38.7 ton/ha). Generally, in S2 and S3 drought stress levels, N2 produced maximum tuber yield. The reduction of tuber yield in S2 and S3 treatments within increment of nitrogen consumption (N1), caused the significant interaction between drought stress and nitrogen on tuber yield. Ierna and Mauromicale (2006) reported that water deficit stress as much as 50% of the water requirement, had increased stomatal resistance and caused the reduction of leaves photosynthesis, biomass, tuber growth and tuber yield. Demelash, 2013; Alva et al., 2012 and Ayas, 2013 studies also confirm the results of this Research. The second level of nitrogen (N2) in S3 treatments led to maximum, but S1N4 led to minimum water use efficiency (9.21 and 5.24 kg/m3 respectively). Liu et al. (2006) reported, by reducing the amount of irrigation volume, tuber yield decreases baut water use efficiency will increase.The stepwise regression analysis showed that the average tuber weight explains most changes of marketable tuber yield per plot. Conclusions Based on the results of the present study, since there is no statistical difference in tuber yield, between S1 and S2 irrigation regimes, it is recommended that for proper utilization of water resources and achieve economic yield, potato crop, produce with 6400 m3 water per hectare with irrigation at 7 days period. Results showed, at S2 irrigation regime, N2 Treatment (consumption of 270 kg Urea/ ha) had produced the highest yield, so S2N2 treatments is the best option for potato crop production.
