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Background: Research on the submergence stress of rice has concentrated on the quiescence strategy to survive in long-term flooding conditions based on Submergence-1A (SUB1A). In the case of the ripening period, it is important that submergence stress can affect the quality as well as the survival of rice. Therefore, it is essential to understand the changes in the distribution of assimilation products in grain and ripening characteristics in submergence stress conditions. However, such studies have been insufficient at the physiological and molecular biological levels. Results: We confirmed that the distribution rate of assimilation products in grain was decreased by submergence treatment. These results were caused by an increase in the distribution rate of assimilation products to the stem according to escape strategy. To understand this phenomenon at the molecular level, we analyzed the relative expression levels of genes related to sucrose metabolism, and found that the sucrose phosphate synthase gene (OsSPS), which induces the accumulation of sucrose in tissues, was decreased in the seeds and leaves, but not in the stems. Furthermore, the sucrose transporter gene (OsSUT) related to sucrose transport decreased in the seeds and leaves, but increased in stems. We also analyzed the biological metabolic processes related to starch and sucrose synthesis, carbon fixation, and glycolysis using the KEGG mapper with selected differentially expressed genes (DEGs) in seeds, stems, and leaves caused by submergence treatment. We found that the expression of genes for each step related to starch and D-glucose synthesis was down-regulated in the seeds and leaves but up-regulated in the stem. Conclusion: The results of this study provide basic data for the development of varieties and corresponding technologies adapted to submergence conditions, through understanding the action network of the elements that change in the submergence condition, as well as information regarding useful DEGs. [ABSTRACT FROM AUTHOR]

In modern agriculture, mepiquat chloride (pix) as a synthetic growth regulator, is considered as an important management tool for reducing stress damage in Cotton seed. In the present study, the effects of the growth regulator, pix were investigated on the physiological and biochemical characteristics in new cultivars of cotton in response to salinity stress in Golestan province, Iran. The experiment was carried out in a completely randomized design enriched with 10 gr. L-1 Pix and 15 ds.m-1 salt (sodium chloride) in Petri dish with three cultivars (Latif, Kashmar and Sahel). The physiological and biochemical parameters of seedlings were measured after 4 days. The use of Pix in saline conditions resulted in a significant increase in germination percentage, radicle length, dry and fresh weights, phenolic compounds, as well as proline and glycine betaine content in the Latif and Kashmar cultivars (p ≤ 0.05). The amount of Na+ ion absorption was lower in Kashmar and Latif cultivars compared with the Sahel cultivar while the amount of K+ and Ca2+ ions absorption was increased in the two mentioned cultivars compared to the Sahel cultivar. This study showed that the effects of stress were reduced after treating the seeds with Pix, especially in the Kashmar and Latif cultivars during the seedling stage. [ABSTRACT FROM AUTHOR]

[Objective] The present paper aims to reveal the changes of Cd absorption and free amino acids in sugarcane under the stress of cadmium (Cd) , and to provide a basis for further study of the tolerance mechanism of sugarcane on Cd stress. [Method JCd uptake and the changes of sugarcane free amino acids were determined by amino acid analyzer and Atomic fluorescence spectrometer with different Cd concentration^, 25, 50, 100 mg/kg) under potted conditions. [Result] It was found that the toxic symptoms of sugarcane increased with the increasing of Cd concentration, the Cd content in sugarcane stems and sugarcane leaves increased with the increasing of Cd concentration, and showed a significant positive correlation; the content of Arg and Leu increased with the increase of Cd concentration. The amino acids such as Asp and Glu decreased as the concentration of Cd treatment was 25 rng/kg and then increased w ith the increasing of Cd concentration. [Conclusion] Cd content in stems and leaves of sugarcane were significantly increased and 17 kinds of free amino acids content were changed under Cd stress. [ABSTRACT FROM AUTHOR]

In the era present, due to increasing incidences of a large number of different biotic and abiotic stresses all over the world, the growth of plants (principal crops) may be restrained by these stresses. In addition to beneficial microorganisms, use of silicon (Si)-fertilizer is known as an ecologically compatible and environmentally friendly technique to stimulate plant growth, alleviate various biotic and abiotic stresses in plants, and enhance the plant resistance to multiple stresses, because Si is not harmful, corrosive, and polluting to plants when presents in excess. Here, we reviewed the action mechanisms by which Si alleviates abiotic and biotic stresses in plants. The use of Si (mostly as industrial slags and rice straw) is predicted to become a sustainable strategy and an emerging trend in agriculture to enhance crop growth and alleviate abiotic and biotic stresses in the not too distant future. In this review article, the future research needs on the use of Si under the conditions of abiotic and biotic stresses are also highlighted. [ABSTRACT FROM AUTHOR]

To determine the parameters of Modified Cam-Clay model for paddy grain, a constitutive stress-strain equation, was used to study the stress-strain behavior of paddy grain. Triaxial tests were carried out four different moisture contents of paddy. This elastoplastic model contains five parameters: the critical state ratio M , the logarithmic hardening modulus λ , the isotropic swelling index κ , the elastic modulus E and the Poisson’s ratio ν , which can be evaluated in axial compression test and the isotropic compression test. The experimental results reveal that the M of paddy grain (Xiandao 118) with four different moisture contents (11.75%, 13.34%, 14.93% and 16.43%w.b.) were 2.1195, 2.1093, 2.0931 and 2.0110, the λ were 0.1408, 0.1390, 0.1355 and 0.1304, the κ were 0.1018, 0.0935, 0.0986 and 0.0948, and the ν were 0.145, 0.152, 0.155 and 0.166, respectively. The relation equations between the elastic modulus E with generalized shearing force q and mean principal stress p were obtained from the analysis of the experimental results. The comparisons between the Modified Cam-Clay model calculated values and measured values showed that the calculated parameters of the Modified Cam-Clay model are reasonable and the model can adequately describe the stress-strain behavior of paddy grain for the conditions tested. [ABSTRACT FROM AUTHOR]

There is a very effective cross-talk between signals triggered by reactive oxygen species and hormonal responses in plants, activating proteins/enzymes likely to be involved in stress tolerance. Abscisic acid (ABA) is known as a stress hormone that takes part in the integration of signals. This work aimed to characterize the biochemical response and ultrastructural changes induced by cadmium (Cd) in the Micro-Tom (MT) sitiens ABA-deficient mutant ( sit) and its wild-type (MT) counterpart. MT and sit plants were grown over a 96-h period in the presence of Cd (0, 10, and 100 μM CdCl). The overall results indicated increases in lipid peroxidation, hydrogen peroxide content and in the activities of the key antioxidant enzymes such as catalase, glutathione reductase, and ascorbate peroxidase in both genotypes. On the other hand, no alteration was observed in chlorophyll content, while the activity of another antioxidant enzyme, superoxide dismutase, remained constant or even decreased in the presence of Cd. Roots and shoots of the sit mutant and MT were analyzed by light and transmission electron microscopy in order to characterize the structural changes caused by the exposure to this metal. Cd caused a decrease in intercellular spaces in shoots and a decrease in cell size in roots of both genotypes. In leaves, Cd affected organelle shape and internal organization of the thylakoid membranes, whereas noticeable increase in the number of mitochondria and vacuoles in MT and sit roots were observed. These results add new information that should help unravel the relative importance of ABA in regulating the cell responses to stressful conditions induced by Cd apart from providing the first characterization of this mutant to oxidative stress. [ABSTRACT FROM AUTHOR]

Indian mustard [ Brassica juncea (L.) Czern & Coss.] is one of the most important oilseed crop worldwide, yet relatively mild drought and salinity stress significantly reduce its growth and yield. Expression of LEA (Late Embryogenesis Abundant) proteins was previously shown to alleviate osmotic stress by stabilizing water status, protecting cytosolic structures and cell through increased membrane and protein stability. We overexpressed Arabidopsis group 4 LEA protein At LEA4-1 in mustard, resulting the transgenic lines to show enhanced drought and salinity tolerance. Southern hybridization showed the copy number of the gene inserted into the transgenics while, qRT PCR determined the transcript level of the overexpressed gene. Leaf senescence assay showed better adaptability of the transgenics to both salt and PEG stress, as revealed by increased chlorophyll content in the transgenic plants when compared to wild type. The transgenic mustard plants showed better survivability under both drought and salinity stress in soil. Physiological analysis revealed lower levels of lipid peroxidation, hydrogen peroxide and oxygen radical production but higher levels of relative water content (RWC) in T 1 transgenic AtLEA4-1 lines with not so significant increase in proline content. Antioxidative enzyme activities showed better adaptation of transgenic plants to drought stress. Even when the biochemical parameters were analysed as a function of RWC, the transgenic plant tissues showed improved adaptation to drought and salinity stress depicting, the functions of LEA proteins as antioxidant and molecular chaperone exerting equivalent impact as that of hydration buffer towards abiotic stress tolerance. [ABSTRACT FROM AUTHOR]

Rice belongs to tropical and subtropical environments and is extremely sensitive to chilling stress particularly during emergence and early stages of seedling development. Seed priming can be a good approach to enhance rice germination and stand establishment under chilling stress. The present study examined the role of different seed priming techniques viz., hydropriming, osmopriming, redox priming, chemical priming, and hormonal priming, in enhancing the chilling tolerance in rice. The most effective reagents and their pre-optimized concentrations based on preliminary experiments were used in this study. Two different rice cultivars were sown under chilling stress (18?C) and normal temperatures (28?C) in separate growth chambers. A nonprimed control treatment was also maintained for comparison. Chilling stress caused erratic and delayed germination, poor seedling growth, reduced starch metabolism, and lower respiration rate, while higher lipid peroxidation and hydrogen peroxide accumulation in rice seedlings of both cultivars. Nevertheless, all the seed priming treatments effectively alleviated the negative effects of chilling stress. In addition, seed priming treatments triggered the activities of superoxide dismutase, peroxidase, and catalase, and enhanced the accumulations of glutathione and free proline in rice seedlings, which suggests that these measures help prevent the rice seedlings from chilling induced oxidative stress. Chemical priming with selenium and hormonal priming with salicylic acid remained more effective treatments for both rice cultivars under chilling stress than all other priming treatments. The better performance and greater tolerance of primed rice seedlings was associated with enhanced starch metabolism, high respiration rate, lower lipid peroxidation, and strong antioxidative defense system under chilling stress. [ABSTRACT FROM AUTHOR]

Diazinon insecticide is widely applied throughout rice ( Oryza sativa L.) fields in Iran. However, concerns are now being raised about its potential adverse impacts on rice fields. In this study, a time-course metabolic change in rice plants was investigated after diazinon treatment using gas chromatography–mass spectrometry (GC–MS), and subsequently the statistical strategy of random forest (RF) was performed in order to find the stress-associated effects. According to the results, a wide range of metabolites were dynamically varied as a result of the plant response to diazinon such as biosynthesis and metabolism of sugars, amino acids, organic acids, and phenylpropanoids, all correlating with the exposure time. Plant response was involved in multiple metabolic pathways, most of which were correlated with the exposure time. In this study, RF was explored as a potential multivariate method for GC–MS analysis of metabolomics data of rice ( O. sativa L.) plants under diazinon stress; more than 31 metabolites were quantitatively determined, and time-course metabolic response of the plant during different days after treatment was measured. Results demonstrated RF as a potential multivariate method for GC–MS analysis of changes in plant metabolome under insecticide stress. [ABSTRACT FROM AUTHOR]

A two-years experiment was carried out under controlled conditions in the greenhouse of Wheat Research Department, Field Crops Research Institute, Agricultural Research Center (ARC), Giza, Egypt in 2010/2011 and 2011/2012 growing seasons. Orie hundred and twenty five doubled haploid regenerated bread wheat lines derived from the cross between Sakha 8 cultivar (salt tolerant) and Line 25 (salt sensitive) were investigated. The two parents and the three cultivars Giza 168, Sakha 93 and Sids 1 were used as checks. Seeds were sown in thoroughly washed sandy pots of 30-cm diameter, under 9000 mg L-1 salinity level in irrigation water besides the control. The experiment comprised 520 pots, which has 130 genotypes at two salinity levels in two replications. A split plot design in a randomized complete block arrangement was used. Germinated seeds were counted 20 days after sowing. Seedling height, grain and biological weight per plant were recorded as well. Combined results across seasons showed that the tested lines and cultivars significantly differed in germination percentage, grain weight plant-1 and biomass plant-1 but did not differ in seedling height. Salinity level of 9000 mg L-1 NaCl significantly decreased those traits compared to the control by 56,5, 61.5 and 56.5%, respectively. The interaction between line and salinity level significantly affected germination percentage, grain weight plant-1 and biomass plant-1. However, it had no effect on seedling height. [ABSTRACT FROM AUTHOR]

Peanut ( Arachis hypogaea L.), as a source of oil and protein, is the second-most important grain legume cultivated in the world. Peanut is a relatively drought-tolerant crop; however, the molecular biology research of peanut is far behind other crops; the molecular mechanisms of its stress resistance are poorly understood. DELLA proteins, negative regulators of gibberellin signaling pathway in plants, promote survival of plants in adverse environments. In this study, four DELLA homologue genes were isolated using peanut transcriptome sequences. Molecular phylogenetic analysis revealed that these four AhDELLAs fall into three distinct groups: AhDELLA1 and AhDELLA2 clustered into two distinct groups, while AhDELLA3 and AhDELLA4 were in one group, which was separated from other DELLAs. qRT-PCR results showed that these four DELLA genes were expressed differentially in various peanut tissues. The AhDELLA1 and AhDELLA2 genes were expressed ubiquitously in different tissues. AhDELLA3 and AhDELLA4 showed much higher expression level in flowers and seeds as compared with other organs. The expression of four AhDELLA genes was temporally induced by PEG 6000 treatment. The AhDELLA3 and AhDELLA4 transcripts were significantly induced by NaCl treatment, while the expression of AhDELLA1 and AhDELLA2 did not change much under salt stress. The possible role of DELLA proteins in peanut development and responses to abiotic stresses is discussed. [ABSTRACT FROM AUTHOR]

The effects of chilling-light stress combined with additional stress on PSI and PSII photoinhibition and their interrelationship have not been known. To explore whether NaCl affects the PSI and PSII photoinhibition and their interrelationship under chilling-light treatment, the PSI and PSII activities were studied under chilling-light with or without NaCl treatment. The results showed that the extent of PSI and PSII photoinhibition both increased under chilling-light, while NaCl aggravated PSII photoinhibition and severely damaged cytochrome b 6 /f complex but alleviated PSI photoinhibition. Moreover, DCMU had a similar effect as NaCl in this study, which indicates that NaCl alleviated PSI photoinhibition through reducing electrons transported to PSI. It was also showed that the increased damage to PSII by NaCl did not depend on the inhibition of PSII repair and PSI electron transportation. In conclusion, NaCl alleviated PSI photoinhibition by inhibiting electron transport from PSII under chilling-light conditions. In addition, PSII photoinhibition was not affected by PSI photoinhibition because of a full inhibition of PSII repair by chilling-light treatment. We also speculate that NaCl aggravates PSII photoinhibition by enhancing the damage instead of inhibiting the repair of it under chilling-light conditions. [ABSTRACT FROM AUTHOR]

Abstract: The majority of common bean plants are cultivated under drought conditions. Maintaining crop yields under drought stress is thus one of the biggest challenges facing bean production. In order to improve our understanding of the complex mechanisms involved in the response of common bean (Phaseolus vulgaris) to drought stress, a proteomic approach was used to identify drought-responsive proteins in leaves of two cultivars differing in their response to drought, Tiber and more sensitive Starozagorski čern. 2D-DIGE was used to compare differences in protein abundance between control and stressed plants. Fifty-eight proteins whose abundance changed significantly were identified by LC-MS/MS in Tiber and 64 in Starozagorski čern. The majority of identified proteins were classified into functional categories that include energy metabolism, photosynthesis, ATP interconversion, protein synthesis and proteolysis, stress and defence related proteins. Details of the function of the identified proteins and their abundance profiles in Tiber and Starozagorski are discussed. Interactions between identified proteins were demonstrated by bioinformatics analysis, enabling a more complete insight into biological pathways and molecular functions affected by drought stress. The results form the basis for a further understanding of the biochemical mechanisms of drought response in common bean. [Copyright &y& Elsevier]

Sea urchin gonads also known as roe or uni are a high-valued food, considered a delicacy in many parts of the world. To determine the impact of stress caused by exposure of live urchins to air on the subsequent shelf-life of recovered gonads, urchins ( Evechinus chloroticus) were held in air at either 4 °C for 144 h or 15 °C for 72h. The coelomic fluid of urchins held in air showed a decrease in pH and increase in lactic acid concentration, percentage solid, turbidity level, colour and coelomocyte numbers. Gonads recovered from urchins held in air exhibited enhanced rates of deterioration over time, as assessed by a loss of surface definition and a decrease in their water-holding capacity and height-to-surface ratio (melting). Gonad deterioration was minimised by implementing a brine + alum wash upon immediate removal of gonads from live urchins. This research has shown that the manner in which live urchins are held and processed has a dramatic impact on the subsequent shelf-life and quality of the recovered gonads. [ABSTRACT FROM AUTHOR]

Although the functional roles of glycine-rich RNA-binding proteins (GRPs) during stress adaptation have been extensively evaluated in Arabidopsis thaliana and rice ( Oryza sativa), the stress-responsive roles of a majority of GRPs have not been characterized in other plant species including rapeseed ( Brassica napus). Here, the characteristic features and stress-responsive expression patterns of GRPs in B. napus (BnGRPs) were investigated. The genome of B. napus contains seven closely related BnGRPs, where the amino acid sequences of a well-conserved RNA-recognition motif at the N-terminal region are highly similar to each other but the sequences of the C-terminal glycine-rich region vary greatly among different BnGRPs. The transcript levels of all BnGRPs were markedly upregulated by cold stress, while their expression was significantly downregulated by dehydration or high salinity stress. Among the seven BnGRPs evaluated, BnGRP1 was characterized in more detail for its cellular localization and functional role as an RNA chaperone under cold stress. Cold-induced BnGRP1 successfully complemented the cold-sensitive phenotype of Escherichia coli mutant BX04 cells under cold stress, and harbored DNA- and RNA-melting abilities. Ectopic expression of BnGRP1 in Arabidopsis resulted in accelerated seed germination and enhanced freezing tolerance of the plant under cold or freezing stress. Collectively, the results of this study support the emerging idea that GRPs are functionally conserved RNA chaperones during the cold adaptation process in diverse plant species. [ABSTRACT FROM AUTHOR]

A large proportion of the worlds' wheat growing regions suffers water and/or heat stress at some stage during the crop growth cycle. With few exceptions, there has been no utilisation of managed environments to screen mapping populations under repeatable abiotic stress conditions, such as the facilities developed by the International Wheat and Maize Improvement Centre (CIMMYT). Through careful management of irrigation and sowing date over three consecutive seasons, repeatable heat, drought and high yield potential conditions were imposed on the RAC875/Kukri doubled haploid population to identify genetic loci for grain yield, yield components and key morpho-physiological traits under these conditions. Two of the detected quantitative trait loci (QTL) were located on chromosome 3B and had a large effect on canopy temperature and grain yield, accounting for up to 22 % of the variance for these traits. The locus on chromosome arm 3BL was detected under all three treatments but had its largest effect under the heat stress conditions, with the RAC875 allele increasing grain yield by 131 kg ha (or phenotypically, 7 % of treatment average). Only two of the eight yield QTL detected in the current study (including linkage groups 3A, 3D, 4D 5B and 7A) were previously detected in the RAC875/Kukri doubled haploid population; and there were also different yield components driving grain yield. A number of discussion points are raised to understand differences between the Mexican and southern Australian production environments and explain the lack of correlation between the datasets. The two key QTL detected on chromosome 3B in the present study are candidates for further genetic dissection and development of molecular markers. [ABSTRACT FROM AUTHOR]

Increased incidences of abiotic and biotic stresses impacting productivity in principal crops are being witnessed all over the world. Extreme events like prolonged droughts, intense rains and flooding, heat waves and frost damages are likely to further increase in future due to climate change. A wide range of adaptations and mitigation strategies are required to cope with such impacts. Efficient resource management and crop/livestock improvement for evolving better breeds can help to overcome abiotic stresses to some extent. However, such strategies being long drawn and cost intensive, there is a need to develop simple and low cost biological methods for the management of abiotic stress, which can be used on short term basis. Microorganisms could play a significant role in this respect, if we can exploit their unique properties of tolerance to extremities, their ubiquity, genetic diversity, their interaction with crop plants and develop methods for their successful deployment in agriculture production. Besides influencing the physico-chemical properties of rhizospheric soil through production of exopolysaccharides and formation of biofilm, microorganisms can also influence higher plants response to abiotic stresses like drought, chilling injury, salinity, metal toxicity and high temperature, through different mechanisms like induction of osmo-protectants and heat shock proteins etc. in plant cells. Use of these microorganisms per se can alleviate stresses in crop plants thus opening a new and emerging application in agriculture. These microbes also provide excellent models for understanding the stress tolerance, adaptation and response mechanisms that can be subsequently engineered into crop plants to cope with climate change induced stresses. [ABSTRACT FROM AUTHOR]

The yield of 186 F barley breeding lines, under stress and non-stress conditions, utilizing four stress indices: S (stress susceptibility index); P (yield deviation between genotype and best genotype in given environment); b (regression coefficient) and PCA (principal component analysis) scores, was investigated in an experiment carried out at the Agricultural Research Station of the Field Crop Institute of Sétif (Algeria). The results indicated significant differences between lines, with a grain yield mean ranging from 127.3 to 1246.6 g m over the four cropping seasons and a genotype × environment variance component 1.83 higher than the genotypic variance component. S index identified divergent plant material under stressed and unstressed environments. Yield differential between lines with high and low S index was large, limiting the use of the S index to compromise between high yield and adaptability. Lines with low S values are high yielding under stress but are less responsive when growing conditions improve. Low P index identified lines with high yield in the unstressed environment and poor yield under stress conditions, while high P identified lines performing poorly in both environments, suggesting that P index was able to integrate both yield potential and yield stability. Lines with a slope b < 1 showed similar grain yield as those with high P or low S values. Lines with of slope b = 1 have average yield, and as such combine average yield, adaptability and stress resistance. Because of their close mutual relationships, the indices were represented by the first principal component of the PCA, suggesting that PC (principal component) scores would be more appropriate to integrate yield potential and adaptation to variable environments. [ABSTRACT FROM AUTHOR]

Abstract: The response of the antioxidant enzymes, superoxide dismutase (SOD; EC 1.15.1.1) and peroxidase (POD; EC 1.11.1.7), to Aluminum (Al) stress was studied in roots of two inbred lines of maize (Zea mays L.) differing in their tolerance to Al. In addition, the production of malondialdehyde (MDA) was measured to evaluate the level of lipid peroxidation as well as the accumulation of proline (Pro) and carbohydrates under 72h Al stress. Roots of Al (0, 120, 240, 360 and 480μM, at pH 4.2) -treated plants were sampled at various times (12, 24, 48, 72h) after commencement of stress. A major difference in the antioxidant enzymes between the two maize lines associated with Al tolerance was observed after 24h of Al exposure. A gradual increase in the membrane lipid peroxidation in Al-stressed root of the susceptible maize line was accompanied by decreased activities of the antioxidant enzymes SOD and POD. In contrast, increased activities of the SOD and POD were found in Al-treated roots of the tolerant maize line, in which the level of membrane lipid peroxidation remained almost unchanged. After 72h exposure to 480μM Al the accumulation of Al in roots was almost from 90 times (tolerant) to 140 times (sensitive) than the control (without Al), while at the same time Al treatment resulted in 2.2 to 2.5-fold (at 240, 360 and 480μM Al) increased Pro content in the roots of the tolerant line compared to 0μM Al. Yet, 72h exposure to 480μM Al increased 1.7-fold the carbohydrate concentration in the roots of the Al tolerant maize line VA-22 while in the sensitive line A4/67 remained almost unchanged. These data provide evidence of an internal mechanism of tolerance that increase the antioxidant system activity in order to limit cellular damages and possibly linked to the Al tolerance of the maize line VA-22. Analyses of the 12, 24, 48, and 72h POD and SOD isoforms showed that in the Al-tolerant maize plants the anionic POD isoforms A1, A3 and A4 and the SOD isoforms SOD1 and SOD2 were induced by increased Al-stress. It seemed that in the Al tolerant maize line, the anionic POD isoforms A1, A3 and A4 and the SOD isoforms SOD1 and SOD2 were required for adaptation as the oxidant level increased by the increased Al stress. Our results suggest that Al toxicity may be mediated by oxidative stress and that the better protection of the Al tolerant maize roots from Al-induced oxidative damage results, at least partially, from the increased activity of their antioxidative system. [Copyright &y& Elsevier]

Abstract: In this study, the possibility of enhancing chilling stress tolerance of pepper (Capsicum annuum L.) during early growth stages by exogenous application of 5-aminolevulinic acid (ALA) was investigated. To improve chilling tolerance during seedling stage, ALA was applied in various concentrations (0, 1, 10, 25 and 50ppm) through three different methods (seed soaking, foliar spray, or soil drench). After ALA applications, the plants were subjected to chilling stress at 3°C for 2 days. Although all ALA application methods improved chilling stress tolerance in pepper seedlings, seed soaking and foliar spray provided better protection against chilling stress compared to soil drench. Exogenous application of ALA provided significant protection against chilling stress compared to non-ALA-treated seedlings, significantly enhancing plant mass and chlorophyll, sucrose, and proline contents. ALA pre-treatment also increased relative water content, stomatal conductance and superoxide dismutase (SOD) enzyme activity and reduced membrane permeability. Of the ALA concentrations, the highest chilling tolerance was obtained with 25ppm ALA pre-treatment. Results indicate that ALA which is considered as an endogenous plant growth regulator could be used effectively to protect pepper seedlings from damaging effects of chilling stress without any adverse effect on seedling growth. [Copyright &y& Elsevier]

Rice is the principle staple crop of Asia and any deterioration of rice production systems through climate change would seriously impair food security in this continent. This review assesses spatial and temporal vulnerabilities of different rice production systems to climate change impacts in Asia. Initially, the review discusses the risks of increasing heat stress and maps the regions where current temperatures are already approaching critical levels during the susceptible stages of the rice plant, namely Pakistan/north India (Oct.), south India (April, Aug.), east India/Bangladesh (March-June), Myanmar/Thailand/Laos/Cambodia (March-June), Vietnam (April/Aug.), Philippines (April/June), Indonesia (Aug.) and China (July/Aug.). Possible adaptation options for heat stress are derived from regions where the rice crop is already exposed to very high temperatures including Iran and Australia. Drought stress is also expected to aggravate through climate change; a map superimposing the distribution of rainfed rice and precipitation anomalies in Asia highlights especially vulnerable areas in east India/ Bangladesh and Myanmar/Thailand. Then, the review gives emphasis to two rice growing environments that have outstanding importance for food supply in Asia and, at the same time, are particularly vulnerable to climate impacts. The mega-deltas in Vietnam, Myanmar and Bangladesh are the backbone of the rice economy in the respective country and will experience specific climate change impacts due to sea level rise. Significant improvements of the rice production systems, that is, higher resilience to flooding and salinity, are crucial for maintaining or even increasing yield levels in these very productive deltaic regions. The other 'hotspot' with especially high climate change risks in Asia is the Indo-Gangetic Plains (IGP) which will be affected by the melting of the Himalayan glaciers. The dominant land use type in the IGP is rice-wheat rotation, and we discuss specific vulnerabilities and possible adaptation options in the different sub-regions of the IGP. We conclude that geo-spatial vulnerability assessments may become crucial for planning targeted adaptation programs, but that policy frameworks are needed for their implementation. [ABSTRACT FROM AUTHOR]

Solanum tuberosum is a frost-sensitive species incapable of cold acclimation. A brief exposure to frost can significantly reduce its yields, while hard frosts can completely destroy entire crops. Thus, gains in freezing tolerance of even a few degrees would be of considerable benefit relative to frost damage. The S. tuberosum cv. Umatilla was transformed with three Arabidopsis CBF genes ( AtCBF1-3) driven by either a constitutive CaMV35S or a stress-inducible Arabidopsis rd29A promoter. AtCBF1 and AtCBF3 over-expression via the 35S promoter increased freezing tolerance about 2 °C, whereas AtCBF2 over-expression failed to increase freezing tolerance. Transgenic plants of AtCBF1 and AtCBF3 driven by the rd29A promoter reached the same level of freezing tolerance as the 35S versions within a few hours of exposure to low but non-freezing temperatures. Constitutive expression of AtCBF genes was associated with negative phenotypes, including smaller leaves, stunted plants, delayed flowering, and reduction or lack of tuber production. While imparting the same degree of freezing tolerance, control of AtCBF expression via the stress-inducible promoter ameliorated these negative phenotypic effects and restored tuber production to levels similar to wild-type plants. These results suggest that use of a stress-inducible promoter to direct CBF transgene expression can yield significant gains in freezing tolerance without negatively impacting agronomically important traits in potato. [ABSTRACT FROM AUTHOR]

C-repeat/dehydration-responsive element binding factors (CBF/DREBs) are a family of transcription factors that regulate freezing tolerance in Arabidopsis. As a step towards understanding the stress response of monocotyledonous plants, we isolated a barley gene HvCBF4 whose expression is induced by low-temperature stress. Transgenic over-expression of HvCBF4 in rice resulted in an increase in tolerance to drought, high-salinity and low-temperature stresses without stunting growth. Interestingly, under low-temperature conditions, the maximum photochemical efficiency of photosystem II in the dark-adapted state ( Fv/ Fm, where Fv is the variable fluorescence and Fm is the maximum fluorescence) in HvCBF4 plants was higher by 20% and 10% than that in non-transgenic and CBF3/DREB1A plants, respectively. Using the 60K Rice Whole Genome microarray, 15 rice genes were identified that were activated by HvCBF4. When compared with 12 target rice genes of CBF3/DREB1A, five genes were common to both HvCBF4 and CBF3/DREB1A, and 10 and seven genes were specific to HvCBF4 and CBF3/DREB1A, respectively. Interestingly, HvCBF4 did not activate Dip1 and Lip5, two important target genes of CBF3/DREB1A, in transgenic rice under normal growth conditions, but their expression was enhanced by HvCBF4 under low-temperature conditions. Our results suggest that CBF/DREBs of barley act differently from those of Arabidopsis in transgenic rice. [ABSTRACT FROM AUTHOR]

This review concerns ear photosynthesis and its contribution to grain filling in C3 cereals. Ear photosynthesis is quantitatively important to grain filling, particularly in dry areas where source (i.e., assimilate) limitations can occur. Compared to the flag leaf, ear photosynthesis exhibits higher water stress tolerance. Several factors could be involved in the ear's “drought tolerance.” First, although degree of C4 metabolism in ear parts has been reported, current evidence supports only typical C3 metabolism. Second, recycling of respired CO2 (i.e., refixation) could have considerable impact on final crop yield by preventing loss of CO2. Because refixation of CO2 is independent of atmospheric conditions, water use efficiency (measured as total ear photosynthesis divided by transpiration) could be higher in the ear than in the flag leaf. Moreover, ear parts (in particular awns) show higher relative water content and better osmotic adjustment under water stress compared to the flag leaf. This capacity, in addition to persistence of photosynthetic components under drought (delayed senescence), might help the ear to continue to fix CO2 late in the grain filling period. [ABSTRACT FROM AUTHOR]

This study was to test the hypothesis that the interaction between abscisic acid (ABA) and ethylene may be involved in mediating the effects of water stress on grain filling. Two high lodging-resistant rice ( Oryza sativa L.) cultivars were pot-grown. Three treatments, well-watered, moderate water-stressed (MD), and severe water-stressed (SD), were imposed from 9 d post-anthesis until maturity. Grain filling rate and grain weight were significantly increased under MD but decreased under SD. The two cultivars behaved the same. ABA concentration in the grains was very low during the grain filling stage, reaching a maximum when the grain filling rate was highest. Both the grain filling rate and ABA concentration were substantially enhanced by water stress. In contrast to ABA, concentrations of ethylene and 1-aminocylopropane -1-carboxylic acid (ACC) in the grains were very high at early grain filling stage and sharply decreased during the linear period of grain growth. MD reduced, whereas SD remarkably increased, their accumulation. The ratio of ABA to ACC was increased in MD grains but decreased in SD grains, indicating that there was a greater enhancement of ABA concentration than ethylene production in the MD treatment only. Application of cobalt ion (inhibitor of ethylene synthesis) or ABA at the early grain filling stage significantly increased grain filling rate. Spraying with ethephon (ethylene-releasing agent) or fluridone (inhibitor of ABA synthesis) had the opposite effect. The results suggest that antagonistic interactions between ABA and ethylene mediate the grain filling rate, and a high ratio of ABA to ethylene enhances grain filling rate. [ABSTRACT FROM AUTHOR]

Over a period of two years greenhouse experiments were carried out to quantify the interaction ozone exposure × water stress in winter wheat (Triticum aestivum L. cv. Perlo). Assessment of effects carried out on various yield parameters showed that abundant water supply made the plants most sensitive to ozone exposure. In well-watered plants (75%} of soil water capacity, s.w.c.), the AOT40 ozone exposure doses of 26.8 and 24.9 μmol mol-1 hr-1 (ppm.h) caused grain yield reductions by 35 and 39%. No reductions of yields were observed at severe water stress (35% of s.w.c.) condition. The decrease in ozone responsiveness under drought can be explained by a distinct reduction in ozone uptake (18 vs. 2 mmol m-2 in well-watered vs. severely stressed plants at the same ozone exposure). The calculations of ozone uptake were based on repeated measurements of leaf conductance. Generally curvi-linear regression functions explained the dependence of relative yield on ozone and on water stress better than multiple simple linear regression functions. The consideration of ozone uptake instead of ozone exposure improved the performances of the models further. For explaining grain yield, 96.8% of the variances could be explained by a model resulting from curvi-linear regression fitting. A suggestion for calculating correction factors to modify critical levels in the case of limited water supply is presented. [ABSTRACT FROM AUTHOR]

The antioxidant composition and relative water stress tolerance of nodulated alfalfa plants (Medicago sativa L. × Sinorhizobium meliloti 102F78) of the elite genotype N4 and three derived transgenic lines have been studied in detail. These transgenic lines overproduced, respectively, Mn-containing superoxide dismutase (SOD) in the mitochondria of leaves and nodules, MnSOD in the chloroplasts, and FeSOD in the chloroplasts. In general for all lines, water stress caused moderate decreases in MnSOD and FeSOD activities in both leaves and nodules, but had distinct tissue-dependent effects on the activities of the peroxide-scavenging enzymes. During water stress, with a few exceptions, ascorbate peroxidase and catalase activities increased moderately in leaves but decreased in nodules. At mild water stress, transgenic lines showed, on average, 20% higher photosynthetic activity than the parental line, which suggests a superior tolerance of transgenic plants under these conditions. However, the untransformed and the transgenic plants performed similarly during moderate and severe water stress and recovery with respect to important markers of metabolic activity and of oxidative stress in leaves and nodules. We conclude that the base genotype used for transformation and the background SOD isozymic composition may have a profound effect on the relative tolerance of the transgenic lines to abiotic stress. [ABSTRACT FROM AUTHOR]

Temperature is often pointed out as the major factor in determining the bacterial community diversity and has a marked influence on survival and persistence of rhizobial stains in soils. Rhizobial strains obtained from different red clover and alfalfa varieties were examined for their ability to survive under different temperature levels on two different media. Rhizobial isolates either increased or remained constant as estimated by plate count at 20 and 35°C. Significant reduction was detected at 4, 10, 15 and 42°C in the numbers of CFU for both strains analysed. The differences between the two strains showed that Sinorhizobium meliloti survives better than Rhizobium trifolii to extreme temperatures. [ABSTRACT FROM AUTHOR]