New metabolic profiling technologies provide data on a wider range of metabolites than traditional targeted approaches. Metabolomic technologies currently facilitate acquisition of multivariate metabolic data using diverse, mostly hyphenated, chromatographic detection systems, such as GC-MS or liquid chromatography coupled to mass spectrometry, Fourier-transformed infrared spectroscopy or NMR-based methods. Analysis of the resulting data can be performed through a combination of non-supervised and supervised statistical methods, such as independent component analysis and analysis of variance, respectively. These methods reduce the complex data sets to information, which is relevant for the discovery of metabolic markers or for hypothesis-driven, pathway-based analysis. Plant responses to salinity involve changes in the activity of genes and proteins, which invariably lead to changes in plant metabolism. Here, we highlight a selection of recent publications in the salt stress field, and use gas chromatography time-of-flight mass spectrometry profiles of polar fractions from the plant models, Arabidopsis thaliana, Lotus japonicus and Oryza sativa to demonstrate the power of metabolite profiling. We present evidence for conserved and divergent metabolic responses among these three species and conclude that a change in the balance between amino acids and organic acids may be a conserved metabolic response of plants to salt stress.

SummaryTo study the effects of high temperature on the meiosis of pollen mother cells (PMCs) and to determine their relationship with grain set, two in situ experiments were conducted between 2010 and 2012 on four wheat cultivars, Kauz, Montana, M6 and Chamran, under normal (normal cultivation) and terminal heat stress (late cultivation) conditions. Due to the delay in cultivation for the cultivars under stress conditions, their flowering stage faced heat stress at the end of the growing season, and therefore, a significant (p ≤ 0.05) increase was observed in meiotic abnormalities. Cytogenetic studies discovered that the meiosis in PMCs and the pollen development are strongly influenced by heat. Based on the results, abnormalities such as precocious chromosome migration to the poles, laggard chromosomes, micronuclei, absence of metaphase plate, pyknosis, abnormal cytokines, cytomixis and abnormal tetrad were observed in different cultivars. The sensitive cultivars, M6 and Montana, had the greatest percentages of meiotic abnormalities. The meiotic abnormalities showed a significant negative correlation with the number of kernels per spike under terminal heat stress conditions (r = 0.54, n =16, p ≤ 0.01). In other words, due to increasing meiosis abnormalities under terminal heat stress, the grain set was greatly reduced, especially in the susceptible cultivars. The result of this experiment showed that studying the meiosis in PMCs can be suggested as one of the research necessary to improve commercial heat-tolerant cultivars, and to some extent, as a method for screening tolerant lines in breeding programs.

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Evaluating physiological traits involved in the response of plants to drought stress could lead us to improve drought tolerance in crops. In this regard, the current project was conducted under a line-source sprinkler irrigation system. Eight commercial bread wheat cultivars {Triticum aestivum L.) were evaluated at four water levels (WL) based on evapotraspiration (ET; WL1, supplying 100% of ET water to WL4, supplying 25% of ET water). Among the cultivars Chamran and Kavir had the highest grain yield at WL4 (4450.7 and 4317.3 kg ha-\ respectively) and noticeable grain yield stability in different water levels. Water use efficiency (WUE) ranged between 5.092 and 7.296 kg ha"m m"^and significantly varied among cultivars in different WLs. Under WL4, Niknejad and Kavir had the highest and Shiraz had the lowest value for WUE. Regression analysis confirmed that the relationship between dry matter and ET follows a linear function. Furthermore, evapotranspiration efficiency (ETE) as calculated by dividing the total biomass by ET was a reliable physiological indicator for cultivar evaluation with regard to water deficit tolerance in different growing stages. Based on this indicator, it was discovered that Mahdavie has the highest ETE from planting to stem elongation, Niknejad from planting to flowering, Pishtaz from planting to dough development and ripening, and Kavir has tolerance against water deficit throughout the growing season.

Improving grain performance under water-limited conditions essentially depends on the knowledge of water-yield relationships. Th e current project was set up to make a fi eld evaluation of relations among grain yield, water use effi ciency (WUE), and its components, i.e., transpiration effi ciency (TE), uptake effi ciency (UE), and harvest index (HI) in bread wheat (Triticum aestivum L.) genotypes. Eight bread wheat genotypes and four water levels (WLs) based on evapotranspiration (ET; WL1, supplying 100% of ET water, to WL4, supplying 25% of ET water) were included in 3-yr experiments. Th e experiments were conducted under a line-source sprinkler irrigation system. Th e results of regression analysis revealed that grain yield, WUE, HI, TE, and UE showed linear regression lines against ET. Th ese regression lines ascended for grain yield, WUE, HI, and UE but descended for TE. Th e best-fi t model between WUE and its components was linear and showed an ascending trend for HI and UE but descending trend for TE. Th e results of this experiment showed that an increase in TE could improve the WUE in wheat genotypes considering that HI is high. Th at is, applying selection for both TE and HI under water-stress conditions might give the best results to improve WUE in breeding programs.

Investigation of aberrations caused by gamma radiation in mitosis and meiosis might be fundamental to elucidate the interaction between radiations and biological systems. To identify the effects of the various doses of gamma radiation (25, 35, 45, 55 Gy) on mitotic and meiotic traits and agronomical features, a field experiment and microscopy assays were conducted on M2 generation of Vicia faba cv. Saraziri. Various types of mitotic and meiotic anomalies including laggard chromosomes, precocious movement of chromosome, anaphase and telophase bridge, chromosome fragments, chromosome stickiness, micronuclei, disturbed anaphase, vagrant chromosomes, the trinucleate status in telophase and tripolar anaphase were observed in root meristem cells and pollen mother cells (PMCs). The meiosis of PMCs showed less sensitivity towards gamma radiation than mitosis of root meristem cells. Among different stages of mitosis and meiosis, the most anomalies in terms of frequency were attributed to anaphase in mitosis and telophase II in meiosis. The recorded data of different anomalies confirmed that the micronuclei in telophase of mitosis and meiosis had the most frequencies in all gamma ray doses. The effects of different doses of gamma rays on agronomic traits including the number of pods per plant, number of seeds per pod, number of seeds per plant, and seed yield per plant were significant and the values decreased as the irradiation dose increased. Moreover, increasing irradiation doses caused a delay in flowering, pod setting, and pod ripening period. The highly negative correlations between mitosis and meiosis anomalies and agronomical traits were reported in this research.

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