To evaluate the effect of nitrogen and water withholding in vegetative growth stage of corn on efficacy of nicosulfuron and 2,4-D+ MCPA an experiment was conducted as a factorial arrangement in a randomized complete block design with three replications at Tarbiat Modares University in 2017. The first factor contained four treatments including application of nicosulfuron, 2,4-D+ MCPA, weed free and weed infested as control. The second factor consisted of normal irrigation and water withholding from 4 to 8 leaf stage. Third factor contained either urea application or no fertilizer application. Normal irrigation and nitrogen fertilizer application significantly increased nicosulfuron and 2,4-D+ MCPA efficacy in weed control and total weed dry weight decreased to 341 and 361 g.m-2 respectively compared 1370 g.m-2 as weed infested. Nicosulfuron and 2,4-D+ MCPA reduced weed total dry weight significantly under irrigation withholding. Grain yield increased with application of nitrogen and nicosulfuron. Grain yield was higher with application of 2,4-D+ MCPA than nicosulfuron without nitrogen application under irrigation withholding. Application of nicosulfuron with nitrogen application provided satisfactory weed control and increased grain yield.

Acer velutinum Boiss. (Persian or velvet maple) is one of the industrial and important species of Hyrcanian (Caspian) forests with wide distribution. This species is rarely seen in the forests of other parts of the world and has only been reported from the forests of the Caucasus. Therefore the information about this species is very limited. This research aims to investigate  the response of A. velutinum seedlings to drought stress as one of the consequences of climate change. Seedlings of velvet maple were analyzed in terms of height, basal diameter, leaf area (LA), specific leaf area (SLA), biomass, photosynthesis pigments, relative water content RWC), free proline, malondialdehyde (MDA), superoxide dismutase(SOD), and peroxidase(POD) activities to drought stress. One year old of Potted plants were exposed to four water supply regimes (100, 75, 50, and 25% field capacity (FC); performed as a control, mild, moderate, and severe water stress. The results showed that drought reduced all aspects of growth in the velvet maple. It negatively affected on growth and reduced plant height, stem diameter, biomass, and leaf area, but SLA significantly increased under moderate treatment. Drought stress reduced chlorophyll content, however, no significant difference was found for carotenoids. RWC reduced significantly just under severe drought stress. Proline and MDA content increased significantly when plants were exposed to moderate and severe drought stress. Drought stress induced POD and SOD activity under drought treatments, although the highest activities were measured under mild and moderate treatments. Our data demonstrate that A. velutinum seedlings have relative drought resistance. They used drought avoidance and tolerance mechanisms through changes in morpho-physiological characteristics. The results of this research briefly showed the mechanisms of drought tolerance in A. velutinum and will provide essential information for more research in the future.

Iran, due to its geographical location, has low rainfall and is considered a dry land. As a result, different regions of the country grapple with drought. The presence of water management systems, such as aqueducts and reservoirs, in most parts of the country, along with a variety of methods for conserving water for irrigation, may contribute to this claim. Considering that drought is an inherent phenomenon in Iran's climate, people have invented and used numerous methods to combat it and store water. The aim of this study is to monitor and evaluate drought in Iran. In order to realize this goal, precipitation data from synoptic, rain gauge, and climatology stations were extracted over a 51-year period, from 1970 to 2020. The results obtained from examining drought occurrences in five ten-year periods reveal that, with the exception of the third decade (1991 to 2000), drought has prevailed in the majority of Iran's regions compared to other decades. On the other hand, in the recent decades leading to 2020, the intensity of drought occurrences, especially in the Middle Zagros, has intensified, which has consistently been among the regions with the highest rainfall in Iran after the Caspian region. This situation can cause concern in Iran, a country where its agricultural production hub is established along the Zagros mountain range. Moreover, the fluctuating behavior of Iran's droughts, with return periods of 2 to 5 years, has complicated the management strategies for these types of hazards. These conditions appear to have created numerous issues in many areas of Iran, particularly in the agricultural sector of the western provinces, due to the lack of conformity with these types of occurrences.

In order to identify the correlations and relationships between different traits in the bread wheat, 30 genotypes were investigated as sub-factors under the split plot experiment in the completely randomized design in greenhouse and the randomized complete block design in the field with three replications under the normal irrigation and post-anthesis water stress conditions. The results of the canonical correlation analysis showed that at both normal and moisture stress levels, there was a significant correlation between the pair of canonical variables obtained from the phenological traits and the yield components. Under the normal conditions in the greenhouse, to increase the spike density and length, the number of days to 50% flowering can be considered as a suitable selection criterion. According to the results of canonical correlation analysis, under the stressed conditions in greenhouse, to increase the spike length, the number of days to the heading, maturity and 50% of flowering were among the important and effective factors. Under the optimum irrigation conditions in the field, the number of days to maturity was considered as one of the factors influencing the seed weight per spike. The results of canonical correlation analysis under the field stress conditions showed that to increase the 1000-seed weight, the number of days to maturity can be considered an appropriate selection criterion.

To study the effects of end season drought stress on yield, yield components and drought stress indices in barley, a split plot experiment arranged in randomized complete block design with three replications was conducted at the Agricultural Research Center of Birjand in 2008-2009 crop years. Drought stress, in 2 levels, consists of control (complete irrigation) and stopping irrigation at the 50% of heading stage, and 20 promising genotypes of barley were the treatments of the experiment. Results revealed that stopping irrigation lead to declining of 14.64 and 8.12 percent of seed and forage yields against control condition, respectively. Using stress susceptibility index (SSI) indicated that genotypes 2, 3, 7, 9, 10 and 15; using STI and GMP indices, genotypes 5, 8, 18 and 20 using MP, genotypes 8, 18 and 20, and TOL, genotypes 2, 3, 7, 9, and 10, were the most drought tolerant genotypes. Correlation between seed yield and stress evaluation indices showed that MP, GMP and STI are the best indices to be used in selection and introducing drought tolerant genotypes of barley. Considering all indices, and given that the best genotypes are those with high yield under normal condition and minimum yield reduction under drought stress, No. 18 and 20 could be introduced as the most tolerant barley genotypes to drought.

In order to identify drought tolerance barley genotypes, screen quantitative indices drought tolerance and appointment best indices, one experiment carried out with 20 barley genotype. This experiment excuted in RCBD with three replications under full irrigation and drought stress conditions during 2009-2010, cropping season in broujerd agricultural research station. In order to evaluation of barley genotype for drought stress, stress susceptibility index (SSI), stress tolerance index (STI), geometric mean productively (GMP), tolerance index (TOL), mean productivity and harmonic mean (HM), data were collected. The result indicated significant different among all genotypes with respect to all quantitative indices and yield performance in both environments. This show the possibility of selection for drought tolerance among genotypes, and involvement of superior ones inbreeding programs. The result of experiment showed that No.7 (MB-79-4) genotype in the irrigation condition and NO.14 (MB-82-4) in dry condition has the highest grain yield. Highest HM, GMP, MP and STI were obtained in the No. 11 and 14 (CB-83-15 and MB-82-4) genotypes. Evaluation of genotypes for stress TOL and SSI index showed that No. 6 (CB-83-17) genotype has high index. Correlation analysis between yield and all indices revealed that MP, GMP, HM and STI are all indices for screening of drought tolerance genotypes. Accordingly, genotypes No. 7, 11, 14 and 19 (MB-79-4, CB-83-15, MB-82-4 and MB-79-15) were selected as drought tolerance genotypes. Biplot multivariate technique located the genotype No. 7, 11, 14 and 19 (MB-79-4, CB-83-15, MB-82-4 and CB-84-10) near the vectors related to drought resistance indices.

Introduction and Objective: In semi-arid areas such as a large part of Iran, due to rainfall unfavorable distribution and temperature sudden increase in time of grain filling, soil moisture decrease is considered as one of the most important factors in the reduction of wheat growth and development, Therefore, by evaluating the effects of drought stress on the studied cultivars, it is possible to identify the most favorable cultivars and use them for future breeding purposes. Therefore, the purpose of this research was to identify drought tolerant cultivars and their characteristics with the help of drought tolerant indices that cause higher yield in dry climatic conditions. Material and Methods: The present experiment was designed and implemented in the educational-research farm of Payame Noor University, Asadabad center, in the form of a randomized complete block design with three replications in two conditions of moisture treatment in the crop year 2015-2016. Moisture treatment was carried out in the conditions of drought stress in the form of interruption of irrigation after flowering and in conditions without drought stress. Were used in this research number 14 cultivar of old and new varieties of bread wheat. Drought tolerance indices were used in this research. Results: The results of mean comparing of this experiment showed that the highest mean yield in the conditions without drought stress and drought stress condition was cultivar No. 10 and 2, respectively. Cultivar No, 10, 2 and 6 had the highest Stress Tolerance Index, Mean Productivity, Geometric Mean Productivity, Harmonic Index, Abiotic-Stress Tolerance Index, Modified Stress Tolerance index in without Drought Stress, Modified Stress Tolerance Index in Drought Stress and Stress Tolerance Score Indices. The results of the correlation analysis between the indices and the mean yield in the non-drought stress conditions and drought stress condition showed that the most suitable indices for screening cultivars in two environmental conditions were STI, ATI, K1STI, K2STI, STS, MP, HAM and GMP. Also, Principal Components Analysis showed that 69.3% of the changes of the examined variables in the of non-drought stress conditions and drought stress conditions can be explained by the first component and 99.4% of the said changes can be explained by the first and second components. Conclusion: In this study, STI, ATI, K1STI, K2STI, STS, MP, HAM and GMP indexes were found to be favorable. Therefore, these indices were able to identify drought tolerant cultivars with optimal performance in both environmental conditions under investigation (non-drought stress conditions and drought stress conditions). The cultivars that were able to be selected in both environmental conditions by the mentioned indices included cultivars No. 10, 2 and 6, respectively.