جستجوی مقالات مرتبط با کلیدواژه « مراحل رشد » در نشریات گروه « زراعت »

Sugar beet, scientifically known as Beta vulgaris L, is allogamous, diploid, biennial plant of the spinach genus that is cultivated to produce storage roots. The growth period of sugar beet, depending on environmental conditions and genotype, varies from 5 to 9 months and is known as a late maturing plant. Therefore, estimating the yield reduction due to leaf fall plays an important role in farm management. In addition to the effects of stressors, some farmers may use sugar beet leaves to raise livestock during the growing season. In this case, too, the leaves are damaged. In the experiment of complete removal of leaves in three sugar beet cultivars, it was observed that complete removal of leaves in Antek and Vico cultivars led to reduced root yield and subsequently white sugar yield was significantly reduced, but In Sharif cultivar, leaf removal had no significant effect on root yield and sugar yield. They also reported that leaf removal increased the percentage of root sugar in Sharif cultivar. Effect of leaf removal time on quantitative and qualitative characteristics of autumn sugar beet cultivars in Gorgan region.

This experiment was carried out in factorial design during the 2019-2020 crop year in Varsen of Gorgan based on randomized complete block design with three replications. The first factor includes 6 autumn sugar beet cultivars including Monotana, Jerra-kws, Rosagold, Chimneh, Veles and Sharif and the second factor includes three levels, pruning in May (leaf development), pruning in June (reducing leaf development) and no pruning (control). Pruning was done using a sickle and the entire aerial part (petiole and leaves) was cut from a height of 5 cm above the crown. Seed bed preparation operations including plowing, retorting, leveling and farrowing were performed before planting. According to the planting plan, they were planted by hand on top of the ridges on November 2019. At the end of the growing season of each harvested plant, root yield and qualitative traits were calculated. The most common method of measuring sugar percentage by polarimetry method was calculated using saccharimeter, sodium and potassium by flame photometry method, harmful nitrogen by aqueous number method and other qualitative characteristics. The analyzed traits were analyzed using SAS software and the means were compared by LSD method at a statistical level of 5%.

Sugar beet cultivars showed significant differences in sugar content (grade), sodium, potassium, extractable sugar content, sugar and molasses extraction coefficient; However, no significant differences were observed between cultivars in terms of harmful nitrogen, alkalinity and root dry matter. Leaf pruning treatments except sodium and molasses were significant in other studied traits. The interaction between cultivars and pruning has also been significant in potassium and molasses traits. Significant differences were observed between the treatments by applying pruning treatment; So that the highest percentage of sugar (14.7%) was observed in the control treatment and the lowest percentage of sugar was observed in the June treatment (12%). The highest root yield was related to Chamineh cultivar with an average of 98 tons per hectare and the lowest root yield was related to Rosagold cultivar with an average of 80 tons per hectare. Due to the decrease in leaf production at the end of the sugar beet growing season, the amount of damage caused by root yield in leaf removal treatment in the final stages of growth (June pruning) is much less than the effect of leaf removal in the middle stage of growth.

Removal of sugar beet leaves in the final stages of growth had an effect on root quality properties such as sugar content, extractable sugar percentage and sugar extraction coefficient and root yield and reduced the mentioned traits. Root impurities also increased due to defoliation. Most yield losses were obtained when sugar beet leaves were removed or eliminated in the middle stages of growth (May pruning).

In the recent years, the study of genotypic variation in terms of efficiency of mineral nutrient has attracted the attention of researchers worldwide. Hence, to investigate the variation in the nitrogen (N), phosphorus (P) and potassium (K) use efficiency in 6 important crop and weed species (durum wheat, common barley, naked barley, triticale, wild oat and canary grass), a pot experiment was conducted as a factorial arrangement in a completely randomized design with three replications in Gorgan University of Agricultural Sciences during 2016-17 growing season. This experiment was carried out under unfertilized and fertilized at optimum rate conditions. Concentrations of elements and dry matter were measured in stem elongation, anthesis and physiological maturity. The results of variance analysis showed a significant effect of experimental factors on efficiency (dry matter to nutrient content ratio), nutrient efficiency ratio (dry matter in control to fertilized treatment ratio) and nutrient harvest index (nutrient content in grain to total dry matter ratio). There was no significant interaction between experimental factors for the traits studied in three stages. The results also showed a significant decrease in traits as a result of fertilizer application. According to the results, evaluation of nutrients efficiency in early stages of growth is not sufficient for comparison or screening of genotypes and should be done in more advanced stages, especially maturity. Also, considering the substantial variation among studied genotypes in terms of nutrient efficiency, more detailed studies on genotypic variation seems to be useful for identifying traits related to mineral nutrient efficiency.

Due to the lack of water in different regions of Iran, the introduction and use of indigenous species with valuable ornamental features such as mullein (Verbascum thapsus) is very important. V. thapsus is a perennial and evergreen herb belonging to the Scrophulariaceae family, which like other ornamental plants, can be affected by drought stress in the green space. Drought is an environmental stress that induces adverse effects on most stages of growth, structure and activities of plants. The response of plants to environmental stresses is different in morphological, cellular and molecular levels. Therefore, the present study was conducted to investigate the effect of drought stress on morphological, physiological and biochemical characteristics of V. thapsus during two stages of vegetative and reproductive growth.

In the present study, the reaction of V. thapsus to drought stress and its effect on vegetative and reproductive stages were investigated. The experiment was carried out as factorial in a completely randomized design with two factors as drought stress in 5 levels (control (0.3), 2, 5, 10 and 15 bar) and plant growth stages at two levels (vegetative and reproductive). For this purpose, shoot and root fresh weight, burn and wilt condition, leaf chlorophyll, activity of antioxidant enzymes and proline were measured.

The highest and lowest irrigation interval in both vegetative and reproductive stages was respectively found in 15 bar and control. The water volume used in vegetative stage was higher than reproductive stage. Shoot and root fresh weight in was reproductive stage was more than vegetative stage. The highest fresh weight of shoots was reported under drought stress in control and 2 bar and the lowest amount was observed in 15 bar, but the highest root fresh weight was observed in 5 bar. The highest percentage of leaf burns and wilt was observed in treatment of 15 bar × reproductive stage and its lowest in the treatments of control × vegetative stage and control × reproductive stage. Total chlorophyll in reproductive stage was more than vegetative stage. Also, the highest total chlorophyll was observed under drought stress in control and 2 bar and the lowest was found in 15 bar. The highest activity of superoxide dismutase and catalase was observed in 15 bar × reproductive stage and its lowest value was recorded in control × vegetative stage. Proline in reproductive stage was greater than the vegetative stage. The highest and lowest amount of peoline was observed in 15 bar and control, respectively.

The results of the research showed that the drought stress up to 5 bar did not cause significant changes in the plant, but increasing the intensity of drought stress from 5 bar to 10 bar induces the significant change of most traits in the plant. Therefore, with applying an appropriate plan, we can reduce the water use from 570 m3 (control) to 130 m3 (5 bar) during the vegetative stage and 500 m3 to 140 m3 for reproductive stage.

Studying phytochemical changes of fruits is very important for plant physiologists and pomologists. Date is an important horticultural fruit in Iran mainly produced in southern regions. Barhee is considered one of the most important date palm cultivars. The fruit of cv. Barhee can be harvested and consumed at different maturation stages including Khalal, Rutab and Tamar. In the present study, the biochemical alterations of date fruit cv. Barhee during development and ripening stages were studied.

The experiment was carried out in a randomized complete block design with three replications. Sampling was done at Date Palm Research Institute Collection Orchard located in Ahvaz. First, fruits were harvested in five different developmental stages including late Kimri, Khalal, mainly Khalal, mainly Rutab, fully Rutab and Tamar. The fruits were then transferred to Quality Analysis Lab of Department of Horticultural Science at Shahid Chamran University of Ahvaz. Selected uniform fruits were used for the analysis of different phytochemical compounds. Chlorophyll, carotenoid, starch, soluble sugars, phenolic compounds, flavonoids and antioxidant capacity were analysed using spectrophotometric methods. The type and concentration of sugars, organic acids, and phenolics were assessed using HPLC. Also, vitamin C content was determined by titration againt DCIP dye.

The results showed that soluble sugars increased significantly during ripening stages, and glucose and fructose were the main detected sugars for Barhee cultivar. The amount of sucrose was negligible. The acidity of the fruit increased at initial growth stages and then decreased gradually till Rutab stage. At the end of ripening process and at Tamar stage, the amount of organic acid content increased to 2.45 mg/g FW. Among the detected organic acids, acetic acid was dominant in Tamar stage, while in the earlier stages malic acid was considered the main organic acid. Other major investigated compounds, including flavonoids, chlorophylls, carotenoids, starch and vitamin C decreased during the development. Different compounds including p-cinamic, gintistic, gallic, chlorogenic, vanilic, caffeic, syringic and p-cumaric acids were detected by HPLC evaluation of phenolic acids. Among them, gallic acid was the dominant, and the trend was incremental during the development of fruit.

Comparing the current results with published data for other date cultivars shows that there are considerable differences in biochemical compounds among different cultivars. In this cultivar, the increasing trend of accumulation of soluble sugars, organic acids, phenolic compounds and antioxidant capacity during ripening stages from late Kimri to Rutab and Tamar stage makes the fruit an important source of essential nutrients.

This study was carried out to compare growth characteristics of three species of Alyssum minus, A. szwitsianum and A. desertorum over two years, 2017 and 2018, in a randomized complete block design with three replication at Isfahan Agricultural and Natural Resources Research and Education Center. Measured traits were yield characteristic including total dry weight, leaf, stem, root and seed dry weight; morphological characteristics including plant height, maximum and minimum plant diameter, plant cover and stem number; and phenolological characteristics including day to flowering, day to seeding and day to seed ripening. The highest biological and seed yield were achieved in A. minus, 1003 and 375 kg/ha respectively, while A. desertorum showed the lowest rates, 559 and 207 kg/ha respectively. Morphological traits analysis represented that A. minus had the highest rates of plant height, stem number, plant diameter and cover. A. minus and A. desertorum with 101 and 95 days to seed ripening were the longest and shortest lifelong species. The highest correlation rates between seed yield with other characteristics were including biological yield (0.90), plant height (0.79), stem number (0.76) and cover (0.75). On the whole, results of this study showed that A. minus showed the highest yield potential among the studied species.

Nitrogen is the most important limiting factor, after water deficit for biomass production in natural ecosystems. Efficient use of nitrogen fertilizer is important to economical dryland wheat production and to the quality of ground and surface waters. Researchers have been looking for ways to increase the efficiency of N fertilizer use. Soil and in-season plant tissue testing for nitrogen status are a time consuming and expensive process. Chlorophyll concentration in a leaf is closely correlated with leaf N concentration so the Soil Plant Analysis Development (SPAD) chlorophyll meter is one of the most commonly used diagnostic tools to measure crop nitrogen status. The SPAD chlorophyll meter is a simple, portable, diagnostic and nondestructive light weight device used to estimate leaf chlorophyll content. Chlorophyll meter techniques provide a substantial saving in time and resources and offer a new strategy for synchronizing nitrogen application with actual crop demand. The objective of this study was to establish and analyze the relationships between measurements from a SPAD instrument and the leaf pigments, as extracted at different stages. The study also seeks to evaluate the utility of a chlorophyll meter to inform nitrogen fertilization rates of wheat (Triticum aestivum L.) genotypes in dryland condition. This experiment was carried out in split split plot based on RCBD design with three replications. Treatment included: N application time (whole fertilization of N in fall, and its split fertilization as 2/3 in fall and 1/3 in spring), N rates (0, 30, 60 and 90 kg N ha-1) as urea and 7 genotypes (Azar2, Rasad, Ohadi, HN7/OROFEN//BGN8/3/SERI/4/.., SARA-BW-F6-06-85-86-29-1, TEVEE'S'//CROW/VEE'S' and DH-2049-3. A chlorophyll meter (SPAD-Hansatech Cl-01) was used to read leaf chlorophyll content (SPAD value) at tillering (GS22), shooting (29), stem elongation (GS32), flag leaf (GS39) and anthesis stages. Fresh plant leaf samples were collected from each plot for the estimation of chlorophyll a (Chla), chlorophyll b (Chlb), carotenoids (Ct), total chlorophyll (Chlt) and concentrations. The chlorophylls and carotenoids were determined by spectrophotometric analysis of chemically extracted pigments. To examine the relationship between pigments chlorophyll and SPAD values, 30 wheat leaves were sampled. Average Chla, Chlb, Chlt, carotenoids and SPAD values were computed, and linear regression analysis was performed by least-squares method with Excel. The results showed a strong positive and statistically significant (p<0.01) relationship between SPAD values and total chlorophyll (R2 = 0.93), chlorophyll a (R2 = 0.95), chlorophyll b (R2 = 0.78) and carotenoids content (R2 = 0.79). We demonstrated that the SPAD readings and plant photosynthetic pigment content per-leaf are profoundly affected by nitrogen rate and timing of application. Nitrogen split application increased significantly (p<0.01) the SPAD values (8.3%), Chla (11.1%), Chlb (10.9%), Chlc (27%), Chlt (15%), (exception of carotenoids) and seed protein content (8.5%). Nitrogen application could affect significantly (p <0.01) all chlorophyll indices in plant. The ideal conditions for the chlorophyll indices in the plant were obtained using 72 kg N ha-1. Nitrogen requirement for maximum and optimum economical dryland wheat production is about 20 and 10 kg ha-1 less than nitrogen requirement for creation the ideal conditions for chlorophyll status and its components in dryland wheat. Using chlorophyll meter, chlorophyll a (16.6 mg g-1), chlorophyll b (5.9 mg g-1), chlorophyll c (0.077 mg g-1), total chlorophyll (23.9 mg g-1) and chlorophyll a per Chlorophyll b ratio (2.78), chlorophyll index (9.4) and chlorophyll relative index (1.0) were determined in economical optimum N rate (NRD = 0). Genotype1 was most suitable and Azar2 was the most inappropriate condition in terms of chlorophyll index and total chlorophyll ratio per carotenoids (optimum range 40-70) in the plant as a stress resistance index. It can be concluded that, the actual chlorophyll content and its components can be estimated using chlorophyll meter (SPAD) in dryland wheat genotypes at different growth stages. Chlorophyll components and seed protein can be improved by nitrogen fertilizer application time and rates in dryland wheat.

This study aimed to investigate the relationship between morphophysiological and phenology traits with grain yield to determine the best indices of direct and indirect selection in the field of genetic improvement of aerobic rice grain yield in Khuzestan province with 12 aerobic rice genotypes. The traits such as include the grain yield as the dependent variable and total dry matter, panicle weight, stem weight, LAI, CGR, NAR, LAR, SLA, ALW, LWR, L/S, SWR, PWR, LAD and BMD as independent variables, which were analyzed by stepwise regression at different growth stages to determine their effect on grain yield. The results showed that on 25 days after planting traits of L/S, SLA, LAI and leaf weight, on 50 days after planting traits of NAR, L/S, SWR, stem weight and BMD, on 75 days after planting traits of NAR, SLA, stem and LAR, on 100 days after planting traits of CGR, stem, L/S, LAR and PWR and on 125 days after planting traits of CGR, NAR, SLA, L/S and leaf affected the grain yield. In order from the beginning to the end of the growth, traits of L/S, NAR, panicle weight, CGR and CGR had caused the greatest changes in the grain yield. According to the critical period of growth, CGR was the most effective trait on the grain yield because of allocation of more assimilates in the reproductive growth instead of vegetative growth during grain filling period, thus it can be an important objective in the breeding researches.

Drought is one of the major environmental conditions that adversely affects plant growth and crop yield. Drought is the most major restriction in maize production. The reduction in plant growth under drought stress conditions could be an outcome of altered hormonal balance and hence the exogenous application of growth regulators under stress conditions could be the possible means of reversing the effects of abiotic stress. Plant growth regulators such as auxin and cytokinin are known to be involved in the regulation of plant response to the adverse effects of stress conditions. Previous studies have shown that endogenous hormones are essential regulators for translocating and partitioning of photo-assimilates for grain filling in cereal crops (Yang, et al. 2003), and therefore could be involved in the regulation of grain weight and yield. This study was conducted to determine the effects of exogenous application of growth regulators on the current photosynthesis and remobilization of assimilates in maize cultivar KSC704 under drought stress conditions.
The experiment was carried out in three distinct environments at Seed and Plant Improvement Institute (SPII), Karaj, Iran, in 2013. The environments included non-drought stress (irrigation after soil moisture reached 75% of field capacity), drought stress at vegetative stage (irrigation after soil moisture reached 50% of field capacity from V4 to tasseling stage and irrigation after soil moisture reached 75% of field capacity from pollination to physiological maturity stage) and drought stress at reproductive stage (irrigation after soil moisture reached 75% of field capacity from V4 to tasseling stage and irrigation after soil moisture reached 50% of field capacity from pollination to physiological maturity stage). Cytokinin was applied at V5 –V6 and V8-V10 stages and auxin was sprayed at silk emergence stage and 15 days after that period. No usage of the growth regulators was served as control. The trial was laid out as a factorial scheme based on randomized complete block design with three replications. Auxin was used in the form of Indole-3-butyric acid and cytokinin was sprayed as N6-benzyladenin. Harvesting was done from 4.5 m2 at field maturity stage at 14 % grain moisture content and was used to estimate grain yield. Remobilization, efficiency of remobilization, contribution of remobilization, current photosynthesis, efficiency of current photosynthesis and contribution of current photosynthesis were measured by the equation of Uhart and Andrade (1995).
The effect of drought stress on current photosynthesis, efficiency of current photosynthesis, contribution of current photosynthesis and remobilization was significant (P Based on the results of this experiment, drought stress at vegetative stage (irrigation after decreasing soil moisture to 50% field capacity) can be effective in conserving irrigation water and increasing water use efficiency. Moreover, considering the fact that the higher rates of current photosynthesis and contribution of current photosynthesis to grain yield were achieved with cytokinin application at V8-V10 stage and spraying with auxin at silk emergence stage led to the increased rates of remobilization and contribution of remobilization to grain yield, the aforementioned growth periods were identified as the best application times for cytokinin and auxin, respectively.

In order to evaluate the quantitative and qualitative yield of peanut (Arachis hypogaea L.) in response to starter nitrogen rates two separate experiments were performed in 2013 and 2014 cropping season as randomized complete block design with three replications, in experimental field of Agricultural and Natural Resources Research and Education Center of Guilan Province, Rasht, Iran. Four rates of nitrogen including of zero, 100, 150 and 200 kg/ha comprised the experimental treatment. The results of this research showed that with increment of starter nitrogen application, duration of developmental stages in peanut enhanced. The greatest pod (3561 kg/ha) and seed yield (1740 kg/ha) of peanut, grain oil (49.86 percent) and nitrogen content (3.91 percent), oil yield (867 kg/ha) and protein yield (426.5 kg/ha) were obtained at 100 kg N/ha level. Application of 150 kg N/ha showed superiority for pod number per plant (21.30) and grain number per pod (1.39). Also, application of 200 kg N/ha caused to enhance plant height (73.35 cm) and grain phosphorus content (0.437 ppm) in peanut. In addition, there was negative and significant correlation between grain yield and some traits such as day number to initial flowering, day number to the end of flowering and maturity. The correlation coefficient between grain yield and oil (r= 0.99**) and protein yield (r= 0.89**) was positive and significant. In this experiment, oil and protein yield of peanut per unit area mostly related to grain yield. In general, results showed that the application of starter nitrogen up to 100 kg/ha enhanced pod and grain yield of peanut and oil and protein yield in Guilan province climatic condition.

An experiment to investigate wheat and wild barely phenology was conducted during 2008-2009 in the field of Plant Protection Research Institute in Varamin. Wild barely and wheat (Variety Kavier) were planted in the vicinity of each other in a randomized complete blocks design with four replications. Phenological stages based on international Zadoks scale and GDD based on growing degree days were calculated for each stage of growth. Results showed that wild barely finished its phenological stages faster than wheat. Thus, complete life cycle of wild barely required 1839/1 growing degree days and 204 days, while wheat needed 2143/1 growing degree days and 219 days. At wheat maturity seeds stage, wild barely seeds had completely fallen except for the final seed clusters. Wild barely seed dormancy period was about 45 days. Comparative study of phonological stages of wild barely and wheat showed that the plants grew together of early stages, of growth up to early tillering, from then to the end of tillering, wild barely surpassed wheat. However, in the stem elongation stage wheat surpassed wild barely. However wild barely started inflorescenc emergence sooner than wheat. Our results suppots the idea that success of wild barely to infest wheat fields is due to rapidly reaching full maturity and short seed dormancy period.

Evapotranspiration is one of the most important elements of hydrological cycle which is required for water resource management and design of irrigation systems. Crop evapotranspiration (ETc) can be measured by the Lysimeter using water balance equation. It also can be estimated by multiplying reference evapotranspiration (ETo) and crop coefficient (Kc). Considering the importance of this parameter, numerous studies have been performed to determine the Kc of major crops in each region. Lentil is one of the legumes which is cultivated mainly in Lorestan province. Although this crop is the second in terms of the area under cultivation among the legumes in the country, the water requirement and crop coefficients of this crop is not determined in Lorestan province yet. The main purpose of the current study is to determinate lentil water requirement and its Kc in Khorram Abad.
A lysimetric experiment was conducted during the lentil growth season in 2013 at the research farm of agricultural faculty, Khorram Abad, Lorestan University. The farm is located in a cold semi-arid climate. Physical and chemical properties of the soil in the lysimeters were determined in the laboratory. The average of soil moisture content in the lysimeter at the field capacity and permanent wilting point was determined as 34.4 and 24.8 volumetric percentage respectively. In this study, lentil (Gachsaran cultivar) and grass were cultivated each on four micro drainable lysimeter with the diameter of 48 cm and height of 80 cm. Maximum allowable depletion (MAD) of soil moisture was considered as 30% to ensure that crops are not faced with water stress. Length of the crop growth stages (initial, development, mid-season and late-season) was determined by daily observation of the field and measuring crop canopy. Lentil and grass evapotranspiration was determined using water balance method. The evapotranspiration from grass was considered as reference evapotranspiration (ETo). The measured values of ETo and lentil evapotranspiration was compared with the calculated values by CROPWAT, REF-ET and AGWAT (Basis of national document of water) packages. Crop coefficient (Kc) was calculated as the ratio of lentil evapotranspiration over ETo. Average of Kc for each stage was also calculated and compared with literature.
The average of reference crop evapotranspiration (ETo) was increasing thorough the growth period of lentil from 3.7 to 8.6 mm.day-1. This was due to increasing of sunshine hours and air temperature during that period. Total amount of lentil and grass evapotranspiration during the growing period of lentil was determined as 476 and 568 mm respectively. Total amount of calculated ETo in this period by CROPWAT, REF-ET and AGWAT packages was 551, 566 and 340 mm respectively. Results indicated that calculated values of ETo by CROPWAT and REF-ET is almost equals to measured ETo. However, AGWAT also uses Penman-Monteith equation but its results were far from the measured values of ETo because of differences in weather data. Results also indicated that lentil evapotranspiration was low at the initial stage, increased during the development stage and decreased during the late season. The maximum crop evapotranspiration of 88.46 mm per decade was measured at the period of 16-25 May 2013. Measured lentil evapotranspiration in the current study was higher than values calculated by AGWAT software package for this region. Lengths of initial, development, mid-season and late-season stages were determined as 19, 20, 33 and 24 days respectively. The average of lentil crop coefficient for initial, development, mid-season and late-season stages was calculated as 0.45, 0.89, 1.19 and 0.56 respectively. Calculated Kc values in this study were compared with the values of Kc in FAO 56 report and AGWAT. Calculated Kc at initial and mid stages (0.45 and 1.19 respectively) were close to values reported in FAO 56 (0.4 and 1.1 respectively) but far from AGWAT (0.15 and 1.05 respectively). In general, calculated crop coefficients in the current study were higher than the values presented in FAO 56 and AGWAT package software. Measured values of lentil evapotranspiration were higher than values reported in AGWAT. The reason was underestimation of ETO by AGWAT and lower values of Kc for lentil.
As there was no measurement of lentil evapotranspiration and crop coefficient, the results of current study can be used as a base for further studies about this issue in the region. Comparison of measured values of ETo and lentil crop evapotranspiration with the values calculated by AGWAT package indicated the under estimation of both parameters by AGWAT. However, it is recommended to do more studies on this subject but the results of current study can be used to determine lentil evapotranspiration instead of values reported in AGWAT and national documents of water for Lorestan province.

In order to evaluate the effects of salt stress in different growth stages on morpho physiological traits in rice, a greenhouse experiments was conducted in three replications with using two rice cultivars, including Daylam and PSBRC88 as main plats, as well as three salinity levels including 0, 6 and 12 dS/m at vegetative growth, stem elongation and flowering as sub-plots in a split plot factorial based on RCBD. Salinity treatments were imposed for 20 days in nutrition solution at each stage. Results showed that total and leaf area as well as their dry weight, decreased with increasing salinity at different growth stages. K+ concentration with increasing salinity levels decreased while that of Na+ increased. The SPAD value, RWC, stomatal conductance and photosynthetic rate also declined. Reduction at flowering stage was more than vegetative growth and stem elongation stages. The maximum reduction in dry matter in any growth stage of growth, was observed at 12 dS m salinity level. Saline water with EC 12 dS/m, at the flowering stage reduced leaf area, total dry weight, photosynthetic rate and stomatal conductance by as much as 12, 25, 48 and 55 percent.

In order to investigate the seed vigor of corn hybrid 704 after maternal plant foliar application with methanol and some micro-macronutrients an experiment was conducted in factorial form based on RCBD with three replications during growing seasons of 2010-2011. Treatments were four growth stages (the 8-10 leaves، the tasseling، the seed-filling، all the stages)، seven levels of foliar application (Methanol، Zn، B، Mg، N، Mn، a mixture of all combinations) and control. The analysis of the data showed a significant effect of the combination type of foliar application in different stages on the germination percent، mean daily germination، germination speed، seedling vigor index، radical length، plumule length and seedling dry weight. The detailed results of the study showed that foliar application with N، Mg، Zn، Mn and B in grain-filling stage، foliar application with N، Mg and Mn in tasseling and foliar application with N، Mg and B in all stages had the highest germination percent (100%) and mean daily germination (14. 29%). Also، Mg-foliar application in grain-filling and all stages، B-foliar application in grain-filling stage had the highest germination seed (12. 33). In addition، Mg-foliar application in grain-filling stage had the vigor index، radical length، plumule length and seedling dry weight.

To determine salinity tolerance of wheat (Triticum aestivum L.) at various growth stages، a controlled experiment (lysimeter conditions) was conducted at the National Salinity Research Center. Experimental design consisted of six treatments replicated three times in a randomized complete block design. Treatments were application of salinity at establishment stage، tillering، stem elongation، spike emergence، during grain filling period till final growing season and without imposing salinity (control). Wheat plants were grown in eighteen boxes (0. 5×0. 4 m and 0. 5 m depth) contained washed sand. Plants were irrigated 2-4 times daily using nutrient solution. The results showed that from emergence to tillering and from emergence to stem elongation phases were two sensitive stages of wheat growth to salinity stress and spike length and plant height were reduced significantly. Biological yield was considerably reduced by imposing salinity at establishment stage through growing season. Delay in application of salinity was associated with lower reduction in biological yield. Salinity reduced grain yield more severely when salinity stress was imposed at earlier stage of growth. Based on the results reduction in biological yield and the number of plants per unit area were the main contributing factors in grain yield reduction under salinity stress conditions.

In order to evaluate the effect of salinity on some traits in different cultivars of barley at different growth stages, this experiment was conducted in vitro and field culture environment in Sadough research farm, dependent to Salinity Research National Center in cropping year 2012-2013. The germination of Afzal, Nosrat, Reihan, 4shoori and Rodasht cultivars in response to different levels of salinity 5, 10, 15, 20 and 25 dS.m-1 and distilled water as control was studied in vitro culture as factorial based on completely randomized design with three replications. The results showed that the greatest germination reduction was at salinity level of 20 dS.m-1. Also, among the tested cultivars, cultivars of Afzaland and 4Shoori with 58.6 percentage and 58.53 percentage presented the percent of germination comparing to the other cultivars, respectively. Experiment in the culture of field was conducted as split plot based on randomized complete blocks design with four replications. Different salinity were applied at main plots and five under-investigating cultivars in subplots at three levels including the amounts of 4, 8 and 14 dS.m-1. Effect of salinity treatment on all understudying traits (except spike length) was significant at one percentage probability level and five percentage probability level on spike length. Although most of the traits decreased due to salinity tension, but applying salinity increased sodium and potassium of grain. Grain yield decreased and the cultivars showed significant difference, by increasing salinity tension. The salinity interaction in cultivar showed the lowest yield in 14 dS.m-1 salinity Nosrat, Reihan, 4shoori and Rodasht cultivars and Afzal cultivar was superior in the salinity than other cultivars.

This study was conducted to determine the yield response factor (Ky) of wheat with respect to deficit irrigation at different growth stages. The experiment was conducted in Shahrekord in three crop growing seasons using randomized complete blocks design with 3 replications. Treatments consisted of five levels of deficit irrigation: E0 (full irrigation), E1 (85%), E2 (70%) and E3 (55%) of potential evapotranspiration of wheat and E4 (no irrigation), and were assigned to six growth stages: T1 (establishment), T2 (tillering), T3 (head development), T4 (flowering), T5 (milk ripeness) and T6 (maturity harvest). Potential evapotranspiration was measured using a lysimeter, which was in conditions (soil texture and structure and plant growth) similar to the field. After harvesting the plants, grain yield was measured and wheat yield response factor was calculated. Results of combined analysis of variance showed that grain yield was significantly affected by deficit irrigation at establishment, tillering, head development, flowering and milk ripeness stages. The highest and the lowest grain yields (6354 and 2203 kg/ha, respectively) were obtained in E0 and E4 treatments, respectively. Potential evapotranspiration of wheat was 641 mm in this area. Yield response factors (ky) were 0.55-0.76 in T1 growth stage, 0.58-0.97 in T2, 0.70-1.43 in T3, 0.75-1.45 in T4, 0.68-0.95 in T5 and 0.52-0.58 in T6. In general, in all plant growth stages, actual and relative yields decrease as relative evapotranspiration decreases.

Drought stress is the most important limiting factor in crop plants including maize (Zea mays L.), which is the third important world crop after wheat and rice. Water deficiency at different growth stages affects maize yield differently. To examine the response of four maize hybrids to drought stress at different growth stages, a field experiment was carried out as a split plot based on completely randomized block design at Research Farm of College of Agriculture, Shiraz University, during 2009 and 2010 growing seasons. The main plots composed of four drought stress levels including optimum irrigation, withholding irrigation at vegetative growth stage (8-leaf to flowering), flowering and kernel filling. Four maize hybrids including Zola, BC666, Maxima and SC704 were allocated into sub-plots. Data analysis showed that the effect of year was not significant on measured characters; thus, the data of both years were combined. Drought stress affected all measured characters except number of kernels per ear. The most significant effect of drought stress at vegetative growth phase was on reduction of plant height (10.2%). Drought stress at flowering reduced ear length (12.6%), kernel per ear (17.8%), yield (29.1%) and harvest index (20.4%). The 1000-kernel weight was significantly reduced (10.3%) when drought stress occurred at kernel filling stage. SC704 hybrid had the highest height (281.07 cm), kernel per ear (710.62), ear length (19.45 cm), 1000-kernel weight (316.49 gr), biological yield (25368 kg/ha) and kernel weight (11291 kg/ha). The highest harvest index (46.99%) was achieved in Maxima hybrid. It appears that flowering stage was the most sensitive stage to drought. Although drought stress at all growth stages reduced maize yield, but in dry areas, it might be possible to accept a small reduction in maize yield and save an irrigation in favor of other crops, simultaneously grown with maize. According to the results of this 2-year experiment, Maxima hybrid appeared to be suitable for drought-prone areas, while SC704 is better for normal conditions.

In order to investigate respond of yield and yield component of three maize hybrids on seven plant densities, an experiment was conducted during 2007-2006 growing season in Mashhed, Iran. Three maize hybrids including long season maize (704), medium season maize (504) and short season maize (260) and five growth stages includingV5, V7, Vt, R3 and R5 were compared in a strip plots design with three replications. There was significant difference among number of ear per plant, number of seed row on each ear, number of seed per each plant, seed weight per each plant, 100 seed weights weight of dry cob per each ear, yield and yield biology between thinned plants in the R3 و R5 stages and V5، V7 stages. However, yield and yield components were closed to optimum density per hybrids in thinned plants at the V5، V7 stages but there was significant difference among yield and yield components in thinned plants at the R3 و R5 stages

In order to study the effects of foliar application of Zn and K on yield and some physiological traits of spring safflower (Carthamus tinctorius L.), cv. Esfahan 14, under drought stress, a pot experiment was conducted in research greenhouse of Yasouj University. Experiment was a factorial based on completely randomized design with three replications. Factors consisted of drought stress (S1- without stress, S2- stress at vegetative stage, S3- stress at reproductive stage and S4- stress at seed filling stage) and foliar application of nutrients (F1- without foliar application, F2- foliar application of water, F3- foliar application of zinc sulfate and F4- foliar application of potassium sulfate). Results showed that in drought stress at vegetative phase, foliar application of potassium has maximum chlorophyll a (25.7%), proline (87.8%) and total soluble sugars (26.9%) compared to without foliar application. Foliar application, compared to without foliar application, increased chlorophyll a (26%), chlorophyll a+b (32%), proline (51%) and total soluble sugars (26.9%) at S3 stress. However, in stress at seed filling stage, total soluble sugars increased (41.4%) by foliar application only. Grain yield increased by foliar application of zinc and potassium at all stress treatments except the reproductive stage stress. Finally, foliar application of zinc and potassium increased the concentration of osmolytes, such as total soluble sugars and proline and led to improved osmotic adjustment and plant tolerant to drought stress.Keywords: Chlorophyll; Growth stages; Proline; Total soluble sugars