مجله تنشهای محیطی در علوم زراعی
سال یکم شماره 1 (زمستان 1387)

In order to evaluate effects of drought stress on yield and yield components of two wheat cultivars under field condition, two similar experiments were conducted in 2004 in Field Research Stations of Islamic Azad Universities of Karaj and Torbat-e-Jam Unites. The study was arranged as factorial experiments based on a randomized complete block design with four replications. The first factor was consisted of nine different irrigation regimes including control (T1), irrigating when 60 and 80 percent of soil moisture was depleted at stem elongation to ripening stage (T2 and T3, respectively), at the start of flowering to ripening (T5 and T7, respectively), at flowering stage (T4 and T6, respectively), and irrigation termination at flowering and grain filling stages to ripening stage (T8 and T9, respectively). The second factor was included two wheat cultivars, Chamran and Marvdasht. Results showed a significant difference between different treatments of drought stress and control regarding yield and yield components. Irrigation termination from flowering onward led to the lowest grain yield, with 64 percent reduction compared to control. The lowest yield reduction equal to 19 percent beside control was obtained with irrigating at 60 percent soil moisture depletion from stem elongation up to end of growth period. According to these results, the most sensitive growth stages of wheat to drought stress were flowering and grain filling stages. Marvdasht despite its higher yield under sufficient moisture condition, and even under water-deficit through growth period, suffered more damage than Chamran from terminal irrigation termination. Under optimum condition of humidity, grains per spike and length of peduncle showed higher correlation with grain yield, respectively. When irrigation was withheld from flowering to ripening stage, weight of 1000 kernels showed a positive and significant correlation with yield, indicating that impact of water stress in this stage on yield was mediated by reduction of kernel weight.

The main factor for managing and scheduling irrigation in dry zone, recognition of plant response to dryness stress. Most irrigation water in Birjand area have saline solution, therefore, salinity stress should be considered at the stimulatingly. Hens, this study was conducted in order to obtain the optimum depth of irrigation scheduling, considering dryness and salinity individually and stimulatingly during 2006 agriculture year, in agricultural research station at Birjand university. The experiment had three replications according to a randomized complete block design with split plot layout (factorial form), which considered three levels of water salinity (1.4, 4.5, 9.6 dS m-1) as main plot and four levels of irrigation water (50, 75, 100, 125 % of plant water requirement) and two wheat varieties as sub plot. The irrigation depth for different salinity levels and the two cultivars was determined. The crop yield under different conditions was determined using production functions, than the optimum irrigation area net income for available water (10000 m3) was assessed. The results showed that by increasing salinity stress, the irrigating depth of both wheat cultivars were a little decreased that was not reflected in real condition. The reason for reduction in irrigation depth is related to water price for different salinity levels that was accounted as constant, where, the crop yield during various salinity stress severities would be different. Also, under dryness stress, and increase salinity stress conditions for both wheat cultivars, the irrigation depth, were increased. The reason for this increase in irrigation depth was reduction in yield high levels of salinity stress that was resulted from changing of production function to the irrigating depth. Therefore, at high salinity stress levels, deficit irrigation would malfunction and would not be economically feasible. For all available water levels, the irrigation depth was higher for Ghods cultivar then Roshan cultivar. This factor was responsible for obtaining optimum irrigation area for Ghods cultivar compared to Roshan cultivar in various salinity levels and resulted that the net income of Roshan cultivar was more than Ghods cultivar in all levels. Overall, where the available water quantity is considered and quality is not favorable (saline) using Roshan cultivar is highly more economical in Birjand region.

Dry land salinity is one of the major problems affecting agricultural products. The main consequences of plant exposure to salt stress are water deficit and ion excess, which lead to several morphological and physiological changes. In order to evaluate the effect of Salinity on some physiological characteristics of 8 spring rapeseed cultivars, an experiment was conducted in the greenhouse at Yasouj University as a factorial in a complete randomized design with three replications. The first factor includes four salinity levels (1.92 (as control), 9.87, 19.6 and 21.94 dSm-1 (NaCl and CaCl2 with ratio 20 to 1 in Hoagland solution)) and the second one includes eight cultivars (PP-308-8, PP-401-16, Hyola330, Hyola60, Hyola401, Rgsoo, Oftion500 and PP-401-15E). Leaf K+, Ca2+, Na+ and Mg2+ concentration and K+ to Na+ ratio, biological yield, grain yield and oil percentage were measured. Results showed that with increasing salinity levels, leaf K+ concentration, K+ to Na+ ratio, biological yield, grain yield and percent oil significantly decreased, but leaf Na+ and Mg2+ increased. High grain yield cultivars (Hyola 60 and Hyola 330) had significant lower concentration of Na+, Ca2+ and Mg2+ and higher leaf K+ concentration and K+/Na+ ratio. In summary, Hyola 60 and Hyola 330 cultivars that had higher yield than the other cultivars were the most tolerant and PP-401-15E and Oftion500 cultivars were as the most sensitive cultivars to salinity respectively.

Germination response and early seedling growth of canola cultivars (Okapy, Zarfam, Talayeh, Hayola, RGS003, SLM046) to different salinity levels (0, 5, 10, 15 and 20 ds.m-1) were investigated in a randomized complete block design (RCBD) with three replications in the laboratory. The experiment was conducted in the research laboratory of the Faculty of Agriculture, the University of Birjand, during 2007. Increasing salinity level caused a significant reduction in final germination percentage, germination rate, root and shoot length, and fresh weight. The response rate, however, was different depending on the tested cultivar, and cultivar × salinity interaction was significant in the analysis of variance of all measured parameters. The functional three- parameter logistic model provided a successful estimation of the relationship between salinity and final germination response of Canola Cultivars. The highest and the lowest model slopes were observed in RGS003 and SLM046, respectively, which, in turn, indicates the highest and the lowest salt sensitivity. The fitted model showed that the salinity level that causes 50% reduction in final germination percentage was 14.5 dS.m-1 for RGS003 and 26.8 dS.m-1 for SLM046. In general, results showed the following order in salinity resistance during germination and early seedling growth: SLM046> Zarfam> Talayeh> Okapy> Hayola> RGS003. This classification depicts the salt tolerance of canola cultivars during early stages of plant growth; therefore it is essential to conduct further research for assessing this tolerance during later plant growth stages.

Soil organic matter content is low in most cultivated soils in Iran but the addition of organic wastes may improve soil physical, chemical and biological properties. One of the problems caused by using manure and compost is the high salinity and its effects on plant growth. The purpose of the present experiment was to study the effects of manure leaching on soybean (Glycine max L. var. Williams) seed properties. Treatments consisted of a factorial arrangement of three organic wastes (Esfahan's municipal compost, cow and sheep manures) in four levels (0, 1, 2 and 4 % on dry weight basis) and two leaching levels (leached or not leached) in a completely randomized design with three replicates. The findings of the paper show that compost and cow manure increased most of the nutrient concentrations in soybean seeds. But adding sheep manure just increased nitrogen and Mn concentration significantly. Application of cow manure increased seed number by 49%. Application of compost and cow manure increased seed yield by 51 and 54%, respectively. Leaching of compost and sheep manure reduced seed yield. The effect of leaching on the seed nutrients concentration was not consistent. It can be concluded that better results can obtain with fewer leaching ratios.

In order to investigate the effects of drought caused by PEG 6000 and salinity induced by NaCl on germination and seedling growth of Clary, two experiments were carried out based on a completely randomized design with 4 replications. In the first experiment, the effects of drought levels (0, -2, -4, -6, -8, -10, -12 bar) and in the second one the effects of salinity levels (0, 50, 100, 150, 200, 250, 300, 350 mmol) on germination percentage, germination rate, seedling length and seedling dry weight was studied. Effect of salinity and drought stresses were significantly different between various treatments. The maximum rates and percentage of germination were obtained at control and the minimum percentage of germination was obtained at -12 bars and 350 mmol. Water potential significantly reduced seedling length and seedling dry weight. Results showed that Clary, a medicinal plant, is highly tolerant to drought and salinity stresses during germination period.

Salinity is one of the environmental factors that have a critical influence on the emergence and plant growth and establishment. The determination of salinity tolerance threshold is a useful criterion to choose soil and irrigation water for cultivation of halophytes. In order to determine salinity tolerance threshold in Kochia, an experiment was performed in greenhouse in a complete randomized block design with five replications in two stages. In the first stage, the experiment was performed with salinity levels of 0, 10, 20, 30 and 40 dS m-1 NaCl. In this stage, seeds were able to emerge up to the salinity of 20 dS m-1 and the emergence percentage in salinity levels of 0, 10 and 20 dS m-1, was 85, 55 and 28%, respectively. In order to determine the full-scale of salinity tolerance threshold in Kochia, the second experiment was conducted. At this second stage, treatments were different levels of salinity equal to 20, 22, 24, 26 and 28 dS m-1 NaCl. Kochia seedlings were able to emerge up to the salinity of 26 dS m-1 NaCl. In general, with increasing the levels of salinity seedling emergence percentage, the length of seedling, fresh and dry weight of shoot and dry matter percentage was decreased. According to the results, salinity tolerance threshold for seedling emergence and performance of Kochia under controlled conditions was 26 dS m-1.Key words:

An experiment was conducted to study the effect of organic and inorganic antioxidant on Gompertz non-linear function in broilers reared under heat stress. So, 180 one-day old chickens (male and female) were used in a completely randomized block design with 6 treatments and 3 replicates. The experimental diets were (T1) control diet; (T2) control diet + 5 gr.kg-1 turmeric powder; (T3) control diet + 10 gr.kg-1 turmeric powder; (T4) control diet + 0.3 mg.kg-1 sodium selenite; (T5) control diet + 0.3 mg.kg-1 sodium selenite +5 gr.kg-1 turmeric powder; and (T6) control diet + 0.3 mg.kg-1 sodium selenite +10 gr.kg-1 turmeric powder. Broilers were subjected to heat stress (35 ºC) during the fifth and sixth weeks. The results showed that diets including 10 gr.kg-1 turmeric powder significantly increased final weight (Wf), weight at inflection time (Wt) and time at inflection time (t) (p<0.05). However, the difference between 10 and 5 gr.kg-1 turmeric powder levels was not significant. The interaction between selenium and sex was significant on Wf in such a way that male chickens fed with selenium had higher Wf.