فصلنامه علوم زراعی ایران
سال هجدهم شماره 4 (پیاپی 72، زمستان 1395)

To study effects of different levels of nitrogen fertilizer and cytokinin on some physiological traits of wheat cv. Chamran under normal and post anthesis heat stress conditions, this experiment was conducted at Ramin Agriculture and Natural Resources University, Ahvaz, Iran, in 2012-2013 growing season. The experiment was carried out in two separate factorial experiments using randomized complete block design with four replications.The first experiment was planted in normal date of sowing (05 December 2012) and the second experiment was planted late (20 January 2013) to expose the experimental treatments to terminal heat stress. In both experiments, nitrogen (N) was applied at four levels (0, 75, 150, and 225 kg.ha-1) and cytokinin (Ck) at three levels (0, 50 and 100 µmol). Results showed that intraction effect of sowing date× nitrogen× cytokinin on prolin content and SPAD value, intraction effects of nitrogen × cytokinin and sowing date × nitrogen on FLAD (Flag Leaf Area Duration), stomatal conductance and grain yield was significant. The highest grain yield was obtained from application of 150 kg.ha-1 nitrogen and 100 µmol cytokinin, however, it was not significantly different from 225 kg.ha-1 nitrogen and 100 µmol cytokinin and 150 kg.ha-1 nitrogen and 50 µmol cytokinin. It was concluded that with increasing application levels of nitrogen and cytokinin the negative effects of terminal heat stress could be mitigated.

Genotype × environment interaction (GEI) effect is very important for plant breeders. Identifying the GEI effect would help breeders for better evaluation of different genotypes and select the superior genotypes based on both high grain yield and its stability. In this study, thirteen advanced rice genotypes orignated fromthe Iranian local rice varieties including two local rice cultivars (Hashemi and Saleh) as checks were evaluated in randomized complete block design with three replications at three locations (Rasht, Abkenar and Chaparsar) in two rice growing seasons (2014-2015). Analysis of variance indicated significant differences among rice genotypes for grain yield in three locations. GGE biplot analysis revealed that the first principal component (PC1) explained 77% of the total variation while PC2 explained 20%. Thus, the two components together accounted for 97% of the G GE variation for the grain yield in all environments. Two distinct mega-environments were also identified. The first mega-environment included; Rasht and Abkenar in which genotypes RI18430-47, RI18430-56, RI18430-87, RI18430-12 and RI18430-72 were the winners. The second mega-environment included; Chaparsar in which genotype RI18430-77 was the winner. RI18430-12 and RI18430-47 genotypes were selected as superior genotypes for their higher grain yield and its stability, intermediate amylose content, early maturity, suitable plant height, high head rice recovery and lower breakage. These two genotypes have been obtained from crossing between Saleh (improved cultivar) as a female parent and Hashemi (local) as male parent. Considering phenotypic characteritics, RI18430-12 was similar to the local rice variety with long grains and short black awns. The cooking quality of this line was as good as as local rice cultivars such as Hashemi and Domsiah. However, RI18430-47 genotype was similar to Saleh cultivar with bold and long grains. RI18430-47 has short awns and its grain quality with intermediate amylose content is better than Saleh cultivar, but lower than Hasehmi. Plant height of these two selected rice genotypes are short, and could be classified in early to medium maturity groups.

Salinity is one of the major abiotic stresses that affects physiological functions of plants and significantly reduces crop growth and yield. In this greenhouse experiment, effect of salt stress (Control and 150 mM NaCl) on some physiological traits and ions distribution in roots and leaf 3 blade of four wheat cultivars; Roshan, Bam, Qods and Atrak, and its association with salt tolerance in seedling stage, was studied in a factorial experiment using completely randomized design with three replications during 2014-2015 in College of Agriculture, Shahid Chamran University of Ahvaz, Iran. Results showed that sodium concentration in the roots remains higher than that of the leaf 3 blade. Salt stress significantly decreased stomatal conductance (42%), relative water content (10%), relative growth rate (24%), leaf area (33%), and root length (37%) when compared with the control. Salt-tolerant cultivars, Roshan, Bam and Atrak showed higher stomatal conductance, relative water content, relative growth rate, leaf area and root length in salt treatments when compared to cv. Qods which is salt sensitive. A significant correlation was found between physiological traits and ion distribution in root and leaf blade. Salt-tolerant cultivars sequestered higher sodium concentration in root and higher potassium in leaves. It implies that this ion distribution in root and leaves contributed to the salt tolerance in tolerant cultivars. This preferential sodium accumulation and maintenance in roots relative to shoots can be interpreted as a mechanism of salt tolerance which facilitates osmotic water uptake into the roots and restricts the transportation of sodium to shoots.

Effect of nitrogen fertilizer and plant density on root yield, quality and physiological traits of sugar beet (cv. Pars) under tape-drip irrigation condition was assessed in strip factorial plot arrangement using randomized complete block design with four replications. Two levels of planting patterns (40-60 cm and 40-50 cm) and four levels of nitrogen fertilizer; zero (N0), 50% (N1), 75% (N2) and 100% (N3) of the recommended levles for furrow irrigation) were assigned to vertical plots and two levels of row spacing (14 and 20 cm) randomized in horizontal plots. The experiment was carried out in two succeive sugar beet growing seasons (2013 and 2014) in the research field station of of Sugar Beet Research Institute, Karaj, Iran. Nitrogen fertilizer had significant effect on root and sugar yields. Decreasing nitrogen fertilizer to 75% of recommendation didn’t significantly influence root and sugar yields. The least and highest nitrogen accumulation of 99.9 and 240.3 kg.ha-1 were measured at zero and 100% levels of recommended nitrogen fertilizer, respectively. Accumulated nitrogen was partitioned greater in roots (58%) than shoots (42%). The highest Nitrogen Use Efficiency (NUE) for producing sugar was 50.8 (50.8 kg of sugar.kg-1 of nitrogen) in the treatment without nitrogen fertilizer application which was 21.7, 24.8 and 31.3 percent higher than treatments with 50%, 75% and 100% of recommended nitrogen fertilizer, respectively. Radiation penetration under the canopy showed that more radiation was intercepted in denser plant population and higher nitrogen fertilizer applications. Nitrogen fertilizer had significant effect on physiological traits such as SPAD value, chlorophyll content, maximum photochemical efficiency of photosystem II (Fv/Fm) and number of leaves. It was concluded that tape-drip irrigation system could reduce 25% of nitrogen fertilizer application without significant changes in important qualitative, quantitative and physiological traits of sugar beet.

To investigate the effect of plant density on growth indices and photosynthesis of three henna (Lowsonia inermis L.) ecotypes a factorial experiment using randomized complete block design with three replications was carried out in the Shahdad region in Kerman province of Iran in 2015-2016. Three henna ecotypes (Bam, Shahdad and Roodbar) and four plant densities (100, 50, 33 and 25 plant.m-2 equivalent to on row spacing of 5, 10, 15 and 20 cm, respectively) were evaluated as the first and second experimenatl factors, respectively. Growth indices, net photosynthesis, transpiration rate and stomatal conductance were measured and analyzed. The results showed that ecotypes were significantly different for all measured traits except leaf area index (LAI), leaf area ratio (LAR) and leaf area duration (LAD). The highest averages of the measured traits belonged to Shahdad ecotype. A significant difference was observed between the levels of plant densities for all measured traits except for specific leaf area (SLA). The ecotype and plant density interaction had significant effect on leaf area duration (LAD), biomass duration (BMD) and transpiration rate. Consequently, the highest leaf dry yield (economically valuable part of the plant) was obtained from the Shahdad (508.2 g.m-2) and Roodbar (506.4 g.m-2) ecotypes and plant density of 100 plant.m-2 (738.6 g.m-2). It can be concluded that 100 plant.m-2 is the most suitable plant density for henna in the first year of planting.

This experiment was carried out to identify drought tolerant genotypes in a set of 40 rice genotypes. Experimental materials were tested in two experiments including; a; pot experiment carried out on 40 local and improved rice genotypes under two conditions of non-stressed and water stressed (water withholding at booting stage), and b; field experiment with 17 selected rice genotypes from pot experiment using tolerance indices, at Rice Research Institute of Iran in 2014-15 rice growing season. These genotypes were tested under field conditions under normal (fully irrigated till the end of crop life cycle) and stress condition (water withholding at panicle initiation stage, till the end of crop life cycle). Results of the field experiment showed that two rice genotypes; Nemat and Pardis with 4831 and 2076 kg.ha-1 had highest and lowest paddy yield in the non-stressed condition, respectively. In watered stress condition, the highest paddy yield obtained from Sahel (3605 kg.ha-1) and the lowest yield recorded from Ali Kazemi (1179 kg.ha-1). In drought stress conditions in the second year, paddy yield was reduced by 11.5% in Sahel to 64% in Ali Kazemi cultivars. Cluster analysis could classify 17 rice genotypes iin two groups and among them13 genotypes had higher stress tolerance indices. Using ranking method and biplot based on principle components analyisi, 9 and 7 genotypes were identified as tolerant, respectively. Dorfak, Ghaem, Line 831, Ahlami Tarom and Jelodar genotypes were identified as drought stress tolerant genotypes.