فصلنامه اکوفیزیولوژی گیاهان زراعی
پیاپی 21 (بهار 1391)

In order to study the effects of seeding rates on yield and yield components of three bread wheat cultivars¡ a factorial experiment based on randomized complete block design (RCBD) with 3 replications was conducted during 2006-2007¡ in Sarableh town¡ Ilam province¡ Iran. Three cultivars¡ were Chamran¡ Chanab¡ and Falat and four seeding rates were 200¡ 300¡ 400¡ and 500 seeds per m2. Results showed that¡ the differences among cultivars and seeding rates were significant for 1000 seeds weight¡ harvest index¡ and phenological traits¡ using 400 seeds per m2. Chamrans produced highest harvest index and Chanab at seeding rate of 200 seeds per m2 had the lowest harvest index. Falat produced the highest seed yield (5600 kg/ha) at 400 seeds per m2 and Chanab the lowest seed yield (3800 kg/ha) at 500 seeds per m2. The highest correlation coefficients were observed between seed yield¡ harvest index (r=0.84**)¡ seed numbers per spike (r=0.79**) and 1000 seeds weight (r=0.59*).

This study was conducted at Ardabil Agriculture and Natural Resources Research Station during the year of 2010. A factorial experiment based on randomized complete block design with four replications and two factors were used to evaluate the effect of simulated hail damage to foliage at different growth stages of potato Agria cultivar on marketable tuber yield. The first factor consisted of six levels of foliar damage (0, 20, 40, 60, 80 and 100 percent) and the second factor of five levels of plant growth stages (2, 5, 8, 11 and 15 weeks after the growing). Analysis of variance showed that there were significant differences among plants for levels and times of hail damage and their interactions in terms of marketable tuber yield. Percentage of marketable yield reduction at early stages of vegetative growth (2 weeks after growing) was minimal. Occurrence of hail damage at the tuberization and bulking stages (5, 8 and 11 weeks after growing) severely reduced marketable tuber yield. While, its damage at late growing stages of (14 weeks after growing) on tuber yield was not appreciable. Times of hail damage on marketable tuber yield reduction was calculated through the regression. Relative reduction of marketable tuber yield at the early stages of vegetative growth, due to hail damage, against non-marketable tuber yield was higher than of bulking stage.

The allelopathic effects of leaves at rosette stage of the hoary alyssum (Berteroa incana L.) against some associated grasses like, prairie June grass (Koeleria macrantha), Idaho fescue (Festuca idahoensis), blue-bunch wheatgrass (Pseudoroegneria spicata) and cheat grass (Bromus tectorum) and its own were investigated. The experiment al materials used were the leaf extracts and its allelopathic effects on seed germination and seedling emergence of the abave mentioned grasses in Petri dishes. According to our study, leaves of hoary alyssum rosettes at stage have the potential to reduce germination rate, root and shoot growth of pasture grasses and hoary alyssum itself due to its allelopathic effect. The leaf leachate solution bioassays also showed that the germination of cheat grass was more susceptible to 4% solution of allelopathic extract of leaves. Hoary alyssum leaf extract also exhibited allelopathic self-inhibition, in both seedling root and shoot growth at 2 and 4% concentrations. Self- inhibitory allelopathic effects of hoary alyssum could also be important in preventing seed germination and seedling establishment of neighboring plant.

Iran is one of arid and semi-arid regions of the world. Wheat as a strategic agricultural products faces water deficiency in most areas of the country. Therefore, identification of the resistant varieties to drought stress is one of main aims for breeders. To assess effect of drought stress at heading on 72 spring wheat recombinant inbred lines derived from American Yecora Rojo (high yielder, dwarf and early maturity) as paternal parent and Iranian No. 49 line (tall and late maturiting) as maternal parent cross were studied. The experiment was conducted at the Research Station of the University of Tabriz using a randomized complete block design with two replications during 2009 growing season. Based on the results from combined analysis of variance significant difference was observed among lines for all of traits studied, except for harvest index, grain number per spike and days to heading. There was significant difference between normal and drought stress conditions. Since the interaction between line and conditions was insignificant for all traits, it does therefore, provide the possibility of comparing the lines without regard to irrigation levels. Based on the means of, the traits it was found that the lines 96, 122, 123 and 155 were superior. MP, GMP and STI indices were recognized to be suitable indices to identify superior lines. With respect to these indices, lines 96, 122, 123, 138, 149 and 155 were found superior as compared with remaining lines. Based on stepwise regression analysis of grain yield with other traits, respectively grain number per spike, number of spikes/m2 and 1000 kernel weight were inserted into final model as effective variables on grain yield, which made 81/9 percent of the grain yield variation. Path analysis of grain yield and related traits, based on stepwise regression, demonstrated the significant positive direct effect for grain number per spike, number of spikes/m2 and 1000 kernel weight on grain yield. Cluster analysis, also showed that, lines under study were grouped into two clusters; superior lines for studied traits assigned to group one.

To evaluate the efficacy of a new herbicide Foramsulfuron ⇚Ⲻ埮꺉 (Maister OD) against other herbicides in corn fields, this experiment was fulfielld in 2010 at Mahidasht, Research Center of Agriculture and Natural Resources of Kermanshah, Iran. It was concucted in randomized complete block design with four replications and 11 treatments. In this experiment, three doses of herbicides (38.75, 46.5 and 54.25 g/ha) including foramsulfuron idosulfuron along with Nicusulfuron, ForamSulfuron, Rimsulfuron, Foramsulfuron Rimsulfuron , Bromicid hand weeding narrow leaf weeds, Bromicid Nicusulfuron and U46 hand weeding of narrow leaf weeds and a complete weeding as the control treatments were investigated. Weeds present in the field were Xanthium stromarium,Chenopedium album, Portulaca oleracea, Sorgum halepense and Setaria virdis. The results of this study showed that doses 38.75 and 46.5 g/ha of herbicide foramsulfuron idosulfuron after treatments of Bromicid Nicusulfuron and, Bromicid narrow leaf weed, hand weeding respectively could control 90 and 86 % of weeds in corn field and increase its yields significantly. Because there are presently few registered herbicide available in Iran, necessity of finding proper herbicides to control weeds in corn field and based on the results oblained from this experiment it seems using 46.5 and 38-75 grams per hectare respectively of foramsulfuron idosulfuron could be a better option than other herbicides to control weeds in corn fields and increase its seed yield.

The effects of seed priming of borage (Borago officinalis)with salicylic acid on improving its seedling traits was investigated under field condition in a complete randomized block design. Treatments consisted of untreated seeds as control, hydropriming and treatment with 500, 1000, 1500 and 2000 μM salicylic acid. Results showed that priming with salicylic acid significantly improved mean emergence time, emergence percent and index, fresh and dry weight of seedling, leaf area, leaf area ratio and specific leaf weight, but it did not affect seedling fresh weight to dry weight ratio. The highest emergence index and specific leaf weight and lowest mean emergence time (emergence rate) and leaf area ratio was found in plants which their seed were primed with 500 μM salicylic acid. It seems that seed priming with salicylic acid increased seedling dry weight more than leaf area. It was also revealed that treating seeds with the highest levels of salicylic acids resulted in negative effects on the traits measured. The lowest emergence index, emergence percent, fresh and dry weight of seedling and specific leaf weight and highest mean emergence time and leaf area ratio oblained from seedlings which primed with 2000 μM salicylic acid and followed by control and hydroprim treatments. It can be concluded that, priming with proper concentration of salicylic acid was more effective than hydropriming.

The aim of this study, was to evaluate the effect of winter cover crop residues on speed of seed potato emergence and percentage of organic carbon, soil specific weight and soil temperature. An experiment was carried out at the Research Farm of Agriculture Faculty, Bu-AliSinaUniversity, in 2008-2009. The experiment was a randomized complete block design with three replications. Winter cover crops consisted of rye, barley and oilseed rape, each one with common plant density (rye and barley at 190 kg.ha-1 and oilseed rape at 9 kg.ha-1) and triple plant densities(rye and barley 570 kg.ha-1 and oilseed rape, 27 kg.ha-1) and control (without cover crop). The results showed that rye and barley with triple plant densities produced higher biomass (1503.5 and 1392.2 g/m2, respectively) than other treatments.Soil physicochemical properties were affected significantly by using cover crops. Rye, barley, and oilseed rape with triple rate and rye with common rape of plant densities produced, the highest organic carbon. Green manure of rye and barley with triple and rye with common rate plant densities, reduced soil specific weights by 17.3, 18 and 18 percent as compared with the control treatment (without cover crop planting). Rye and barley with triple plant densities increased average soil temperature by 12 and 11 percent respectively in comparison with control treatment. These treatments increased speed of seed potato emergence by 20 and 12 percent respectively as compared with that of control treatment, respectively. Other treatments showed no significant difference as compared to control. Cover crop residues increased plants speed of seed potato emergence through improving soil conditions.

In order to study the effect of plant density, planting pattern and herbicide dosage of nicosulfuron, a field experiment was arranged in a factorial split plot treatments based on RCBD with three replications in Chenaran, Khorasan Razavi, in 2010. The experimental treatments consisted of a factorial plant density (100000, 120000 and 140000 plants ha-1) in the planting pattern (single and double row) as main plot and herbicide dosage of nicousulforon in four levels (0, 1, 1/5 and 2, l.ha-1) as sub-plot. Samplings were made at in five stages (37days after the emergence of corn and it was repeated once per 20 days). The results indicated reducing the weed density and dry matter of weeds in the first stage after the herbicide treatment. Moreover, it was observed a significant interaction effect between plant density with planting pattern and between planting pattern with herbicides dosages during growth season on reducing weed density and dry matter. Also results indicated that in between of this experiment's treatments, nicosulfuron herbicide reduced weed density at the beginning of growth season and double row planting pattern suppressed weed density during growing season, and resulted in lowest Jacard similarity index (Sj) of weed species. Results also indicated that with increasing of plant density and herbicide dosage especially in composition of double row planting pattern, according to Shannon- Wiener index, sensitive population such as common purslane (Portulaca oleracea L.), buckhorn plantain (Plantago lanceolata L.), prostrate knotweed (Polygonum aviculareL.), black nightshade (Solanum nigrum L.) and Johnson grass (Sorghum halepens L.) was reduced in during growing season. Simpson dominance index, showed that some low populated weeds such as redroot pigweed (Amaranthus retroflexus L.), common lambsquarters (Chenopodium album L.), field bindweed (Convolvulus arvensis L.) and Canada thistle (Circum arvensis L.) persisted their growth up to the end of growing season.