مجله تنشهای محیطی در علوم زراعی
سال ششم شماره 2 (نیمه دوم 1392)

The effect of sodium bicarbonate (alkalinity stress) on growth, and physiological and nutritional characteristics in three leafy vegetables (lettuce, amaranth and water convolvulus) were evaluated. In order to study the deleterious effect of alkalinity stress on plants, a factorial experiment was conducted with two factors including plant with three species and sodium bicarbonate in three levels (0, 5 and 10 mM) with three replicates. Data analysis was performed in a completely randomized design. Seedlings, after transplanting into the hydroponic condition, were put under stress for one month. According to the obtained results, shoot and root dry mass showed reduction with increase of sodium bicarbonate concentration. In response to elevated sodium bicarbonate concentrations; the plant pigments, maximum quantum yield (Fv/Fm) and photosynthetic performance index (PI) decreased in all examined plant species, however the lowest decrease, were observed in water convolvulus. The highest accumulation of proline and soluble carbohydrates was observed in water convolvulus with 10 mM sodium bicarbonate, so that soluble carbohydrates in water convolvulus at 10 mM increased 227% compared to control. Increase of sodium bicarbonate concentrations leaded to decrease in K, Fe and Zn and increase in Na in shoots and roots of plants. The results showed that water convolvulus was the most tolerance species to sodium bicarbonate among the studied plants.

Salinity is a major environmental stress that drastically affects plant growth and productivity. To achieve optimal crop production in saline regions, the most appropriate, logical choice is growing salt-tolerant varieties best suited for these regions. A two year field study was conducted at two locations on saline soils of Nishabour to investigate the effect of salinity on growth and yield of 20 wheat (Triticum aestivum.L) genotypes. Two salinity levels were imposed on two silt loam soils by irrigating with saline waters. Electerical conductivities of applied waters were 4 and 6-8 d Sm-1. The experimental design was a randomized complete block with three replications. The studied genotypes were Rowshan, Siossons, Falat, 4213, Qods, 4211*, Bezostaya, 4211, Alvand, Gaspard, Cross Shahi, Gaskogn, Marvdasht, Mahdavi, M.V.17, Hirmand, Alamoot, 4209, Cross Arvand and Chamran. Results of combined analysis of variances showed that the effect of year and genotype on grain, straw and biological yields were significant (P<0.01). In site 1, grain yield of line 4211* as a highest yield was 4167 kg ha-1. Rowshan cultivar had the highest straw and biological yields equal to 7833 and 11780 kgha-1 respectively. The lowest grain yield belongned to Falat cultivar (2650 kgha-1). Siossens cultivar had the lowest straw yield (4850 kgha-1).Generally, increase of salinity decreased grain and straw yields but straw yields reduction were less than grain yields. In site 2 Rowshan cultivar had the highest grain, straw and biological yields equal to 3867, 7893 and 11850 kgha-1 respectively. Lowest yields of grain (1567kgha-1), straw (2983kgha-1) and biological (4550kgha-1) yields belonged to Cross Arvand cultivar. According to obtained grain yield it seems that Rowshan and Siossons cultivars and line 4213 in comparison with other cultivars were preferable genotypes in saline condition. Rowshan, Cross Shahi and Alvand were superior cultivars evaluated for straw production in saline condition respectively. There is genetic variation for salinity tolerance in studied wheat cultivars and lines.

To investigate the effect of planting date and salinity on yield and spike sterility of wheat (Triticum aestivum L.) cv. Bam, a field experiment was conducted at Sadouq Salinity Research Farm, National Salinity Research Center, Yazd, Iran, during 2008-2009 and 2009-2010. The experiment was arranged as split plot based on RCBD with three replicates. Treatments were sowing dates (planting at 23 Oct., 6 Nov., 21 Nov. and 6 Dec.), and saline water, ECiw= 2 (non-saline) and and 10 dS/m (saline conditions). Results showed that grain yield were not significantly different by planting date at 23 Oct., 6 Nov., 21 Nov. in both years. Delay in planting date until 6 Dec. reduced grain yield significantly by 28 and 34 percent in 2008-2009 and 2009-2010, respectively. The best planting date in order to experiment conditions was early November. Delay in planting date increased spike and spikelet sterility percent in both years. The lowest and highest spike and spikelet sterility percent was observed at 6 Nov. and 6 Dec., respectively. Spike and spikelet sterility percent was more in saline conditions than non-saline conditions. It seems any environmental stress such as salinity and delay in planting date in ZGS=40 to ZGS=49 (Booting stage), could increase spikelet sterility per spike.

One of the main aims of biosaline agriculture is the production of high quality forages by halophyte plants. Kochia is a halophyte plant which has a proper capability for forage production. Evaluation of nutritive value and anti-nutritional compounds of Kochia ecotypes under saline irrigation was the goal of this experiment. Three saline irrigation waters (5.2, 10.5 and 23.1 dS m-1) and three Iranian kochia ecotypes (Birjand, Borujerd and Sabzevar) were assigned as the main and sub plots, respectively, in a split plot design based on RCBD with three replications. The results showed that in vitro dry matter digestibility of leaf and whole aboveground organs were not affected by salinity, while in vitro stem dry matter digestibility increased under the severe salinity conditions. Organic matter digestibility of leaf, stem and whole plant at 10.5 dS m-1 were higher than other salinity levels. Crude proteins in whole plant increased by salinity but there were no significant difference among ecotypes. Increasing salinity levels decreased the percentage of neutral detergent fiber (NDF) and acid detergent fibre (ADF) in whole plant. Percentage of whole plant NDF in Sabzevar ecotype was more than other populations, but there were no significant differences among populations in whole plant ADF. The total phenol and tannin content showed an increasing trend with increased salinity levels, though it was not significant among salinity levels. Total phenol and tannin accumulation in Sabzevar population was more than other populations. Generally, kochia forage quality is comparable with other common forage crops at the beginning of anthesis stage and there were no differences between the forage quality of studied populations up to the salinity level of 23.1 dS m-1.

In Iran, vast amounts of saline lands, shortage of fresh water resources and potential of halophytes for forage production has generated a great interest in utilizing these species as a substitute for convenient forage resources. In order to introduce suitable halophyte species for forage production, an experiment was conducted on 14 halophyte species in the greenhouse and in the saline lands located at Chah-Afzal Salinity Research Station of NSRC, Yazd, Iran. In the greenhouse experiment, seedling emergence percentage and emergence rate were studied. In the saline land, 2-month old seedlings of halophyte species with high emergence percentage were planted at 1.5 ×1.5 m spacing in the form of a complete randomized block design with three replications and were irrigated with saline water (8 dS/m). All plants were harvested six months later and some characteristics including amount of seedling establishment, yield and yield components were measured. Results showed that Kochia indica produced the greatest forage fresh and dry yield (15.5 and 6.9 ton/ha, respectively). This species also had the greatest seedling emergence percentage (100%) and emergence rate (5.5 seedling per day). After that, Atriplex halimus had the greatest yield (9.7 ton/ha fresh forage and 3.5 dry forage), seedling emergence (95%) and emergence rate (4.83). Therefore, both K. indica and A. halimus are superior species for forage production under saline conditions and may be suggested for forage production and rehabilitation of rangelands under saline conditions.

In order to investigate the effect of different rates of phosphorous fertilizer on grain and oil yield and some agronomic traits of Indian mustard (Brassica juncea L.) under drought stress at early growth stage, a split plot experiment based on randomized complete block design was conducted with three replications at the Agricultural and Natural Resources Research Center of Sistan during 2009-2010 cropping season. Drought stress was assigned as the main plot factor with two levels including: 1- Non stress, where plots were irrigated from sowing to physiological maturity based on % 50 depletion of available water. 2- Vegetative phase drought stress, where plots were irrigated from sowing to flowering stage based on % 80 depletion of available water. Phosphorus fertilizer was considered as sub-plots with four levels of P1=0, P2=100, P3=150 and P4=200 kg.ha-1 (from super-phosphate triple P2O5-1). Results showed that early season drought stress (irrigation ceasing at rosette and budding to flowering stage) significantly decreased grain yield and yield components such as, number of siliques per plant, seeds per silique, 1000-grain weight, as well as plant height and oil yield traits. The greatest seed yield (3567 kg.ha-1) and oil yield (1377 kg.ha-1) were obtained at non- stress irrigation conditions. Increasing phosphorus application up to 150 kg.ha-1 increased the grain yield and most related traits, while yield reduction was observed at 200 kg.ha-1 level. The interaction effect of phosphorus application and irrigation on all traits was not significant. Amongst agronomic traits, the greatest correlation coefficients of grain yield were obtained with the number of silique on main branch (r= 0.84**), plant height (r=0.76**), silique number per plant (r= 0.74**), and 1000-seed weight (r=0.76**). Based on study results, to gain maximum grain and oil yield and yield components, water availability at vegetative growth stage (especially at budding stage) and at reproductive stage (flowering and grain filling stages) by consumption of 150 kg.ha-1 super-phosphate triple is essential in mustard.

The effect of water stress on plants is complex and can be studied from different aspects. In this regard, studying the physiological reactions can be an effective and helpful tool in identifying the drought tolerance. In order to evaluate the effect of water stress and foliar application of humic acid on photosynthetic pigments, antioxidant enzymes and biochemical compoounds (proline and soluble carbohydrates) of borage (Borago officinalis), a field experiment was conducted as a split plot design with three replications in 2012 at Agricultural Research Station, University of Zabol. Water stress levels included 90 percent of field capacity (W1) as the control, 70 percent of field capacity (W2) and 50 percent of field capacity (W3) as the main plots and four levels of humic acid foliar application including control or without humic application (H1), H2=1.5, H3=3 and H4=4.5 liter of humic acid in 1000 L water. Analysis of variance results showed that water stress had a significant effect on chlorophyll a, b, soluble carbohydrate, proline content and antioxidant enzymes, ascorbate peroxidase (APX) and gaycol peroxidase (GPX) in green leaves of borage plants. By increasing levels of water stress from control to W3, the carbohydrate content as well as APX and GPX activities increased and the amounts of chlorophyll a and b decreased. Meanwhile the increased concentration of proline only happened until W2 treatment. Humic acid treatment at different levels of water stress had a significant and positive influence on all of the above studied factors except CAT enzyme, chlorophyll b and carotenoid pigments. The maximum effect of humic acid at the most severe water stress level (W3) was obtained by foliar application of 1.5 and 3 liter of humic acid and this treatment had the most impact on the osmotic adjustment, photosynthesis pigments and APX antioxidant enzymes, which was very effective in drought tolerance.

Nowadays, it is clear that the nuclear techniques especially gamma radiation play an important role in production of resistance plants to salinity.These experiments were conducted in two phases. First of which is germination in a factorial based on completely randomized design and second of which is seedling growth in a factorial based on randomized complete block design (RCBD) with three replications at the Faculty of Agriculture in Birjand University. We used three kinds of Safflower cultivars namely Isfahan14, KW9, IL111 and six gamma rays at 0, 50 100, 200, 300, and 400 Gy and five salinity levels of 0, 3, 6, 9 and 12 dsm-1. Experimental results showed that the response of safflower against gamma radiation and salinity varied. Salinity decreased root and shoot length, root and shoot dry weight, leaf number and area, and stomatal conductance. Root dry weight at the dose of 50 Gy and salinity levels of 3 and 6 dsm-1 and at 100 Gy at all salinity levels increased. Gamma irradiation doses of 300 and 400 Gy decreased root and shoot growth characteristics of safflower. According to the results of the experiment, it can be concluded that doses less than 200 Gy in safflower are capable of producing salt- resistance crop.

Salinity caused by sodium chlorides alters the ion balance and nutrient status of a plant. Therefore in order to investigate the effect of different levels of salinity on germination and seedling growth traits of blue panic grass (Panicum antidotal L.) an experiment was conducted in completely randomized design with four replications during 2011 growing season under green house conditions. Salinity applied at germination stage using five levels of 0, 2.5, 5, 7.5 and 10 dS m-1 with four replications. Germination indices were reduced by increasing salinity, so that a severe reduction happened at 2.5 dS m-1 (47% reduction in germination percentage compared to the control) and it was reached its lowest value at 10 dS m-1 (89% reduction in germination percentage compared to the control). The experiment at seedling stage included five salinity levels (0, 2.5, 5, 7.5 and 10 dS m-1) with three replications. This stage included three parts: 1- salinity application before emergence, 2- salinity application before emergence and 3- salinity application from planting until four leaf stage. At this stage, plant leaf area, root and stem dry weight and root to shoot ratio were significantly affected by salinity levels. At the second part of second experiment, root to shoot ratio increased at the salinity of 5 dS m-1 (i.e. 0.62 but for the control was 0.44). Overall results showed that blue panic grass was more sensitive to salinity at germination stage compared with seedling stage.