نشریه روابط خاک و گیاه
پیاپی 5 (بهار 1390)

Identification of growth and development pattern of plant organs, especially the roots, is important to optimal management of halophytes production. In this study, blue panic grass (Panicum antidotale Retz.) was planted in a sandy loam soil in plastic tubes and 4-leaf seedlings were exposed to different levels of irrigation water salinities including 0, 10, 20, and 30 dS/m. These salinity levels were produced by dissolving 0, 5, 11, and 20 g of NaCl in one liter of distilled water. In order to investigate the pattern and development rate of different root components, morphological attributes of roots were measured at four stages including beginning of tillering, stem elongation, panicle emergence and seed ripening. Thereafter, the best equations were selected to express the trend of measured root characteristics with time via regression method. The results showed that with increasing the plant age and development of photosynthesis structures, the rate of increase in root weight in non-saline conditions reached to about 70 mg per day at the stem elongation stage. During this period, the rate of root weight increase at the 10, 20 and 30 dS/m salinity levels was 30, 60 and 40 mg/day per plant, respectively. The rate of root weight increase was reduced at different levels of salinity during stem elongation and panicle emergence stages. This reduction was significant at the 10 and 20 dS/m salinity levels. Also, the assimilates allocated to the roots during the seed planting to the beginning of tillering (0-18 days after planting) was about 25, 22, 9 and 10% at the 0, 10, 20 and 30 dS/m salinity levels, respectively. However, the assimilates allocated to the roots at stem elongation (18-35 days after planting) were 34, 21, 25 and 26% at 0, 10, 20 and 30 dS/m salinity levels, respectively. Salinity affected sigmoid development pattern of this plant’s roots by reducing the rate of development and size of its components, although different root characteristics showed various sensitivities to irrigation water salinity.

In this study, the effect of nitrate to ammonium ratio and pH of nutrient solution on the changes in pH and EC of rhizosphere during spinach growth period in perlite culture, under greenhouse conditions, was investigated. A split factorial experiment in a completely randomized design with four replications was conducted with three factors including nutrient solution’s pH in three levels (4.5, 6.5 and 8), nitrate to ammonium ratio of nutrient solution in five levels (100:0, 75:25, 50:50, 25:75 and 0:100) and 10 levels of time. Three seedlings of spinach plant (Spinacia oleracea L. cv. Sirius) were cultivated per pot and nourished with 15 different nutrient solutions. During the growth period and at different times, the leachate pH and EC of cultivated and uncultivated pots were measured. The results showed that the effects of time, pH and nitrate to ammonium ratio of nutrient solution on pH and EC of rhizosphere were significant (P<0.001). By increasing the nitrate to ammonium ratio of nutrient solution, the pH of rhizosphere was increased but the EC of rhizosphere was decreased. At the end of the growth period, the pH of rhizosphere in the nitrate to ammonium ratio of 100:0 was about three units higher than the nitrate to ammonium ratio of 0:100 and two pH of 4.5 and 8. While, this difference was lower at the pH of 6.5. During the spinach plant growth period, the changes in pH and EC of rhizosphere in studied treatments were different. In the nitrate to ammonium ratio of 75:25 and pH of 6.5, the pH of rhizosphere was in the optimum range for plant growth and nutrients uptake. Except in the nitrate to ammonium ratio of 100:0 and pH of 8, in the rest of the treatments, the rhizosphere pH decreased during plant growth period. The initial pH of nutrient solution had different effects on the rhizosphere pH. The average rhizosphere pH in nutrient solutions with pH of 4.5, 6.5 and 8 was 5.94, 6.5 and 7.29, respectively. The results showed that in adaptation to adverse acidic or alkaline conditions, the spinach plant changes its rhizosphere pH actively. Also, undesirable effects of pH on the spinach growth in adverse acidic or alkaline conditions can be decreased with application of proper nitrate to ammonium ratio. The rhizosphere EC was more than the leachate EC of uncultivated pots and the initial EC of nutrient solution. By decreasing the pH of nutrient solution, the rhizosphere EC of spinach was increased.

Although nickel (Ni) is known as an essential element for higher plants, the biological effects of this nutrient on growth, yield, and N metabolism of some plants, particularly leafy vegetables, is still unknown. Therefore, this study was carried out to investigate the effects of Ni and urea nutrition on the growth and yield of lettuce (Lactuca sativa L. cv. Baker) and urea accumulation in plant tissues. In this study, nitrogen was supplied from the source of urea or ammonium nitrate at three levels (5, 10 and 20 mM) and Ni was supplied in the form of NiCl2 at two levels (0 and 0.04 µM). The plants were harvested 6 weeks after transplanting and the fresh weight of shoots and roots were determined. The shoots urea concentration and activity of urease enzyme in the leaves were also measured. The results indicated that shoots fresh weight of the urea-fed plants increased with increasing urea concentration in the nutrient solution. Addition of Ni to the nutrient solution significantly promoted the root and shoots fresh weight of urea-fed plants, regardless of N level. Ni nutrition significantly increased the urease activity in the lettuce leaves and as a result, reduced urea accumulation in the shoots and toxicity effects of urea. Therefore, it seems that urea in combination with Ni can successfully be used in production of lettuce in soilless culture systems.

In order to study of the effect of substrates on vegetative and ecophysiological characteristics of coleus plant, coleus cuttings containing two leaves were planted in perlite, cocopeat, peatmoss, compost, 50% perlite + 50% cocopeat, 50% perlite + 50% peatmoss, 50% perlite + 50% compost, 5% cocopeat+50% peatmoss, 50% cocopeat + 50% compost and 50% peatmoss + 50% compost with four replicates. Cuttings were irrigated by hydroponic solution after root formation. Results indicated that the highest root fresh and dry weight was observed in 50% perlite + 50% compost treatment, the highest secondary roots in perlite treatment, and the longest root and stem, the most fresh and dry weight of shoot, number of leaves and photosynthesis were observed in peatmoss treatment. Result showed that the best substrate for growth and development of coleus plant is peatmoss.

The class A pan method has been one of the most popular methods due to its simplicity, relatively low cost, and producing daily evapotranspiration estimates. Because of the large area occupied by a class A pan, alternative methods have been sought to estimate ETo inside greenhouses. With the objective of evaluating the performance of evaporation pan in estimating the water consumption in greenhouse, one class A pan and one reduced pan installed inside the greenhouse and another class A pan was installed outside. In this research three drainage lysimeters indoor and three weighing microlysimeters for indoor and outdoor the greenhouse were used to determine the reference evapotranspiration. Coefficients of pans were obtained by comparing of the evaporation pans values with the data of the lysimeters. The results indicated the monthly evaporation values measured by the class A pan and reduced pan, (both inside the greenhouse) with the data of the lysimeters, R2 was obtained 0.974 for the class A pan method, and 0.982 for the reduced pan method. Also with comparing between the monthly evaporation values measured by the class A pan outside the glasshouse and the data of the lysimeters inside, R2 was obtained 0.756. Considering the high coefficients of correlation inside the glasshouse, it is possible to replace the class A pan outside with the class A pan and reduced pan inside to estimate ETo. Reduced pan has a low cost and is easy to use and also occupied a small area in the greenhouse, therefore it is recommend to replace instead of class A pan inside the greenhouse.

In order to study the effect of gamma irradiation on biochemical characteristics of two wheat genotypes, a greenhouse experiment was conducted in 2009 in Agricultural, Medical and Industrial Research Institute, Karaj, using factorial experiment based on complete randomized design with 3 replications. Two wheat genotypes (Roshan and T-65-58-8) were irradiated by 100, 200, 300 and 400 Gy. The non-irradiated seeds of each genotype were considered as control. Irradiated Seeds were immediately row-planted in the soil blocks. Samples for various assays and estimation were taken from flag leaves on the 7th day after anthesis. Results showed that Roshan seeds were unable to germinate at 300 and 400 Gy doses. The average MDA content was increased with various doses of gamma radiation in two genotypes. But in Roshan genotype, the MDA content was higher as compared to T-65-58-8. In both genotypes, the chlorophyll content was increased at 100 Gy and the highest amount of proline and soluble sugars were obtained at 200 Gy. Biochemical differentiation based on total soluble protein content revealed that T-65-58-8 and Roshan genotypes at irradiation dose of 200 Gy contained the lowest (28.91 Ug/gFw) and the highest (70.98 Ug/gFw) amount of total soluble protein, respectively. Severe increase in specific activity of peroxidase enzyme was observed as the gamma dosage increased. It seems that Roshan wheat cultivar was more sensitive to irradiation stress than T-65-58-8 line. Also, in irradiated treatments, the 100 and 200 Gy doses caused positive variations in the studied biochemical indices. It was concluded that protein and chlorophyll, soluble protein and MDA contents may be used in early assessment of effective radiation doses to induce mutations in wheat genotypes.