Journal of Soil and Plant Interactions

---

In order to assess the effect of salinity on root traits and yield of two wheat cultivars, an experiment was conducted in Agricultural, Medical and Industrial Research School, Nuclear Science and Technology Research Institute, Karaj, Iran, using factorial experiment based on complete randomized design with 3 replications. The first factor included sensitive wheat cv. (Tajan) and tolerant cv. (Bam) and the second factor was salinity stress at four levels (6, 8, 10 and 12 dS/ m). In each treatment, 10 days after anthesis, the variation of root dry weight, shoot dry weight, root/stem ratio, and root area and volume were analyzed. The results showed significant reduction (P≤0.01) in root dry weight, root area and root volume per plant. Root/shoot dry weight ratio decreased 35.1% and 8.2% in Tajan and Bam cultivars, respectively, at 8 dS/m compared to 6 dS/m. Results revealed that grain yield per plant was affected by root dry weight, as the highest grain yield was observed in Bam cultivar. Increased grain yield in this cultivar was due to higher root dry weight. Also, Tajan cultivar had the lowest grain yield and root dry weight in 12 dS/m treatment. There were positive correlations among root surface and volume with root dry weight and therefore with grain yield. Therefore, based on the parameters studied in this experiment, it can be stated that a large part of the traits associated with sensitivity or tolerance of wheat cultivars to salinity could be attributed to their roots’ characteristics.

---

In order to study the effects of different amounts of irrigation and nitrogen levels on physiological reactions of two sorghum (Sorghum bicolor) cultivars, an experiment was performed under greenhouse conditions at Ferdowsi University of Mashhad, in 2011. Treatments were two irrigation regimes (I1, I2, consisting 100 and 40 % of field capacity, respectively), four nitrogen levels (N1, N2, N3 and N4 consisting 0, 30, 60 and 90 mg N/kg soil, respectively) and two cultivars (Sepideh and M5) arranged in randomized complete block design with three replications. The results showed that water stress significantly decreased chlorophyll a and b and increased carotene contents in sorghum cultivars. Nitrogen application had significant effect on chlorophyll a. Water treatments led to an increase ascorbat and soluble sugars contents. Water stress and nitrogen application increased prolin content of sorghum cultivars. Grain yield was affected by water stress and nitrogen treatments. The highest value of grain yield was obtained by full irrigation and 60 mgN/kg soil. Our result show that in water stress conditions, biochemical changes in sorghum were accrued such as increase activity of antioxidants, reduces the content of free radicals in cells and increase in the amount of carotenes prevents damage to the plant cells. Also in these conditions, with increasing content of osmotic adjustment and water balance of the cells, could prevent severe reduction in leaf relative water content of the cells and causes the stabilization of the cell structure. According to correlation coefficients obtained from the experiments we can conclude that in drought conditions, biochemical factors in maintaining grain yield consist of concentration of soluble carbohydrates and proline, respectively.

---

Plant roots, with respect to their intrinsic characteristics, have important role in both improvement and development of germplasms of drought resistant plants. This experiment was conducted to study direct and indirect effects of root morphological traits on grain yield of four triticale genotypes (three promising lines of ET-82-8, ET-82-15 and ET-79-17 along with the conventional Junillo-92 cultivar) under two available moisture levels in soil (irrigation after 50% moisture depletion in the root zone, as control) and moisture stress (irrigation after 80% moisture depletion in the root zone) as a randomized complete blocks design in factorial arrangement with four replications, in Research Greenhouse of College of Agriculture, Ferdowsi University, Mashhad, Iran, in 2008. The results showed that water stress caused a 9% reduction in root depth development. Also, the difference between deepest root in ET-82-15 and the shallowest root in Junillo-92 was about 8.2 cm. Delay in irrigation caused a 25% reduction in accumulated root length. The 43% difference between highest accumulated root length in ET-82-15 and lowest accumulated root length in ET-79-17 was significant at 1% level. The role of root morphology of these genotypes on seed production was different under various soil moisture conditions. In optimum soil water content, direct effect of accumulated root length with regression coefficient of 0.543 was more than water deficit conditions with regression coefficient of 0.286. On the other hand, direct relation of total root surface with grain yield was negative in normal moisture conditions and negative under water deficit. In general, it seems that accumulated root length and root surface are effective characteristics in seed production of these genotypes total root surface has more important role in water deficit conditions, and accumulated root length in optimum soil moisture levels.