Response of lettuce to Cd-enriched water and irrigation frequencies

This pot experiment was an attempt to investigate a broad response of lettuce to different cadmium (Cd) levels of irrigation water (0, 5, 10 and 20 mg l-1) under different irrigation intervals (1, 2 and 4 days). The results showed that increased level of soil Cd through irrigation eventually decreased the yield of lettuce in all cases; however, in some cases yield was increased with lower doses of Cd application. No injury symptoms were observed other than plant height and yield reduction. Shoot dry weight proved to be the most sensitive parameters to the cadmium, especially under water stress conditions. The results also showed that the concentrations of nutrient elements in lettuce shoot were suppressed by water stress. The presence of cadmium in irrigation water did not significantly affect the absorption of nutrient elements by plants except for Fe. Shoot Cd concentration and its uptake decreased with increasing irrigation frequencies and the reverse trend occurred with increasing Cd levels of irrigation water. However, the values were higher than recommended guideline in all conditions. Also, shoot Cd content showed a significant positive correlation with the final accumulated Cd concentration of soil and was expressed by a plateau model under the dry irrigation regime and linear models at other irrigation intervals. Overall, shoot Cd concentration was predicted by using a simple linear regression model regardless of evapotranspiration and transpiration rate of plant.Key words: Cadmium toxicity; chemical composition; irrigation frequency; lettuce

Effect of Water Potential on Germination of Verticillum dahliae microsclerotia

The effects of osmotic and matric potentials on the microsclerotial germination of Verticillium dahliae was examined at room temperature in 1% water agar amended with sodium chloride and polyethylene glycole. Treatments consisted of 6 levels of osmotic and matric potentials (0, -0.3, -0.6, -0.9, -1.2, and -1.5 MPa) laid out as factorial arrangement in a completely randomized design. Decreasing matric potential reduced germination, whereas the osmotic potential increased germination up to -0.6 MPa but any further increase caused it to decline. It was concluded that the matric potential is a more limiting factor than the osmotic potential for the germination of V. dahliae microsclerotia

Relative efficiency of two zinc sources for maize (Zea mays L.) in two calcareous soils from an arid area of Iran*

International audienc

Deficit irrigation and nitrogen effects on nitrogen-use efficiency and grain protein of rice

To meet future food demand, world rice production must increase in the next few decades, which is possible only by effective use of soil and water resources and inputs. This research was conducted to investigate the effects of nitrogen, N, application and deficit irrigation treatments including a sprinkler, intermittent flooding and continuous flood irrigation, and their interaction with the N-use efficiency and grain protein of a local lowland rice cultivar. The results indicated that low (sprinkler irrigation) and high (continuous flood irrigation) applied water affected the plant and soil factors in N uptake and decreased N-use efficiency for rice. Therefore, optimum applied water was obtained in intermittent flooding (2-day interval). Reduction in nitrogen uptake at high applied water can be due to the effect of nitrate leaching in the root zone and the reduction in N uptake at low applied water can be due to the inability of the roots to absorb N and translocate it to the plant top. With respect to the relationship between N uptake and grain protein and leaf chlorophyll, these parameters can also be affected by applied water and N application. Appropriate linear models were proposed to show these relationships. At different times of soil nitrogen measurements and N application rates, maximum nitrogen leaching (about 50%) occurred in continuous flooding irrigation