Effects of salinity and cadmium on some growth factors and micronutrients uptake by coriander (Coriandrum sativum L.)

Growth and yield of plants in many parts of the world are completely limited due to the influence of various environmental stresses. The presence of heavy metals is one of the most important environmental stresses that can result in lowering the level of growth and crop production. The Pollution of crop productions with heavy metal not only leads to decrease in the quality of products, but also threatens the human heath through entering the food chain. Therefore, they are very important from the environmental point of view. Salinity, considered as one of the most important factors limiting the growth and crop production, is an important factor in transferring heavy metals from roots to limb plant. This is why it affects the flow of metals in the soil. Since the salinity of soil along with heavy metal pollution is considered dangerous to food security, this research was conducted to investigate the interaction of salinity stress and Cadmium on some growth factors and nutrients uptake in Coriander.
This experiment was conducted in the crop year 2014-2015 in greenhouse of Ramin Khuzestan Agricultural and Natural Resources University in factorial arrangement in a completely randomized block design with three replications. Treatments consisted of three levels of salinity of sodium chloride 2, 5 and 8 dS m-1 and Cadmium and Cadmium chloride source in 3 levels of 0, 50 and 100 mg kg-1. The seeds of coriander were transferred to the pot after germination. Before settling the coriander seeds, the specified levels of cadmium in solid form were uniformly mixed up with the soil in pots other than the control pots. Salinity treatment was applied from the beginning of the third week of planting with irrigation water. At the end of the eighth week, limb plants and plant roots were harvested. The height of each plant was measured using a ruler. In order to determine the dry weight, the envelopes containing the plant were placed in an oven for 48 hours at 75 ° C. After drying, their dry weight was measured. Elements of copper, zinc, iron and cadmium were measured by atomic absorption spectroscopy using flame atomic absorption method. The results were analyzed using SAS statistical software and Excel charts were used for plotting.
The results of statistical analysis of the data showed that there was a significant difference between the different levels of cadmium and salinity treatments and their interaction effect on the traits. The results indicated the reduction of the height, dry weight and root dry weight with the increasing concentrations of cadmium and salinity. Decreasing plant growth factors can be due to the loss of the osmotic potential of the surrounding environment in the root of the plant's root cells. This is because of the accumulation of high amounts of salt in the soil solution. Ultimately, this reduces cell division, prolongation, and differentiation. Another factor was the decrease in plant growth under less stressed conditions of CO2 stabilization. Also, under the terms of salinity and the presence of cadmium in the soil concentrations of copper, zinc and iron shoot decreased, and the concentration of cadmium increased. The occurrence of nutritional disorders due to salinity may be attributed to the changes in the absorption capacity of nutrients in the soil, competition over the absorption of nutrients, and the disruption of the transmission and distribution of elements among different organs. According to the results most of the reduction in growth factors and concentrations of Zn, Cu and Fe at the highest level of salinity (8) and the highest level of Cadmium )100 mg kg-1) was observed.
Based on the results, the presence of heavy metal cadmium in soil resulted in a further reduction of indices at all levels of salinity stress. Generally speaking, the salinity of irrigation water caused by different amounts of sodium chloride increases the bioavailability of cadmium by the plant. This is because of the formation of a complex between chlorine and cadmium ions, The simultaneous presence of two salinity stresses and cadmium in soil is not only harmful to the plant itself due to the reduction of its growth parameters, but also endangers the health of its use because of the high metal intake in these conditions.