| heal.abstract |
The growth and relative potassium (K+) absorption of cucumber plants when grown in unequal distribution of NaCl-induced salinity, was studied. The plants were grown in a closed hydroponic system (NFT), after splitting of their root system in two compartments. The experiment consisted of three treatments: in the first treatment (A, control) both compartments of the root were supplied with standard nutrient solution of electrical conductivity of 2 dS m-1. In the second treatment (B) the half of the root system was supplied with the above standard nutrient solution, while the other half of the root system was supplied with saline nutrient solution (standard nutrient solution + 40 mmol/L NaCl) of 6 dS m-1 electrical conductivity, in which Rubidium (Rb) was added (used as a tracer to examine K+ uptake from the saline compartment). In the third treatment (C) both compartments of the root system were supplied with saline nutrient solution (standard nutrient solution + 40 mmol/L NaCl) of 6 dS m-1 electrical conductivity, while in one of the compartments Rb was added (used as a tracer to verify the relative rate of Rb/K+ uptake). The results indicate that in the exposure of both root compartments in salinity resulted in a significant reduction of leaf area and yield, the growth of root system in both compartments was equal to the control treatment, and the absorption of Rb+ and K+ was at the same ratio. The use of a standard nutrient solution to one compartment of the root system alleviated the effects of salinity, with regard to the leaf area and yield. The part of the root system which was supplied with the standard nutrient solution had the double dry weight, compared to the part of the root which was in the saline nutrient solution; however the sum of the root dry weight in both compartments did not varied from that in the control treatment. The Rb+ tracer revealed that most of the K + was absorbed from the root part that was in the standard nutrient solution. Potassium concentration in leaf tissue was not significantly affected by salinity. The unequal distribution of NaCl salinity in the root zone allows a low Na+/K+ ratio in plant tissues. |
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