Response of cucumber (Cucumis sativus L.) to an unequal distribution of salts in the root environment

Plant response to salinity as affected by an unequal distribution of salts in the root environment was studied with cucumber (Cucumis sativus L.) as a test crop. In a series of six experiments use was made of a split root system, in which the plants were grown in separated rockwool strips irrigated with nutrient solutions with equal or different EC values, predetermined by different concentrations of either nutrients or NaCl. From low to standard EC values the uptake of nutrients was highest in the root parts with the highest concentration of nutrients. In root parts with concentrations of nutrients >4 dS m-1, the uptake decreased rather quickly. Nutrient uptake from one root part with high NaCl concentrations was also retarded, if the NaCl concentration supplied to the other root part was low. If both root parts were supplied with high NaCl concentrations, the plant was able to adjust and absorbed adequate amounts of nutrients, despite the high NaCl concentrations. Water was preferably absorbed from the root part with the lowest EC. However, if no nutrients were supplied in one of the root parts the water uptake from that root part was retarded. Effects of high NaCl concentrations in specifically retarding the water uptake were not established from the data of the experiments. The results are discussed in relation to existing models predicting effects of spatial variation of salinity in the root environment under growing conditions in the glasshouse industry and in relation to the experiences previously gained with tomato.