Abstract
The effects of the absence of nitrogen and all nutrients on the contents of the components related to the quality of spinach were investigated at the later growth stage under hydroponic culturing. Spinach was grown in a standard solution containing 100 mg L^<-1> NO_3-N until plant height became about 25 cm, and then transferred to the following solutions for 10 d : (1)nitrogen was removed from the standard solution (-N solution) or (2) the standard solution was exchenged for groundwater. Al 8 d after the treatment, the contents of sugars and ascorbic acid in spinach were increased about 2-4 tmles and 1.3-2 times as compared with those grown in the standard solution, respectively. The content of nitrate was decreased about 75-90% of the standard solution after 8 d, but oxalic acid was not changed. On the quality of spinach, treatment of groundwater was more effective than that of -N solution. However, when plants were grown in groundwater under a higher light intensity and low night temperature conditions, a physioological disorder appeared in the leaves, in which Na and Ca contents were increased and K content was decreased. This disorder was avoided completely by the addilion of K to the water.
