Effects of the absence of nitrogen and all nutrients at the later growth stage on the contents of sugars, ascorbic acid, nitrate and oxalic acid in spinach (Spinacia oleracea L.) under hydroponic culturing.

摘要

The effects of the absence of nitrogen and all nutrients on the contents of components related to spinach quality were investigated during the late stage of growth under hydroponic culture. Spinach plants were grown in a standard solution containing100 mg NO3-N/litre until plant height reached about 25 cm, and then transferred to either the standard solution without N (-N solution) or groundwater, for 10 days. At 8 days, the sugar and ascorbic acid contents were increased about 2-4 times and 1.3-2times, compared with plants grown in the standard solution, respectively. The nitrate content decreased by 75-90% compared with plants in the standard solution after 8 d, but oxalic acid content was not affected. With regard to spinach quality, culturein groundwater was more effective than that in the -N solution. However, when plants were grown in groundwater under high light intensity and low night temperature conditions, a physiological 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 addition of K to the water.