Application of temperature stress to root zone of spinach III. Effective method for short term application of low and high temperature stresses to roots

Mountain streams with water temperatures lower than 10°C can be easily found in the southern part of Japan from late autumn to early summer. In this study, the potential of cool water of the mountain streams to produce value-added vegetables was examined by applying low temperature stress only to roots in a soil-less culture of spinach plants (Spinacia oleracea L.). The root treatment with a moderately low temperature of 10°C subsequent to the short term pre-treatment with a moderately high temperature of 30°C brought the moderate low temperature stress in roots and induced adaptive functions of osmoregulation and antioxidation in shoots. This effect enabled to produce value-added spinach with high contents of healthful substances (sugars, Fe, ASA and SOD) and low contents of harmful substances (NO₃^- and oxalic acid) without significant depression in growth. These results suggest the possibility of production of value-added vegetables by applying cool water of mountain streams to the root zone.