RELEASE OF A RESPIRATION-STIMULATING FACTOR FROM INTACT PLANT-ROOTS INTO AMBIENT SOLUTION

Respiration of roots of intact pumpkin (Cucurbita pepo L.) plants was investigated by a modified method of measuring the rate of O-2 uptake. The intact and wounded roots were found to release a respiration-stim ulating factor into the external solution. This factor stimulated root respiration not only in plants of the same species but in other plant species as well. The release of the stimulator was comparatively high in plants grown under continuous illumination and was almost absent i n darkened ones. The causes of this effect are discussed.