Effects of High Air and Soil Temperature Stress on Growth and Tuberization in Solanum tuberosum*

Potato plants (Solanum tuberosum L.) were grown at different air and soil temperatures to determine the effects of high-temperature stress on root, tuber, and shoot growth. Cooling the soil (17–27 °C) at high air temperatures (30–40 °C) relieved none of the visible symptoms of heat stress on shoot growth; nor was the degree of induction to tuberize in leaves increased, as reflected in tuberization of leaf-bud cuttings. Heating the soil (27–35 °C) at cool (17–27 °C) air temperatures had no apparent detrimental effect on shoot growth or induction of leaves to tuberize. However, in each case hot soil largely eliminated tuber development. In one experiment stolons grew up out of the hot soil and formed aerial tubers upon reaching the cool air. When leaf-bud cuttings from induced plants were used as a model system, high soil temperatures inhibited tuber development from the buried leaf buds, in the absence of any root growth. Apparently the induction of leaves to tuberize is affected principally by air rather than soil temperature, but expression of the signal to tuberize can be blocked by high soil temperature.