Influence of Oxygen Diffusion Rate on Sunflower Growth at Various Soil and Air Temperatures¹

Abstract

Synopsis Oxygen diffusion rates increased 1.8% per degree centigrade rise in soil temperature for a given surface oxygen concentration. When diffusion rates are low, higher soil or aerial temperatures are more detrimental to shoot growth than lower temperatures. Regardless of temperature, roots did not grow when oxygen diffusion rates were less than 20 × 10 −8 g. cm. −2 min. −1 . A higher diffusion rate was required to maintain optimum root growth under higher aerial temperatures but was affected very little by soil temperature.