Thermal stress is one of the most common environmental challenges confronting plants.
Transgenic iaaLys plants, which contain reduced levels of free IAA, exhibit a dramatic reduction in TIHE as do auxin response and transport mutants. These data suggest that TIHE is an auxin mediated response. Furthermore, initial results indicate that growth at high temperature results in an increase in auxin-induced gene expression suggesting that thermal stress may stimulate at least some aspects of auxin response. Although the physiological relevance if this response is unknown, hypocotyl elongation may function to lower the temperature of the leaves and apical meristem by increasing the distance from the heat-absorbing soil and by allowing the plant to take better advantage of the cooling effect of moving air.