Ethylene is required in tobacco to successfully compete with proximate neighbours

Plants sense neighbours even before these cause a decrease in photosynthetic light availability. Light reflected by proximate neighbours signals a plant to adjust growth and development, in order to avoid suppression by neighbour plants. These phenotypic changes are known as the shade-avoidance syndrome and include enhanced shoot elongation and more upright-positioned leaves. In the present study it was shown that these shade-avoidance traits in tobacco (Nicotiana tabacum) are also induced by low concentrations of ethylene. Furthermore, it was shown that transgenic plants, insensitive to ethylene, have a delayed appearance of shade-avoidance traits. The increase in both leaf angles and stem elongation in response to neighbours are delayed in ethylene-insensitive plants. These data show that ethylene is an important component in the regulation of neighbour-induced, shade-avoidance responses. Consequently, ethylene-insensitive plants lose competition with wild-type neighbours, demonstrating that sensing of ethylene is required for a plant to successfully compete for light.