Ethylene insensitivity does not increase leaf area or relative growth rate in Arabidopsis, Nicotiana tabacum, and Petunia x hybrida.

The plant hormone ethylene plays a role in various growth related processes. In this detailed study of the vegetative growth of Arabidopsis, Nicotiana tabacum, and Petunia x hybrida plants, we show that ethylene insensitivity does not result in an increased total leaf area or relative growth rate (RGR) under optimal growth conditions. When grown in semiclosed containers, leaf area of ethylene-insensitive plants was larger compared to the wild type. This effect was caused by a buildup of ethylene inside these containers, which inhibited the growth of wild-type plants. Ethylene-insensitive Arabidopsis and N. tabacum plants had a lower biomass, which was mainly the result of a smaller seed mass. RGR of vegetative plants was not affected by ethylene insensitivity, but the underlying components of RGR differed; specific leaf area (leaf area per unit leaf mass) was higher, and unit leaf rate (growth rate per unit leaf area) was lower. The latter was a result of a slower rate of photosynthesis per unit leaf area in the ethylene-insensitive plants.