Induction of compact growth in Campanula portenschlagiana plants by ethanol treatments

Reducing plant height for ornamental potted plants is an important factor. Conventionally, a compact growth is obtained through the extensive use of chemical growth retardants that can be hazardous to human health or the environment. In this study, ethanol irrigation was successfully proven to produce compact growth in the economically important ornamental plant Campanula portenschlagiana. The vegetative growth decreased when ethanol concentration was increased from 0.5% to 6%. Similarly, there was also a significant reduction in root length, while higher ethanol treatments from 4% were toxic and caused injuries. Further, higher ethanol levels led to partially leave yellowing or necrosis. An increase in osmotic potential was observed, but it was not significantly different between untreated plants and those treated under moderate ethanol concentration (0.5–2%). Considering the generative parameters, ethanol from 2% delayed flower formation and the longevity of flowers treated with the higher ethanol concentration (4–6%) is also significantly reduced. Generally, ethanol at moderate concentrations of 2% has desirable effects on vegetative growth traits, while it already affects generative growth, but without other obvious damage to the plants. Thus, it has been successfully demonstrated that ethanol watering is an alternative to other growth regulating agents or applications.