Ethylene losses and release were compared in four container- seal systems for in vitro cultures: Erlenmeyer flasks sealed with silicone, caoutchouc or styrene butadiene stoppers and glass bottles with screw caps supplied with caoutchouc septa. The last systems Proved to be the most suitable (i. e. minimum ethylene loss and release) to determine ethylene accumulation during axillary budding of lavandin (Lavandula officinalis Chaix × Lavandula latifolia Villars cv. Grosso). Gelling agents (agar and Gelrite) also discharges ethylene and agar was identified as the main abiotic source. Mathematical elaboration of experimental data was then performed to estimate biological ethylene production.