A simple and reliable ethylene gassing system for plant studies

An ethylene permeation system was tested in a study of flower abscission of Verticordia nitens (Lindley) Endl. Various concentrations of ethylene in air were generated by passing air, at a flow rate of 2 L/min, through chambers containing various lengths of polyvinyl chloride (PVC) tubing pressurised (50 kPa) with ethylene. Ethylene permeating through lengths of PVC tubing of 1.5, 15, 150, and 1500 cm (8 mm internal diameter, 1.5 mm wall thickness) gave ethylene concentrations in the outflow airstreams of 0.12, 0.99, 7.8, and 100 �L/L, respectively. Increasing the ethylene pressure in 150-cm-long tubing linearly increased the permeation of ethylene (0.07 �L/L. kPa). A log-linear abscission response of V. nitens flowers to increasing ethylene concentration was demonstrated using this system. Use of silicone tubing (8-mm internal diameter, 1.5-mm wall thickness) resulted in an ethylene flux 75 times that of the same length of PVC tubing. Higher flux through silicone tubing should allow development of ethylene permeation gassing systems suitable for use in fruit ripening and degreening rooms.