Production of ethylene by incubated litter of Pinus radiata

The inhibitory effect of vapour from incubated P. radiata D. Don litter to clover (Trifolium repens L.) hypocotyl growth was completely removed by KMnO₄ and ?195°C traps, but not affected by a cold trap at ?100°C. Plumule growth of rice (Oryza sativa L.) seedlings was stimulated by litter vapour, and this stimulation was removed by the KMnO₄ trap. A peak with the same retention time as ethylene was detected in the litter vapour by gas chromatography. The addition of C₂H₄ to vapour which had been passed through the KMnO₄ trap fully restored inhibition.