Inhibition of Pollen Germination by Volatile Compounds Including 2-Hexenal and 3-Hexenal

Vapors emitted from macerated tomato leaves inhibit germination of apple pollen. Compounds from the leaves were trapped on Tenax and identified by GC-MS. Authentic samples of the tomato leaf components and other volatiles were bioassayed for inhibition of germination, and the amounts of these compounds in the bioassay dish vapor phase were estimated by direct headspace analysis. The lipoxygenase-lyase-derived volatiles, (Z)-3-hexenal and (E)-2-hexenal, were important factors in the inhibition of pollen germination. Phenylpropanoid-derived compounds can also inhibit germination, but nonpolar compounds tested, such as terpene hydrocarbons, had little or no effect on apple pollen germination.