Biosynthesis of Volatiles in Brown Boronia Flowers after Harvest: Effect of Harvest Time and Incubation Conditions

Brown boronia flowers (Boronia megastigma)were incubated at25 °C after harvest, increasing the concentration of a solventextracted product by up to 25% (d. wt basis) and floral volatilesby up to 300% (d. wt). Open flowers produced more volatilesduring post-harvest incubation than flower buds, whole flowersproduced more than flowers treated to simulate harvester damage,and fresh flowers produced more than frozen and thawed flowers.Flowers incubated in bags purged with air produced more extractand volatiles than those purged with nitrogen gas; ß-iononewas particularly depleted in nitrogen-purged flowers. Flowersand buds from three successive harvests (68, 82 and 90% openflowers) were incubated at several temperatures for up to 24h. The greatest increase in the concentration of floral extractoccurred in flowers harvested when 90% were open and incubatedfor 4 h at 12 °C, or 14 h at 23 °C. The largest increasein total volatiles occurred in material harvested at 82% openflowers and incubated for 25 h at 12 °C, or 13 h at 23 °C.The concentration of extract and volatiles declined after prolongedpost-harvest incubations. Brown boronia flowers produce volatilesand other components of the floral extract after harvest whenflowers with mature, intact enzyme systems are well suppliedwith oxygen, at temperatures at or below 25 °C. As flowersbecome visibly senescent, their ability to produce volatilesafter harvest declines.Copyright 1998 Annals of Botany Company Boronia megastigma(Nees); brown boronia; essential oils; floral volatiles; ß-ionone; phenology; post-harvest storage.