Biological and Ecological Chemistry Department, IACR-Rothamsted, Harpenden, Herts, AL5 2JQ, UK.
The quantity, ratios, their diurnal rhythm and correlation with foliage weight of volatile chemicals emitted by young and mature intact potato plants were determined during the 4th (morning), 8th (noon) and 14th (afternoon) hour of the photophase. The major compounds released by young and mature intact potato plants, Solanum tuberosum, during the photophase, were the sesquiterpene hydrocarbons beta-caryophyllene, (E)-beta-farnesene, (Z,Z)-alpha-farnesene, germacrene-D, beta-bisabolene and an unknown compound A. The quantity of the major volatile chemicals emitted was subject to diurnal rhythm. In young potatoes, all major compounds except unknown A, showed a steady increase during the photophase with the afternoon production significantly higher than that in the morning. In mature potatoes, all compounds, including unknown A were significantly higher during the afternoon when compared to morning. Although the variability in quantity of volatile chemicals released between individual plants was very high, the ratios were stable between the sets of replicates. The correlation of foliage weight and emission of the volatile compounds was affected by the developmental stage of the plant and the time of the day. Strongly evident in mature potato plants, and much less evident in young potatoes, during morning and afternoon, was a positive correlation between foliage weight and production of the volatile chemicals. No positive correlation between foliage weight and production of volatile chemicals was observed during noon for either age tested.