TIMING OF INDUCED VOLATILE EMISSIONS IN MAIZE SEEDLINGS

Maize (Zea mays L.) releases specific volatiles in response to herbivo ry by caterpillars. These volatiles are known to serve as cues for par asitic wasps to locate the herbivores. In the present study the exact time of volatile emission after simulated herbivory (mechanical damage and treatment with caterpillar regurgitant) was measured for seedling s of the cultivars ''Ioana Sweet Corn'' and ''LG11''. Odours were coll ected every 0.5 h for a total of 12 h. Typical ''green leaf odours'', (Z)-3-hexenal, (E)-2-hexenal, (Z)-hexen-1-ol, and (Z)-3-hexen-1-yl ace tate, were emitted immediately upon damage and their amounts dropped r apidly after the first collections. Several of the induced compounds w ere released within 2 h after treatment, while others (mainly sesquite rpenoids) started to be released after 4 h. The LG11 seedlings emitted several compounds (e.g. beta-myrcene, (Z)-beta-ocimene, benzyl acetat e, beta-caryophyllene, (E,E)-alpha-farnesene) that were not detected f or Ioana. (E, E)-alpha-farnesene was continuously emitted by LG11 seed lings, even by undamaged plants. Timing of the release of volatile com pounds that the two varieties had in common did not differ significant ly, with the exception of indole for which the peak production was con siderably earlier for LG11. These findings are discussed in the contex t of biosynthetic pathways and mechanisms involved in induced emission s of plant volatiles and the exploitation of the resulting odour by pa rasitoids and predators of herbivores.