CHEMICAL-CONSTITUENTS FROM SHOOTS OF HORDEUM-VULGARE INFESTED BY THE APHID SCHIZAPHIS-GRAMINUM

Stress, pathogens or insects induce profound changes in the expression of the chemical constituents of plants. Some of these changes could b e adaptations to the new conditions or the expression of new defensive characteristics. The purpose of this paper was to analyze the effect of aphid infestation on the composition of endogenous compound, in bar ley leaves. Leaf waxes were obtained by washing with dichloromethane a nd remaining compounds were extracted with ethyl acetate and ethanol f rom homogenized leaves. The identification of compounds was done by co mbined capillary gas chromatography and mass spectrometry. Epicuticula r compounds detected in barley after 6 days of aphid infestation were as follows (%): (1) 1-docosene (1.98), (2) 1-octadecene (2.07), (3) ph ytol (0.81). Epicuticular compounds in non-infested plants were (4) is ophytol (0.83), (5) N-cyclohexyl-cyclohexanamine, (0.11) (6) 5-pentade cyl-1,3-benzenediol (2.10). In ethyl acetate extracts from infested pl ants the main compounds were: (1) (2.02), (7) 2,5-diethylpyrazine (0.6 1), (8) (5E)-eicosene (1.61), (9) (3E)-eicosene (1.93), (10) (9E)-eico sene (1.80). In non-infested plants the only detected compounds were ( 1) (1.02), (6) (1.91), and (7) (0.43). In methanol extracts from infes ted plants the following compounds were identified: (6) (2.15), (7) (0 .21), (11) 2,2,6.6 tetramethyl-piperidine (0.12), (12) indole (1.01), (13) heptadecane (0.10), (14) methyl-beta-D-glucopyranoside (0.21), (1 5) 2,5- dihydroxybenzaldehyde (0.27) and (16) N-phenyl-2-naphthalenami ne (0.29). In polar extracts from non-infested plants the most abundan t compounds were (4) (1.40), (7) (0.18), (17) (9Z,12Z,15Z)-octadecatri enoic methyl ester (1.01), (18) (9Z,15Z)-octadienoic methyl ester (2.0 1), and (19) hexadecanoic methyl eater (1.93). Compounds 4, 5 and 7-19 are described for the first time in Hordeum vulgare.