Cuticular waxes of the holm (Quercus ilex l. subsp. ballota (desf.) samp.) and cork (Q. suber l.) oaks
✍ Scribed by C. M. C. Martins; S. M. M. Mesquita; W. L. C. Vaz
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 58 KB
- Volume
- 10
- Category
- Article
- ISSN
- 0958-0344
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✦ Synopsis
The epicuticular leaf waxes of young leaves of the Holm oak (Quercus ilex L. ssp. ballota (Desf.) Samp.) and the cork oak (Q suber L.) were extracted in chloroform and separated into their constituent wax classes by preparative thin layer and high pressure liquid chromatography. The wax coverage was about 125 mg/cm 2 in Q. suber and about 71 mg/cm 2 in Q. ilex. The main classes encountered (by weight) were odd chain nalkanes (9% in Q. ilex, and 4-27% in Q. suber) and even chain amphiphilic compounds. The major classes of amphiphilic compounds were n-alkan-1-ols (20-27% in Q. ilex, and 18-50% in Q. suber), n-alkanals (3% in Q. ilex, and up to 25% in Q. suber), n-alkanoic acids (11-12% in Q. ilex, and 5% in Q. suber) and n-alkyl esters (50-56% in Q. ilex, and 25-45% in Q. suber). The major components of each class, identified by gas chromatography coupled to mass spectrometry were C 29 for the n-alkanes (54-58% in Q. ilex, and 47-57% in Q. suber), C 24 for the n-alkan-1-ols (78-87% in Q. ilex, and 77-93% in Q. suber), C 30 for the n-alkanals (up to 57% in Q. ilex, and up to 77% in Q. suber), C 22 and C 24 for the n-alkanoic acids in Q. ilex (39-62%) and C 30 in Q. suber (49%). The n-alkyl esters were composed mainly from C 22 and C 24 n-alkanoic acids ($38%) and n-alkan-1-ols (43-54%) in Q. ilex, whereas in Q. suber these esters were composed mainly from C 22 and C 24 n-alkanoic acids (44-52%) and C 20 and C 22 n-alkan-1-ols (32-66%). In addition to the above compounds, trace amounts (`5%) of C 28 and C 30 n-alkenes and the triterpenone, friedelin, were encountered in Q. suber and both plant waxes contained small amounts of the triterpenols aand b-amyrin (5-9% of the total alkanol content). The variability observed in the chemical composition of the leaf waxes were attributable to seasonal causes and/or leaf age.