LEAF WAX OF LACTUCA-SATIVA AND PLANTAGO-MAJOR

Wax layers of plants are able to accumulate semivolatile organic compo unds (SOCs) from the atmosphere In this study, the composition;of the leaf cuticular waxes of lettuce (Lactuca sativa) and common plantain ( Plantago major) was determined for future studies on the role of cutic ular waxes in the uptake and bioaccumulation of SOCs. In addition, to find a suitable extraction solvent to be used in these studies, the ex traction efficiency of several solvents for the cuticular wax of the p lants was studied. Leaf wax of L. sativa consists mainly of long-chain linear alcohols and minor amounts of fatty acids, while the major com ponents of leaf wax of P. major are the free polar triterpene acids, o leanolic and ursolic acid, and the linear alkanes C27H56C33H58. The wa x composition of both species only slightly changes with leaf developm ental stage. This property makes them highly suitable as test plants i n studies on uptake of SOCs. The waxes of both plant species are readi ly extractable with chloroform, toluene and dichloromethane. A mixture of chloroform and methanol 2:1 additionally extracted internal lipids and chlorophyll and, therefore,is not suitable. The apolar solvent, n -hexane, did not extract the triterpene acids of P. major. However, th is solvent readily extracted the relatively apolar leaf wax of L. sati va. Since the extraction of SOCs (also from deeper embedded wax layers ) can only be efficient if all the components of the cuticular wax are removed, we recommend to test the extraction efficiency of the solven t for each plant species beforehand. (C) 1998 Elsevier Science Ltd. Al l rights reserved.