Essential oil formation during spatial leaf growth

The here proposed project is based on a new development in single trichome analysis by a direct, liquid "Solid phase microextraction" (SPME) method (Grassi et al., 2003b). Preliminary results on sage (Salvia officinalis) revealed that the essential oil modifications of single oil glands may not only depend on the age of the glands, but also on the position on the leaf where they were developed (Grassi et al., 2003b). In particular, single oil glands of the leaf margins were shown to contain both, essential oil compounds characteristic for young tissue as well as compounds characteristic for old tissue. This led to the suggestion that leaf expansion seems to play a significant role in the essential oil formation. In fact, the production of the monoterpene camphor, found to be accumulated in old tissues in our studies, is known to correlate with leaf expansion. The basic aim for this project is to modify leaf expansion, growth and shape by specific plant growth regulators (PGRs), herbicides and antibiotics and to investigate the influence of spatial parameters on terpenoid biosynthesis in sage and to a minor extent in camphor basil (Ocimum kilimandscharicum). The planned investigations will combine physiological, anatomical and molecular analyses of leaves, leaf zones and single oil glands with chemical features of essential oils, using chemometric and statistical analysis. We expect to provide a better understanding on essential oil formation and variation during ontogenesis, to locate where and when on the leaves specific essential oil changes occur. Finally, insights will be given why the plants invest in the complex process of essential oil formation by plant-herbivore investigations. Feeding experiments with Spodoptera sp. (Noctuidae, Lepidoptera) will reveal whether potential spatial variations in essential oil composition have any ecological relevance.

The here proposed project is based on a new development in single trichome analysis by a direct, liquid "Solid phase microextraction" (SPME) method (Grassi et al., 2003b). Preliminary results on sage (Salvia officinalis) revealed that the essential oil modifications of single oil glands may not only depend on the age of the glands, but also on the position on the leaf where they were developed (Grassi et al., 2003b). In particular, single oil glands of the leaf margins were shown to contain both, essential oil compounds characteristic for young tissue as well as compounds characteristic for old tissue. This led to the suggestion that leaf expansion seems to play a significant role in the essential oil formation. In fact, the production of the monoterpene camphor, found to be accumulated in old tissues in our studies, is known to correlate with leaf expansion. The basic aim for this project is to modify leaf expansion, growth and shape by specific plant growth regulators (PGRs), herbicides and antibiotics and to investigate the influence of spatial parameters on terpenoid biosynthesis in sage and to a minor extent in camphor basil (Ocimum kilimandscharicum). The planned investigations will combine physiological, anatomical and molecular analyses of leaves, leaf zones and single oil glands with chemical features of essential oils, using chemometric and statistical analysis. We expect to provide a better understanding on essential oil formation and variation during ontogenesis, to locate where and when on the leaves specific essential oil changes occur. Finally, insights will be given why the plants invest in the complex process of essential oil formation by plant-herbivore investigations. Feeding experiments with Spodoptera sp. (Noctuidae, Lepidoptera) will reveal whether potential spatial variations in essential oil composition have any ecological relevance.