Are leaf area index (LAI)and flowering related to oil productivity in peppermint?

Leaf area index (LAI)was calculated in flowering (FP)and flower bud removed (NFP)peppermint (Mentha x piperita L.)plants and related to essential oil productivity. The LAI was calculated using computerized image analysis, while the essential oils were distilled from leaves and flowers separately and analysed by GC-MS. Stolons and rhizomes were also measured and submitted to distillation. In general, flowering markedly influenced the plant phyllotaxis and also had an inhibitory effect on rhizome and stolon production. In terms of oil productivity, the avoidance of flowering did not change significantly the leaf characteristics, but it had an evident effect on the rhizomes and stolons. From a quantitative point of view menthol, the main compound in peppermint oil, was not affected by flowering avoidance, whereas a significant increase was observed for menthone in leaves of NFP. No significant correlation between LAI and oil productivity was found when FP and NFP were compared.