Seasonal Changes in Carbohydrates, Lipids and Fatty Acids of Two Mediterranean Dimorphic Phrygana Species

Abstract

Storage patterns of soluble sugars, starch, lipids and fatty acids were investigated in leaves, stems and roots of Euphorbia acanthothamnos and Phlomis fruticosa throughout a year. Winter leaves of both species contained higher amounts of lipids than summer leaves. Leaf soluble sugar content showed two peaks (winter and summer) in P. fruticosa and a winter peak in E. acanthothamnos. Starch was mainly accumulated in young expanding winter- and summer-leaves and depleted twice over the year, during the cold winter and the drought summer, respectively. Considering stems and roots, storage substances exhibited identical fluctuations, i.e. the maximum values of lipids being recorded during winter and those of starch during spring. The molar quotient (MQ) of polyunsaturated to saturated fatty acids was low, mainly due to the high percentage of palmitic acid in all tissues of both examined species. Nevertheless, roots exhibited a different fatty acid composition than the above ground parts of the plants. The energy content of storage substances (ECS) was mainly contributed by lipids and the minimum values in both species were recorded during drought. On the basis of seasonal variation of ECS, dimorphic phrygana can be situated between mediterranean evergreen sclerophylls and central european evergreen conifers. It was presumed that in the case of dimorphic phrygana, summer seems to be a dormant period, whereas winter the investive period.