Browsing by Author "Rhizopoulou, Sophia"

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Open Access
Energy content, storage substances, and construction and maintenance costs of Mediterranean deciduous leaves
(1989) Diamantoglou, Stergos; Rhizopoulou, Sophia; Kull, Ulrich
At monthly intervals water content, crude fibre, total and protein nitrogen, sugars, starch, total lipids, ash content and calorific total energy were measured throughout the lifespan of the leaves of the deciduous mediterranean shrubs Pistacia terebinthus L. and Cotinus coggygria Scop. From these data the construction costs and maintenance costs, as well as the construction costs of non-storage compounds and energy expenditure values were calculated. The latter values were also calculated for the evergreen stemmed shrub Ephedra distachya for reasons of comparison with an evergreen mediterranean species. The water status in the deciduous leaves is stable for a long time during the drought period until the beginning of senescence in August/September. In Cotinus an early and considerable increase of storage compounds is found, whilst in Pistacia terebinthus the accumulation is more uniform until August. The N-content is rather low compared with other deciduous leaves, the calorific energy is in the lower range of the values reported for similar species. The construction costs of the leaves of both deciduous species are significantly lower than those calculated by Williams et al. (1987) for two drought deciduous chaparral species but are in agreement with the data reported by other authors on deciduous leaves. Contrary to the findings of Williams et al. they are lower than those of evergreen species; this is also true when the construction cost of the non-storage compounds alone is considered. The values found for Ephedra are similar to the maintenance costs do not show a significant variation in the deciduous leaves. They are higher than those known for evergreen leaves but somewhat lower than the values calculated for deciduous chaparral leaves.
Open Access
Seasonal trends in energy content and storage substances in the mediterranean shrub Ephedra
(1989) Diamantoglou, Stergos; Rhizopoulou, Sophia; Herbig, Astrid; Kull, Ulrich
Green branches of a shrub of Ephedra distachya L., growing in Athens, Greece, were investigated. The crude fibre content rises during the late growth period, levels off during winter, then declines as new shoots emerge in spring. The content of soluble sugars and of starch is high during winter, but rather low during the dry season. The content of total lipids rises during winter, especially during the late growth period until June and declines during the drought period. During the winter months in the total saponifiable lipids the percentage of linoleic and linolenic acids is high; however, during the growth and the drought period the content of palmitic acid is rather high. The contents of total nitrogen and protein nitrogen decrease in late spring and remain low until the end of the summer drought. Thereafter, both values rise markedly. Stored energy is lowest at the end of the summer drought period. The ashfree calorific values vary little throughout the year (but the difference is significant) : the highest value is obtained in November (19782 J/g), the lowest in May (19298 J/g). From our data, the tissue.construction cost was estimated to be 1.41-1.47 g glucose/g dry weigth. Ephedra distachya is suited to the mediterranean climate, as seen by its ability to adjust to climatic changes during the year while undergoing periods of growth and quiescence. The accumulation of sugar during the winter months suggests that Ephedra is also capable of growing under cold-stress conditions.