15 Fakultätsübergreifend / Sonstige Einrichtung
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/16
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Item Open Access Der Stickstoffhaushalt immergrüner mediterraner Hartlaubblätter(1988) Diamantoglou, Stergos; Kull, UlrichThe seasonal variations of major nitrogenous components (total N, protein N) in sclerophyllous leaves of four mediterranean species - Ceratonia siliqua, Olea europaea var. sylvestris, Pistacia lentiscus and Quercus coccifera - were investigated throughout the whole lifetime of the leaves. The leaf-longevity of the first two species mentioned is about two yars, that of the latter two species is somewhat longer than one year. As reference values the raw fibre content and the total chlorophyll content of the leaves were also measured. The raw fibre content increase during leaf-growth, there-after it remains constant. In the leaves having a lifetime of two years, in the spring of the second year an additional increase, although weak, is observed. The chlorophyll content rises during the leaf growth, then remains unchanged for some time, but begins to decrease early. In the leaves of Ceratonia and Olea the shrinkage is recognized already in the spring of the second year. During the period of senescence, the decrease of chlorophyll a is more distinct than that of chlorophyll b. The total N content in all cases decreases during leaf-growth and then remains constant. In Ceratonia leaves it is reasonably high considering that it is an evergreen species. Rather early the N-content begins to decrease; which is intensified during the last months of the lifetime the leaves. This is due to the well-known export of N-compounds from senescent tissues. In Ceratonia leaves the N-content increases during the first winter; obviously they serve as N-storage organs. The content of protein-N in all species shows essentially the same variations as that of total N. Results of tests carried out in the months of January and August revealed that the proline content in the leaves of all species is higher during the drought period than during the cold period. Using the different reference-values, the variations of N-content during leaf longevity of the four species are discussed in connection with reflections on maintenance costs.Item Open Access Energy content, storage substances, and construction and maintenance costs of Mediterranean deciduous leaves(1989) Diamantoglou, Stergos; Rhizopoulou, Sophia; Kull, UlrichAt 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.