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Foliar resorption of nutrients in selected sympatric tree species in gallery forest (Black Sea region)

Ozbucak T., Kutbay H., Kilic D., Korkmaz H., Bilgin A., Yalcin E., Apaydin Z.

Polish Journal of Ecology

2008

Vol. 56, nr 2

227-237

Gallery forests in Central Black Sea Region are dominated by Platanus orientalis L. The studies were performed in four sites (Mert River, Adalar, Kurupelit and Taflan Regions) located in V-shaped river valleys and differing with soil conditions. Nutrient concentrations were measured in green and senescent leaves in selected sympatric tree species. Foliar nutrient resorption efficiency (RE; as the ratio of the resorbed amounts of nutrient losses during the leaf senescence to its prior amount deposited in the leaves) and proficiency (RP; the level to which nutrient content per unit leaf mass, mg g[^-1], has been reduced in senescent leaves) were examined in several sympatric species. The high nitrogen resorption efficiency (N-RE) (62%) were found in Hedera helix L., while the lowest (40%) . in Salix alba L. The phosphorus resorption efficiency (P-RE) ranged between 35% (Rubus discolor Weithe and Nees) and 50% (S. alba) and that of potassium (K-RE) ranged between 49% (S. alba) and 62% (Robinia pseudoacacia L.). The different trend was observed in the values of proficiency (RP). The high nitrogen resorption proficiency (N-RP) ranged between 10 mg g[^-1] (Clematis vitalba L.) and 18 mg g[^-1] (R. discolor). The high phosphorus resorption proficiency (P-RP) was found in R. discolor (0.5 mg g[^-1]) similar to N-RP. The lowest P-RP was found in R. pseudoacacia (0.3 mg g[^-1]) like K-RP (5 mg g[^-1]). The high K-RP (10 mg g[^-1]) was found in H. helix. There is no significant difference between four study sites. Soil N, P and organic matter concentrations were significantly correlated with green-leaf N, P and K concentrations. Significant correlations were also found between K-RP and soil nutrient concentrations and soil moisture. However, no significant correlations were found among green-leaf nutrient concentrations, RE, RP and soil nutrient concentrations and moisture.

Ocena wpływu warunków in vitro na właściwości mechaniczne polimerów resorbowalnych o różnym czasie resorpcji

Chłopek J., Morawska-Chochół A., Szaraniec B., Ziąbka M., El Fray M.

Engineering of Biomaterials

2008

Vol. 11, no. 81-84

25--28

Celem pracy była ocena szybkości degradacji różnych polimerów resorbowalnych przetwarzanych metodą wtrysku oraz wpływu sztucznego środowiska biologicznego na zmianę właściwości mechanicznych (wytrzymałość, moduł Younga, odkształcalność) badanych materiałów. Na podstawie przeprowadzonej analizy, badane polimery można podzielić na dwie grupy: o krótkim czasie degradacji i towarzyszącej temu szybkiej zmianie parametrów mechanicznych (PGLA, PLDLA i blenda PLDLA+PGLA) oraz ulegające wolniejszej degradacji i stopniowej zmianie parametrów mechanicznych (GS i blenda GS+PLDLA). Rodzaj użytego płynu inkubacyjnego znacząco wpływa na zmianę parametrów mechanicznych próbek. Obserwowane zmiany właściwości mechanicznych badanych polimerów związane są z rozrywaniem łańcuchów polimerowych i rozluźnieniem struktury materiałów w wyniku degradacji hydrolitycznej.

The aim of the presented work was the analysis of the degradation rate of different resorbable polymers processed by injection moulding and estimation of the influence of in vitro conditions on the changes of their mechanical properties (strength, Young's modulus, elongation). The analysis of the results showed that two groups of tested polymers can be distinguished: the first one, revealing faster changes of mechanical properties due to short degradation time (PGLA, PLDLA and PLDLA+PGLA blend) and the second one, with longer degradation rate and gradual changes of mechanical properties (GS and GS+PLDLA blend). Changes of mechanical properties are connected with the scission of the polymer chains and loosening of the structure as a result of hydrolytic degradation. The type of incubation solution affects the rate of decrease of mechanical properties.