The role of dead standing biomass of Calamagrostis epigejos in nutrient turnover during spontaneous succession.

Here we explore the idea that keeping dead standing (marcescent) biomass plants can reduce its nutrient (N, P) content. Later after biomass falling to ground this may result in substantial changes in nutrient turnover with consequences for plant competitive interactions. To explore the effects standing dead biomass we used Calamagrostis epigejos as a model species. It is a common expansive grass, which after senescence retain a large proportion of the plant remains as dead standing biomass. We determined the biomass, N and P concentrations of living biomass, standing dead biomass, and lying dead biomass at young and old successional sites on the post-mining heap near Sokolov. Further, we analyzed nutrient budget in dead biomass during decomposition and we compared it with nutrient budget in decomposing cellulose. Concentrations of N and P in living biomass were highest in April and decreased during season. Lying dead biomass had a higher N concentration than N concentration contained in standing dead biomass. A litterbag experiment revealed that N was released from lying dead biomass but accumulated in standing dead biomass during decomposition. Similarly the N was accumulated in decomposing cellulose. This accumulation was highest in sites with low decomposition rate. In late summer and autumn lying biomass was derived from senescence plants, came to soil and N was released during decomposition potentially usable for C. epigejos. Standing dead biomass turned to lying biomass during winter and spring and then during its decomposition N was immobilized from soil. This mechanism could reduce availability of N for other plants and increase competitive advantage of C. epigejos regrowing from belowground organs during spring.

Some cytostatic and pharmacological properties of 2,3-dihydro-1,3-6H-oxazine-2,6-dione ("3-oxauracil").

Cytostatic effects and some pharmacological properties of a new metabolic inhibitor "3-oxauracil" were studied. The cancerostatic effect was examined on 7 experimental tumors in mice and on two types of tumors in rats. After the i. p. application of 20 mg/kg, there was both a statistically significant decrease of tumor weight and increase of animals' survival time in NK lymphoma of mice. Significant changes in one of both parameters followed occured in all experimental tumors after the i. p. application but only in the Krebs ascitic carcinoma after the oral application of "3-oxauracil". The acute toxicity of the substance in water was 322 mg/kg i. p. and 850 mg/kg p. o. The ethanol solutions were more toxic. The distribution of the 3H- and 14C-labeled substance was followed up in blood, urine, liver, brain and kidney. After the p. o. application, the radioactivity peak was reached after 2 hr in blood and high radioactivity levels were found in kidney followed by brain and liver. 96 hr after the drug was applicated perorally, only 60% of radioactivity was found in urine.