Spatial and seasonal variation in amino compounds in the xylem sap of a mistletoe (Viscum album) and its hosts (Populus spp. and Abies alba).

In a field study, the composition and concentrations of amino compounds in the xylem sap of the mistletoe, Viscum album L., and in the xylem sap of two host species, an evergreen conifer (Abies alba Mill.) and a deciduous broad-leaved tree (Populus x euramericana), were analyzed.

Seasonal and spatial variation of carbohydrates in mistletoes (Viscum album) and the xylem sap of its hosts (Populus x euamericana and Abies alba).

In the present field study we analysed the seasonal pattern of carbohydrate composition and contents in the xylem sap of Viscum album and the xylem sap of a deciduous (Populusxeuramericana) and a coniferous (Abies alba) host tree species. The results were compared with the soluble carbohydrate composition and contents of mistletoe tissues. On both hosts significant amounts of glucose, fructose, and sucrose were found in the xylem sap of Viscum throughout the seasons.

Elevated pCO affects N-metabolism of young poplar plants (Populus tremula × P. alba) differently at deficient and sufficient N-supply.

•  The effects of N-availability and elevated atmospheric CO partial pressure ( pCO ) on growth, allometry and N-metabolism of poplar plants are reported here. •  Poplar plants were grown hydroponically at deficient and sufficient N-supply under ambient and elevated pCO . The N-fluxes within the plants were estimated by comparing the fate of newly acquired N-NO in plants either severely N-limited or with sufficient N-supply.

Elevated pCO(2 )favours nitrate reduction in the roots of wild-type tobacco (Nicotiana tabacum cv. Gat.) and significantly alters N-metabolism in transformants lacking functional nitrate reductase in the roots.

The impact of elevated pCO(2 )on N-metabolism of hydroponically grown wild-type and transformed tobacco plants lacking root nitrate reduction was studied in order to elucidate the effects on (i) nitrate uptake, (ii) long-distance transport of N, (iii) nitrate reduction with emphasis on root-NR, and (iv) the allocation of N between the root and shoot. The findings were related to alterations of growth rates. At elevated pCO(2 )the wild type exhibited higher growth rates, which were accompanied by an increase of NO(3)(-)-uptake per plant, due to a higher root:shoot ratio.