Hydraulic conductance and stomatal sensitivity to changes of leaf water status in six deciduous tree species

The relationship between shoot hydraulic conductance (L) and stomatal sensi tivity to changes in leaf water status was studied in the saplings of six d eciduous tree species. L increased significantly in sequence: Acer platanoi des < Tilia cordata < Padus avium = Quercus robur < Salix caprea = Populus tremula. L was higher in the trees grown in soil with a higher nitrogen con tent and lower in the trees grown under mild water stress or kept in darkne ss for several days. L was higher in July than in September in all the spec ies. L correlated positively with maximum photosynthesis, stomatal conducta nce and stomatal sensitivity to an increase in leaf water potential, but ne gatively with stomatal sensitivity to a decrease in leaf water potential. T he correlations between L and any other parameter were approximated by thre e different curves: data for water-stressed plants fit to the first, data f or plants kept in darkness fit to the second and all the other data fit to the third curve. The reasons of the differences of shoot hydraulic conducta nce in the different experimental sets and the mechanisms which may cause t he correlation between L and the other characteristics are discussed.