Carbon isotope composition of phloem sap, wood and foliage of beech (Fagus sylvatica L.): effects of water availability and radiation during the growing season. - Geßler, ,A.,.; Schrempp, ,S.,.; Matzarakis, ,A.,.; Meyer, ,H.,.; Rennenberg, ,H.,.; and Adams, ,M..A.. (New Phytologist, 2001)