Carbon isotope composition in relation to leaf gas exchange and environmental conditions in Hawaiian Metrosideros polymorpha populations

摘要: Carbon isotope composition, photosynthetic gas exchange, and nitrogen content were measured in leaves of three varieties Metrosideros polymorpha growing sites presenting a variety precipitation, temperature edaphic regimes. The eight populations studied could be divided into two groups on the basis their mean foliar δ13C values, one group consisting with values ca.-26‰ another ca.-28‰. Less negative appeared to associated reduced physiological availability soil moisture resulting from hypoxic conditions at poorly drained high elevation bog site low precipitation welldrained, leeward site. Gas exchange measurements indicated that intrinsic wateruse efficiency positively correlated. Maximum rates nearly constant while maximum stomatal conductance varied substantially individuals ranging from-29 to-24‰. In contrast patterns observed, leaf genetically determined independent characteristics. Photosynthetic nitrogenuse was over range suggesting compromise between water- N-use did not occur. population variations cohort age, caused ratio intercellular atmospheric partial pressure CO2 predicted calculated close agreement only youngest cohorts fully expanded leaves. results suitable precautions concerning measurement protocol, reliable indicators potential resource use by M. along environmental gradients.