Large variation in whole‐plant water‐use efficiency among tropical tree species
2007
Cernusak, Lucas A. | Aranda, Jorge | Marshall, John D. | Winter, Klaus
• It is well known that whole‐plant water‐use efficiency (transpiration efficiency of carbon gain, TEC) varies among plant species with different photosynthetic pathways. However, less is known of such variation among tree species within the C₃ group. Here we measured the TEC of seven C₃ tropical tree species. Isotopic analyses (δ¹³C, δ¹⁸O, and δ¹⁵N) and elemental analyses (carbon and nitrogen) were undertaken to provide insight into sources of variation in TEC. • Plants were grown over several months in approx. 80% full sunlight in individual 38‐l containers in the Republic of Panama. Soil moisture content was nonlimiting. • Significant variation was observed in TEC among the C₃ tree species. Values ranged from 1.6 mmol C mol⁻¹ H₂O for teak (Tectona grandis) to 4.0 mmol C mol⁻¹ H₂O for a legume, Platymiscium pinnatum. • Variation in TEC was correlated with both leaf N concentration, a proxy for photosynthetic capacity, and oxygen‐isotope enrichment, a proxy for stomatal conductance. The TEC varied with C‐isotope discrimination within species, but the relationship broke down among species, reflecting the existence of species‐specific offsets.
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