Genotypic variation in physiological and growth responses of Populus tremuloides to elevated atmospheric CO2 concentration.
Physiological and biomass responses of six genotypes of Populus tremuloides Michx., grown in ambient t (357 micromol mol(-1)) or twice ambient (707 micromol mol(-1)) CO2 concentration ([CO2]) and in low-N or high-N soils, were studied in 1995 and 1996 in northern Lower Michigan, USA. There was a significant CO2 x genotype interaction in photosynthetic responses. Net CO2 assimilation (A) was significantly enhanced by elevated [CO2] for five genotypes in high-N soil and for four genotypes in low-N soil. Enhancement of A by elevated [CO2] ranged from 14 to 68%. Genotypes also differed in their biomass responses to elevated [CO2], but biomass responses were poorly correlated with A responses. There was a correlation between magnitude of A enhancement by elevated [CO2] and stomatal sensitivity to CO2. Genotypes with low stomatal sensitivity to CO2 had a significantly higher A at elevated [CO2] than at ambient [CO2], but elevated [CO2] did not affect the ratio of intercellular [CO2] to leaf surface [CO2]. Stomatal conductance and A of different genotypes responded differentially to recovery from drought stress. Photosynthetic quantum yield and light compensation point were unaffected by elevated [CO2]. We conclude that P. tremuloides genotypes will respond differentially to rising atmospheric [CO2], with the degree of response dependent on other abiotic factors, such as soil N and water availability. The observed genotypic variation in growth could result in altered genotypic representation within natural populations and could affect the composition and structure of plant communities in a higher [CO2] environment in the future.
Wang
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Environmental Science Graduate Program, Ohio State University, Columbus 43210, USA.
Curtis
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PS
Pregitzer
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KS
Zak
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DR
D018533:Biomass; D002245:Carbon Dioxide / Q000502:physiology; D014644:Genetic Variation / Q000502:physiology; D005838:Genotype; D010788:Photosynthesis / Q000502:physiology; D018515:Plant Leaves / Q000502:physiology; D014197:Trees / Q000235:genetics / Q000254:growth & development / Q000502:physiology*
D002245:Carbon Dioxide