Mesophyll conductance constrains photosynthesis in three common sclerophyllous species in Central Chile
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Background: Quillaja saponaria Mol., Cryptocarya alba Mol. Looser, and Lithraea caustica Molina Hook et Arn., are common sclerophyllous species in Mediterranean Central Chile. Mesophyll conductance, gm, may strongly limit photosynthesis in these semiarid environments. Results: Simultaneous measurements of gas exchange and chlorophyll fluorescence were carried out in 45 nursery plants from these species to determine diffusional and biochemical limitations to photosynthesis. Values of stomatal conductance, gs, were greater than those of mesophyll conductance, gm, while their ratio (gm/gs) was not influenced by species being on average 0.47. Relative limitations posed by mesophyll conductance to photosynthesis, Lm, (0.40 ± 0.02) were high compared to those imposed by stomata, Ls (0.07 ± 0.01). The average CO2 concentration in the intercellular air spaces (Ci) was 32 μmol mol−1 lower than in the atmosphere (Ca), while the average CO2 concentration in the chloroplasts (Cc) was 131 μmol mol−1 lower than Ci independent of species. Maximal rates of Rubisco carboxylation, Vcmax, and maximal electron transport rates driving regeneration of RuBP, Jmax, ranged from 13 to 66 μmol CO2 m−2 s−1 and from 33 to 148 μmol electrons m−2 s−1, respectively, and compare well to averages for C3 plants. Conclusions: Photosynthetic performance was in the series: Q. saponaria > C. alba ≥ L. caustica, which can be attributed first to mesophyll conductance limitations, probably mediated by leaf anatomical traits and then to species specific foliage N partitioning strategies.
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During this work the corresponding author was supported by the National Science and Technology Commission (CONICYT) through the project FONDECYT 1090259 “Disturbance mediated water and nutrient stresses regulate carbon assimilation and allocation in sclerophyll ecosystems in Central Chile: A process-based approach”. We thank Corporación Nacional Forestal for their support to carry out FONDECYT 1090259, and for providing accommodation and technical advice within the National Reserve “Roblería de los Cobres de Loncha”. We also thank Mrs. Cristina Sáez N. (Universidad de Chile), Mr. Roberto Cerda R. (CONAF) and Mr. Eric Campos (Universidad de Chile) for their kind advice and valuable technical skills. The experiments and measurements undertaken for this paper comply with the current laws of Chile
DOI: DOI: 10.1186/s40693-014-0008-0
Quote ItemRevista Chilena de Historia Natural 2014, 87:8