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Photosynthetic photon flux density, carbon dioxide concentration, and vapor pressure deficit effects on photosynthesis in cacao seedlings
Independent short-term effects of photosynthetic photon flux density (PPFD) of 50-400 μmol m⁻² s⁻¹, external CO₂ concentration (C a) of 85-850 cm³ m⁻³, and vapor pressure deficit (VPD) of 0.9-2.2 kPa on net photosynthetic rate (P N), stomatal conductance (g s), leaf internal CO₂ concentration (C i),...
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Published in: | Photosynthetica 2008-06, Vol.46 (2), p.216-221 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Independent short-term effects of photosynthetic photon flux density (PPFD) of 50-400 μmol m⁻² s⁻¹, external CO₂ concentration (C a) of 85-850 cm³ m⁻³, and vapor pressure deficit (VPD) of 0.9-2.2 kPa on net photosynthetic rate (P N), stomatal conductance (g s), leaf internal CO₂ concentration (C i), and transpiration rates (E) were investigated in three cacao genotypes. In all these genotypes, increasing PPFD from 50 to 400 μmol m⁻² s⁻¹ increased P N by about 50 %, but further increases in PPFD up to 1 500 μmol m⁻² s⁻¹ had no effect on P N. Increasing C a significantly increased P N and C i while g s and E decreased more strongly than in most trees that have been studied. In all genotypes, increasing VPD reduced P N, but the slight decrease in g s and the slight increase in C i with increasing VPD were non-significant. Increasing VPD significantly increased E and this may have caused the reduction in P N. The unusually small response of g s to VPD could limit the ability of cacao to grow where VPD is high. There were no significant differences in gas exchange characteristics (g s, C i, E) among the three cacao genotypes under any measurement conditions. |
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ISSN: | 0300-3604 1573-9058 |
DOI: | 10.1007/s11099-008-0035-7 |