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Photosynthetic photon flux density, carbon dioxide concentration, and vapor pressure deficit effects on photosynthesis in cacao seedlings

Permanent URL:
http://handle.nal.usda.gov/10113/35243
Abstract:
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.
Author(s):
Baligar, V.C. , Bunce, J.A. , Machado, R.C.R. , Elson, M.K.
Subject(s):
Theobroma cacao , seedlings , carbon dioxide , photosynthesis , stomatal conductance , transpiration
Format:
p. 216-221.
Note:
Includes references
Source:
Photosynthetica 2008 June, v. 46, no. 2
Language:
English
Publisher:
Dordrecht : Springer Netherlands
Year:
2008
Collection:
Journal Articles, USDA Authors, Peer-Reviewed
File:
Download [PDF File]
Rights:
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.