Diurnal changes in leaf gas exchange and validation of a mathematical model for coffee (<Emphasis Type="Italic">Coffea arabica</Emphasis> L.) canopy photosynthesis |
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Authors: | L?F?Gomez J?C?Lopez Email author" target="_blank">N?M?RianoEmail author Y?Lopez E?C?Montoya |
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Institution: | (1) Federacion Nacional de Cafeteros de Colombia, Centro Nacional de Investigaciones de Cafe, CENICAFE, Chinchina, Colombia;(2) Facultad de Ciencias Agropecuarias, Universidad Nacional de Colombia, Palmira, Colombia |
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Abstract: | Diurnal variations in net photosynthetic rate (P
N), transpiration rate (E), stomatal conductance (g
s), internal CO2 concentration (C
i), and water use efficiency (WUE) were studied on individual leaves of coffee plants to determine the effect of climatic factors
on photosynthetic capacity. P
N and E showed bimodal behaviour with the maximum values of P
N at mid-morning. At noon, under saturating photosynthetically active radiation (PAR) and high leaf temperature (T
l), P
N declined. In the afternoon (14:00), P
N slightly recovered in association with a decrease in Tl and in leaf-to-air vapour pressure deficit (VPD). Reductions in E during the morning were associated with decreases in g
s. Higher WUE in the morning was related to higher P
N and lower E. The reverse occurred in the afternoon. Goudriaan's simulation model, adapted for coffee canopy photosynthesis, was tested
at the level of whole plant (P
pl). Three methods were used: (a) Whole plant net photosynthesis (P
pl) under semi-controlled conditions in a chamber. (b) P
pl estimation following Goudriaan's method (Gaussian integration) of instantaneous P
N in single leaves at three canopy depths and at three different hours assuming a photosynthesis unimodal behaviour. (c) P
pl using Goudriaan's method but at five different hours according to the bimodal behaviour reported above. Results of P
pl estimates using Goudriaan's model adapted for coffee canopy confirm the observed P
pl bimodal behaviour with high fitness degree of the measured whole plant photosynthesis. The high fitness found among observed
and simulated data indicates that the modified model may be used as a subroutine for the general simulation model of coffee
crop growth. |
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Keywords: | Goudriaan's model leaf gas exchange net photosynthetic rate whole plant photosynthesis |
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