Articles
MODELING TEMPERATURE EFFECTS ON CROP PHOTOSYNTHESIS AT HIGH RADIATION IN A SOLAR GREENHOUSE
Article number
593_17
Pages
137 – 144
Language
English
Abstract
The climate inside a solar greenhouse (a high-tech greenhouse essentially heated by solar energy and provided with facilities for seasonal energy storage) is more dependent on outside conditions than in ordinary greenhouses.
To optimise ventilation, one has to take into account that optimum temperature for canopy photosynthesis rises with increasing concentration of atmospheric CO2. To predict canopy photosynthesis and to relate dry weight production to temperature control, a reliable model is needed.
Models of canopy photosynthesis have not yet been validated at the extreme climate situations that may be expected in a solar greenhouse in summer (high irradiation, temperature and humidity). Three versions of increasing complexity of leaf photosynthesis simulation models, M1, M2, and M2+ were evaluated in a canopy photosynthesis model under such conditions.
The reference (SUCROS related) model, M1, has been extensively validated for a tomato crop under normal greenhouse conditions.
M2 is an extension of M1 with a more biochemical description of the underlying processes.
M2+ is an extension of M2, including a sub-model of stomatal resistance.
In a crop model, the three sub-models were compared under fixed conditions and with observed climate data.
There were substantial differences between the three models, especially at high temperatures and high radiation, irrespective of the CO2 level.
The biochemical model, M2, performed somewhat differently than M1 . But, the strongest discrepancies were observed with model M2+ due to the much higher predicted stomatal resistance compared to the values adopted in M1 and M2. The results demonstrate that it is necessary to investigate the performance of greenhouse crop models under a wider range of conditions when they are to be applied in a solar greenhouse.
To optimise ventilation, one has to take into account that optimum temperature for canopy photosynthesis rises with increasing concentration of atmospheric CO2. To predict canopy photosynthesis and to relate dry weight production to temperature control, a reliable model is needed.
Models of canopy photosynthesis have not yet been validated at the extreme climate situations that may be expected in a solar greenhouse in summer (high irradiation, temperature and humidity). Three versions of increasing complexity of leaf photosynthesis simulation models, M1, M2, and M2+ were evaluated in a canopy photosynthesis model under such conditions.
The reference (SUCROS related) model, M1, has been extensively validated for a tomato crop under normal greenhouse conditions.
M2 is an extension of M1 with a more biochemical description of the underlying processes.
M2+ is an extension of M2, including a sub-model of stomatal resistance.
In a crop model, the three sub-models were compared under fixed conditions and with observed climate data.
There were substantial differences between the three models, especially at high temperatures and high radiation, irrespective of the CO2 level.
The biochemical model, M2, performed somewhat differently than M1 . But, the strongest discrepancies were observed with model M2+ due to the much higher predicted stomatal resistance compared to the values adopted in M1 and M2. The results demonstrate that it is necessary to investigate the performance of greenhouse crop models under a wider range of conditions when they are to be applied in a solar greenhouse.
Authors
O. Körner, H. Challa, R.J.C. van Ooteghem
Keywords
CO2, humidity, simulation, stomatal resistance, tomato
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