Articles
MEASUREMENT, MODELING AND SEASONAL CHANGES OF CANOPY PHOTOSYNTHESIS IN ‘NYOHO’ STRAWBERRY
Article number
439_96
Pages
575 – 582
Language
Abstract
The photosynthetic rate of a strawberry crop on ground area basis was determined by measuring the changes in CO2 concentration in commercial greenhouses, using the estimated rate of soil respiration and number of exchanges during the dark period.
To estimate the photosynthetic curves, four theoretical equations; (1) y=a+bcx, (2) y=a+b/(c+x), (3) y=a+b√x and (4) y=a+bx, were fitted to the photosynthetic responses of canopy to light at several ranges of CO2 concentration by the least square method.
When the observed light intensity was higher than 300 W m-2 and the CO2 concentration was less than 500 mL m-3, the asymptotic equation (1) was fitted better than the others and reasonable rates of saturated photosynthesis were obtained with equation (1). At higher CO2 concentrations (>1100 mL m-3), the asymptotic equations (1) and/or (2) could not be fitted, as such high values were observed only in the morning when the light intensity was less than 150 W m-2, considerably lower than the light saturation point.
At various CO2 concentrations, although the photosynthetic response to light should be estimated with the equation (1), it was possible to estimate with the equation (3), as there were few differences among the curves obtained with the equations (1), (2) or (3), when the light intensity was less than 200 W m-2. The estimated rate of canopy photosynthesis was higher in December than February or March.
This should be due to the difference in the leaf area index (LAI) of the canopy.
The estimated photosynthetic rate at 100 W m-2 was increased with the increase in the CO2 concentration up to 1000 mL m-3, and the rate was higher at 100 W m-2 and 600 mL m-3 than at 200 W m-2 and 350 mL m-3. The CO2 concentration in the strawberry greenhouses should be maintained at ca. 1000 mL m-3 with supplemental enrichment, especially under low light conditions.
To estimate the photosynthetic curves, four theoretical equations; (1) y=a+bcx, (2) y=a+b/(c+x), (3) y=a+b√x and (4) y=a+bx, were fitted to the photosynthetic responses of canopy to light at several ranges of CO2 concentration by the least square method.
When the observed light intensity was higher than 300 W m-2 and the CO2 concentration was less than 500 mL m-3, the asymptotic equation (1) was fitted better than the others and reasonable rates of saturated photosynthesis were obtained with equation (1). At higher CO2 concentrations (>1100 mL m-3), the asymptotic equations (1) and/or (2) could not be fitted, as such high values were observed only in the morning when the light intensity was less than 150 W m-2, considerably lower than the light saturation point.
At various CO2 concentrations, although the photosynthetic response to light should be estimated with the equation (1), it was possible to estimate with the equation (3), as there were few differences among the curves obtained with the equations (1), (2) or (3), when the light intensity was less than 200 W m-2. The estimated rate of canopy photosynthesis was higher in December than February or March.
This should be due to the difference in the leaf area index (LAI) of the canopy.
The estimated photosynthetic rate at 100 W m-2 was increased with the increase in the CO2 concentration up to 1000 mL m-3, and the rate was higher at 100 W m-2 and 600 mL m-3 than at 200 W m-2 and 350 mL m-3. The CO2 concentration in the strawberry greenhouses should be maintained at ca. 1000 mL m-3 with supplemental enrichment, especially under low light conditions.
Publication
Authors
Y. Yoshida, Y. Morimoto
Keywords
Fragaria x ananassa, curve fitting, soil respiration, carbon dioxide, light intensity
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