Title: Response of sunflower to strategies of irrigation III. Crop photosynthesis and transpiration
Abstract: The diurnal photosynthesis and transpiration of sunflower (cv. Sungold) subjected to three water regimes were measured on 29 days over one crop cycle using open-system field assimilation chambers. Two treatments were irrigated at weekly and 2-weekly intervals respectively and the third treatment was rainfed. The data define the high photosynthetic potential of the sunflower crop, which at LAI = 2.5 reached 9 g CO2 m−2 h−1 at global flux density of 800 W m−2, and its response to water shortage. Photosynthesis and transpiration were markedly restricted by low water supply but this response was dominated by the adjustment to LAI rather than to leaf conductance and photosynthetic rate. Wilting of stressed crops contributed more to the depression of their afternoon photosynthesis than did stomatal closure. A published model of canopy photosynthesis was able to describe the diurnal photosynthetic response of non-wilting crops to irradiance. Daily photosynthesis was highly correlated with intercepted radiation (5.24 g CO2 MJ−1) and with the ratio of daily transpiration to mean daily saturation vapour pressure deficit (119 mg CO2 (g H2O)−1). There was no effect of treatment upon daily transpiration/photosynthesis ratio.
Publication Year: 1985
Publication Date: 1985-01-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 47
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