ISHS Acta Horticulturae 416: IV International Symposium on Computer Modelling in Fruit Research and Orchard Management
SOURCE:SINK EFFECTS ON PHOTOSYNTHESIS: MODELS AT DIFFERENT SPATIAL SCALES |
| Authors: | J.G. Buwalda, G.J. Piller |
| Abstract:
Different information can be represented in models of photosynthesis (A) at different spatial scales. Models of leaf A can be applied to examine spatial and temporal heterogeneity of carbon acquisition. Responses of leaf A to incident radiation (PAR) have been described using asymptotic exponential equations. Such descriptions can be spatially integrated, to describe canopy A. Such whole canopy models can be used to describe temporal trends of carbon acquisition for the whole plant. We illustrate such models, using kiwifruit as an example. The mechanistic basis of source: sink effects on photosynthesis has been examined further, using measured responses of leaf A to sub-stomatal CO2 (Ci). Mathematical descriptions of such responses have shown that source: sink balance affects particularly the ratio of stomatal and mesophyll resistances to CO2 diffusion (lg). At the time when fruit growth is most rapid (soon after pollination), leaf A and stomatal conductances are relatively high, but an apparently faster rate of CO2 depletion was associated with a transient increase in lg. Leaves on vegetative shoots bearing no fruit did not show an elevation in this ratio. | |
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