The relationship between the activation state of sucrose-phosphate synthase and the rate of CO2 assimilation in spinach leaves.

The relationship between the gas-exchange characteristics of spinach (Spinacia oleracea L.) leaves and the activation state of sucrose-phosphate synthase was examined at different intercellular partial pressures of CO2 at two different photon flux densities. There was a strong positive correlation between the activation state of sucrose-phosphate synthase and the assimilation rate. The relationship was the same at both photon flux densities, indicating that the activation state of the enzyme is determined by a product of carbon assimilation, rather than directly by light.