Why do the concentrations of Glycerate-3-phosphate in the chloroplast decreases after dark?

Glycerate-3-phosphate is a compound made during the calvin cycle in the leaf stroma. The calvin cycle is a light independent reaction, so continues when the light concentration decreases. To convert Glycerate-3-phosphate to Triose phosphate, ATP and NADPH+H are needed, which are created in the light dependant reactions in the thylakoid membranes of the chloroplasts. At the start, these compounds are available, so the concentration on glycerate-3-phosphate increases linearly, but as the concentrations of ATP and NADPH+H decrease, the rate of Glycerate-3-phosphate production decreases. This is because there is not enough Triose phosphate to regenerate the Ribulose bisphosphate as it is no longer being produced, but it is used in respiration to produce glucose.