GluTR amount during the night and after a prolonged dark period. A, Western-blot analysis of GluTR1 and GluTR2 at the end of the light phase (18:00), during night (18:30–08:00), as well as following a prolonged dark period (3 d). B, Comparison of the GluTR1 protein amounts in A1ΔHBD, gbp, clps1, and Col-0.