In all our experiments, FLM-ß highly correlated (R2 = 0.94) with flowering time over a broad vegetative range (15–30 rosette leaves) when determined at 15°C and tested in a homozygous background, regardless of the type of variant (Figure 5). Our finding that FLM-ß had a stronger effect in the control of flowering time than FLM-δ indicates that previously phrased functional models proposing that FLM-δ had an antagonistic activity to FLM-ß need to be corrected (Posé et al., 2013; Sureshkumar et al., 2016). This is further supported by the fact that our results estimate that FLM-δ levels are overall very low and that we did not identify a single FLM-δ clone in a directed sequencing approach that identified 53 FLM-ß clones. Our findings thus support more recent studies suggesting that the FLM-δ splice variant may be biologically irrelevant (Sureshkumar et al., 2016; Lutz et al., 2015). One of these studies also identified a large number of biologically irrelevant transcripts that could be identified with the primer combination used here for the detection of FLM-δ (Sureshkumar et al., 2016). Our data thus support the conclusion that none of these amplification products has a biologically important function (Sureshkumar et al., 2016).