Fig. 1: At low temperatures, PHYBs are essential to maintain growth.

a Height growth of WT and PHYBRNAi-12 plants in LD at 21 °C and 15 °C. Representative pictures of whole trees are shown in the right panel. Bars indicate a length of 10 cm. Pictures were taken after 70 days in LD at 21 °C and 15 °C. b Bud set scores of WT and PHYBRNAi-12 plants in LD at 21 °C and 15 °C. The right pictures show shoot apices of WT and PHYBRNAi plants after 70 days in LD at 21 °C and 15 °C. (c, d) Diurnal relative gene expression of FT2a and FT2b in leaves of WT and the PHYBRNAi-12 trees grown for eight weeks in LD at 15 °C. e, f Bud set scores of WT and the PHYB2-GFP OE6 plants in SD at 21 °C and 15 °C. Representative pictures of the shoot apices are shown in the right panel. Pictures were taken when bud set scores of WT plants reached stage 0.5 (green closed apical bud)²⁶. The dotted line in b,e,f marked bud set score 2, which indicates the stage of growth cessation²⁶. Data are presented as mean ± SEM (n = 9 for a, b; n = 3 for c, d, e, f). Following ANOVA, pairwise comparisons were performed using Fisher’s least significant difference (LSD) test without multiple testing correction at each time point. The statistically significant differences are indicated by non-matching letters in a,b (p < 0.05). Asterisks in c, d, e indicate the levels of statistical significance, *p < 0.05, **p < 0.01. No statistical differences were detected in (f). See also Supplementary Fig. 1 and Supplementary Table 1. Source data are provided as a Source Data file.