Fig. 4.

C24×Ler hybrid seedlings grown under a photon density of 120 µmol m⁻² s⁻¹ (L₁₂₀) or 240 µmol m⁻² s⁻¹ (L₂₄₀) under short (8 h) or long (16 h) photoperiods. Arabidopsis seedlings were grown under 120 µmol m⁻² s⁻¹ for 10 DAS before half of the seedlings were transferred into 240 µmol photons m⁻² s⁻¹. The 18 DAS 240 µmol photons m⁻² s⁻¹-grown plants were assessed for heterosis in vegetative biomass and compared with the 120 µmol photons m⁻² s⁻¹-grown seedlings. (A) The images of the 35 DAS and 21 DAS C24×Ler grown under 8 h and 16 h photoperiods, respectively. (B and C) Measurements of rosette biomass. Data presented are the average and SE of n>15 from 2–3 experiments. Asterisks indicate that the hybrids were significantly different from the average levels of the parents (red dashed lines) (ANOVA, *P<0.05, **P<0.01, ***P<0.001). (D) Heterosis levels of hybrids presented as a percentage increase from the average levels of the parents. Statistical comparisons were carried out between and within hybrids in different light conditions. The asterisks indicate a significant difference from the control light under the same photoperiod (ANOVA, P<0.05).