(A) Morphology of switchgrass plants overexpressing different levels of STF at flowering. One representative from each group was shown. Bars = 10 cm for plants, 1cm for leaves. (B) Transcript abundance of STF in transgenic plants revealed by qRT-PCR. UBI::GUS-1 switchgrass plant was used as the control. Bars represent means ± SE of three technical replicates. (C) Comparison of postharvest dry weights of total above-ground biomass of three control (UBI::GUS plants) and three classes of STF overexpressors shown in (B) at maturity. Bars represent means ± SE (n = 3 independent plants for Control, Group Ⅰ, Ⅱ, and 2 plants for group Ⅲ), the asterisks indicate significant differences (*p<0.05, **p < 0.01, Student t-test). (D) Solubilized sugar yield of transgenic switchgrass plants compared to control (UBI::GUS plants) shown in (B). Bars represent means ± SE (n = 3 plants for Control, Group Ⅰ and Ⅱ, 2 plants for group Ⅲ), the asterisks indicate significant differences (*p<0.05, **p < 0.01, Student t-test). (E) Phloroglucinol-HCl staining of lignin in the internode Ⅲ of the control (UBI::GUS-1) and Group Ⅱ STF-10. Bars = 100 μm. (F) Recovery and growth establishment after shoot harvest. The STF transgenic switchgrass (Group Ⅱ STF-10) displays better recovery after cut back compared to the control (UBI::GUS-1). Plants shown were 2 weeks old after cutting. Bars = 5 cm.