Fig. 1
The spreadability of the agrobacterial suspension and expression of reporters in the tested poplar clones. The transformations were carried out using A. tumefaciens EHA105, which was suspended in the infiltrated medium [10 mM MgCl2, 5 mM MES-KOH (pH 5.6) and 0.2 mM Acetosyringone (AS)]. a The spreadability of the agrobacterial suspension in the leaves of the tested poplar clones. Agroinfiltration was performed on leaves from leaf Plastochron index (LPI) 1 down to the last one (shown sequentially from left to right). The bacterial suspension spread well in clones P. davidiana × bolleana, P. alba var. pyramidalis, and P. trichocarpa, with the best performance observed in the leaves LPI 4 of P. davidiana × bolleana, LPI 4 of P. alba var. pyramidalis, and LPI 3 of P. trichocarpa, as indicated by the red stars. In contrast, the bacterial suspension was shown to be limited to a very small region in all the manipulated leaves in the other clones. The suspension was clearly delineated by leaf veins in leaves LPI 3 of clones P. tomentosa ‘B331’ and P. popularis ‘35–44’. Bars = 2 cm. b The GUS staining in the leaves of the tested clones. All infiltrated leaves were stained, and the representative images are shown. Bars = 2 mm. c The interior structure of the full-expanded leaves of the tested clones. Five-micrometer-thick sections were stained with TBO and observed using a Leica DM 5500 B light microscope. The clones P. davidiana × bolleana, P. alba var. pyramidalis, and P. trichocarpa showed larger intercellular air spaces inside the leaves compared to the other clones, in which the air spaces were smaller and more compartmented. The mesophyll cells were arranged randomly and loosely within the leaves in the clone P. davidiana × bolleana