Conical tube

Coupons were individually placed in 15 mL conical tubes (Greiner Bio-One International GmbH, Kremsmünster, Austria) containing 2 mL of sterile PBS. The tubes were vortexed for 30 s, sonicated for 5 min (Branson 5510 Ultrasonic bath, Emerson Electric, Saint-Louis, MO, USA) and vortexed 30 s again. Aliquots of the supernatant were serially diluted, plated on TSA and incubated for 24 h at 37°C. CFU counts were performed using an automated method [image acquisition using Gel Doc XR+ and image processing using Quantity One (BioRad, Hercules, CA, USA)].

Shaker for gentle shaking during fixation.
Agilent slides (G2534-60530 or G2534-60535, with 8 or 4 rubber frames (Additional file 1) for whole plant/organ labeling;
Confocal microscope (recommended; alternatively, epifluorescent microscope);
Conical tubes (Greiner) 15 and 50 ml;
Cover glasses: 0.17 mm thick; 24 × 40 mm (CarlRoth, cat N. 1870.2); we recommend for high resolution microscopy always cover-glasses of defined thickness 0.17 mm ± 0.01 or 0.005 mm.
Incubator (37 °C);
Forceps (Carl Roth, cat. no. K341.1);
Humid chambers are prepared from 90 mm Petri dishes with wet absorbent paper inside;
Micropipettes;
Microscope slides for mounting of specimens after labeling;
Parafilm strips;
Poly-l-Lysine Coated Microscope Slides (e.g. from Polysciences, cat. no. 22247-1) or home-made slides coated with 10 % Poly-l-Lysine solution were used when immunolocalization experiments were performed on protoplasts or suspension cells;
Scalpel (Carl Roth, cat. no. 3607.1 or 3596.1);
Stereo microscope;
Vacuum pump (water-jet type or comparable) with a desiccator;
Well Suspension Culture Plate 12 or 24 well (Greiner, cat. no. 665102 or 662102).

The experiments were conducted to determine how NBs size distribution would under centrifugal force. The suspension containing NBs was transferred to a 15 ml conical tube (Greiner Bio-One, Oberösterreich, AT) and centrifuged at gravity acceleration 1000 G or 5000 G for 10 min (MX-301; TOMY, Tokyo, JP). NBs immediately after centrifugation were used for gene transfer experiments.