Rockwool

For analysis of the leaf primordia, A. thaliana Col-0 (WT), or those carrying CYCLINB1;1(CYCB1;1)::GUS, an3-4, an3-4/pAtAN3::AN3-GFP, an3-4/pAtAN3::AN3-3xGFP, gl-s92f or gl-s92f/an3 were grown on sterile growth medium that contained half-strength Murashige and Skoog medium (MS; Wako), 1% (w/v) sucrose (Nacalai Tesque) and 0.8% (w/v) agar (Nacalai Tesque and Wako) adjusted to pH 5.8 with potassium hydroxide. Approximately 1 M PATI (TIBA and NPA, Sigma) stocks were dissolved in dimethyl sulfoxide and added to the medium to a final concentration of 10 µM. The medium composition was based on that described by Sieburth (1999) (link).
Seeds were sterilized by immersion in a solution of 2% (v/v) Plant Preservative Mixture^TM (Plant Cell Technology), 0.1% (v/v) Triton X-100 (Nacalai Tesque) and 50 mg/L MgSO₄ for 6 h or a solution of 10% (v/v) sodium hypochlorite (Nacalai Tesque) and 1% (v/v) Triton X-100 for 5 min and twice with sterile water before plating. The plates were incubated at 24°C under constant illumination.
For analyses of the floral organ primordia, A. thaliana Col-0 and an3-4/pAtAN3::AN3-1xGFP (Kawade et al., 2013 (link)) were sown on rockwool (Toyobo), grown under white fluorescent light conditions (∼40 µmol m⁻² s⁻¹) at 22-23°C and supplied with water containing 1 g/l powder Hyponex (Hyponex).

Fresh seeds of Rubiaceae ant plants were obtained from STRINGEPLANTS (Nagoya, Aichi, Japan). Seeds were sown on Jiffy-7 (Sakata Seed Corporation, Yokohama, Japan) fixed on rockwool (Toyobo) moistened with tap water. Cultivation was done at 23°C, under continuous illumination with light-emitting diode or white fluorescent light at 40-60 μmoles m^-2 s^-1 as described by Tsuge et al. (1996) (link). To examine the influence of gravity direction for the pore location determination, soon after extension of cotyledons, we changed the position of seedlings. Namely, seedlings were laid sideways by fixing the position of the Jiffy-7 base on rockwool to be tilted at a 90-degree angle (Figures 1G–I).