6 benzylaminopurine 6 ba

The endogenous level of cytokinin (CTK) was quantified via high-performance liquid chromatography-mass spectrometry (HPLC-MS), according to previously described methods [13 (link)]. The compound 6-benzylaminopurine (6-BA) was obtained from Sigma-Aldrich and used as an internal standard. Abscisic acid (ABA) and indole acetic acid (IAA) concentrations were measured via an enzyme-linked immunosorbent assay (ELISA), using the protocols described by Teng et al. (2006) and Chen et al. (2009), respectively [41 (link), 42 (link)].

Seeds of Cherry belle with uniform size and plumpness were put into a 9 cm diameter petri dish lined with three pieces of filter paper and wetted with 4 ml deionized water. Three days after imbibition, the seeds were treated with deionized water or solutions including 100 μM abscisic acid (ABA, Sigma A1049), 100 μM 6-Benzylaminopurine (6-BA, Sigma B3274), 100 μM Gibberellic acid (GA₃, Sigma G7645), 50 μM alpha-Naphthaleneacetic acid (NAA, Sigma N0640), and 50 μM Ethephon (Sigma 45473). At least 300 seeds were used for each treatment. Root samples were collected 12 and 24 h after treatment, immediately frozen in liquid nitrogen, and stored at −80 °C for further use.

Suspension cells of Citrullus lanatus were generated from tender leaves and cultivated in liquid medium containing 4.43 g l⁻¹ Murashige & Skoog (MS) Basal Medium, Vitamins (PhytoTechnology Laboratories^TM, United States), 30 g l⁻¹ sucrose (Sangon, Shanghai, China), 1 mg l⁻¹ 6-Benzylaminopurine (6-BA) (Sigma, Shanghai, China), and 0.2 mg l⁻¹ 1-Naphthaleneacetic acid (NAA) (Sigma, Shanghai, China), pH 5.85. The suspension cells were incubated at 25°C in darkness on an orbital shaker (Kuhner Shaker, ISF4-X, Switzerland) at 150 rpm. The cells were subcultivated every 7 days by inoculating 5 ml of stationary cells into 15 ml of fresh medium in 50 ml Erlenmeyer flasks.