2018 ASHS Annual Conference

Culm cuttings are an economically attractive method for propagating purple fountain grass [Pennisetum ×advena Wipff and Veldkamp (formerly known as P. setaceum Forsk. Chiov. 'Rubrum')] for quick liner production. Research objectives were to quantify the impact of propagation daily light integral (PDLI) and root-zone temperature (RZT) on rhizogenesis and culm development of single-internode purple fountain grass culm cuttings. Prior to culm cutting insertion, cuttings were treated with a basal dip rooting hormone solution containing 1000 mg∙L^–1 indole-3-butyric acid (IBA) + 500 mg∙L^–1 1-naphthaleneacetic acid (NAA). Cuttings were placed in a glass-glazed greenhouse with an air temperature of 23 °C, benches with RZT set points of 21, 23, 25, or 27 °C, and under PDLIs of 4 and 10 mol·m^–2·d^–1 (Expt. 1) or 8 and 16 mol·m^–2·d^–1 (Expt. 2). At 28 d, greater root biomass accumulation occurred under a PDLI of 10 mol·m^–2·d^–1 than 4 mol·m^–2·d^–1. For example, as PDLI increased from 4 to 10 mol·m^–2·d^–1, root dry mass increased by 105, 152, and 183% at RZTs of 21, 25, and 27 °C, respectively. In Expt. 2, RZT increasing from 21 to 23 °C resulted in 70% more root dry mass for cuttings under a PDLI of 8 mol·m^–2·d^–1 while root dry mass was similar among all RZTs under 16 mol·m^–2·d^–1. When these results are taken together, single-internode culm cuttings of purple fountain grass can be most efficiently propagated under PDLIs of 8 to 10 mol·m^–2·d^–1 with RZT set points of 23 to 25 °C for quick liner production.