Rooting of two Boronia species as influenced by α-naphthalene acetic acid (NAA) and 2-chloroethyl phosphonic acid (CEPA)

The effect of naphthalene acetic acid (NAA) at 2000 ppm on the rooting of Boronia cymosa and Boronia muelleri cuttings was evaluated between June-September (winter) and September-December (spring) at UQ Gatton, Southern Queensland. The response to ethylene was also tested, with or without NAA. Ethephon or CEPA (2-chloroethyl phosphonic acid), an ethylene-generating compound, was applied at 250 ppm prior to NAA application. The percentage and time to rooting were recorded. The two species responded differently. NAA application resulted in earlier rooting in Boronia cymosa in winter and spring, and in Boronia muelleri in spring only. NAA increased rooting percentage in Boronia cymosa in spring but not in Boronia muelleri. Conversely, pretreatment with CEPA prior to NAA application promoted earlier rooting in Boronia muelleri, but did not increase the final percentage rooting in either species