Developmental Stage Influences Plant Response to Benzyladenine

A study was conducted to determine the effects of developmental stage (DS) on plant response to benzyladenine (BA), a synthetic cytokinin that promotes lateral shoot development. Beginning in March, April, or June 2003, three applications of 1750 or 3500 ppm BA were applied at 7-day intervals to ‘Conor’ (Eleanor Taber™) Indian hawthorn (Rhaphiolepis Lindl.) at three stages of increased shoot development (DS 1–3). At 30 and 60 days after last treatment (DALT), new shoot counts were highest on DS 2 plants, and new shoot counts increased with increasing BA rate. Plants treated at DS 1 and DS 2 incurred foliar injury, but not those treated at DS 3. A second experiment with ‘Nigra’ inkberry holly (Ilex glabra L.), ‘Harbour Dwarf’ nandina (Nandina domestica Thunb.), and ‘Conia’ (Olivia™) Indian hawthorn determined how plant DS affected severity of injury following BA application. Extensive foliar injury to ‘Nigra’ inkberry holly occurred when BA was applied to actively growing, immature foliage, but not when applied to mature foliage. Olivia™ Indian hawthorn showed moderate injury following BA treatment of plants with the most immature foliage, but not when plants were treated at more advanced stages of development. ‘Harbour Dwarf’ nandina foliage was unaffected by BA treatment regardless of DS.