BIOMASS ACCUMULATION, ALLOCATION AND LEAF MORPHOLOGY OF IMPATIENS HAWKER 'MAGNUM SALMON' CUTTINGS IS AFFECTED BY PHOTOSYNTHETIC DAILY LIGHT INTEGRAL IN PROPAGATION

Recent research has shown that increasing the photosynthetic daily light integral (DLI) during propagation of cuttings increases root growth and overall quality of rooted cuttings. Our objectives were to determine how biomass accumulation and allocation and leaf morphology of Impatiens hawker (New Guinea impatiens) cuttings were influenced by the photosynthetic DLI during root development in propagation. Cuttings of New Guinea impatiens ‘Magnum Salmon’ were inserted into propagation substrate in cell trays and placed under mist in environmental conditions for callus development (approximately 5 mol m^-2 d^-1) for 7 days. After 7 days, cuttings were placed under DLIs of 2.5, 8.5, or 15.6 mol m^-2 d^-1 for 14 days. Total, leaf, stem, and root dry mass increased for cuttings within each DLI over time, and dry mass generally increased with DLI. Dry mass partitioning was greatest into leaves for cuttings under 2.5 mol m^-2 d^-1 and roots for cuttings under 8.5 and 15.6 mol m^-2 d^-1. Total leaf area increased throughout the experiment for all cuttings, while final total leaf area was highest under 15.6 mol m^-2 d^-1. The leaf area ratio and specific leaf area increased for cuttings under 2.5 mol m^-2 d^-1, but not under higher-light treatments. These results suggest cutting morphology and physiology is plastic in response to DLI during root development.