The effects of far red spectral filters and plant density on the growth and development of chrysanthemums

Abstract

Potential interactions between plant density and the removal of far red (FR) light from crops of chrysanthemums ( Dendranthema grandiflorum) were examined. Chrysanthemums were grown in a greenhouse at one of four densities (40–100 plants m −2) with or without far red radiation, but with similar levels of photosynthetically active radiation (PAR). Removal of far red radiation by spectral filters led to a reduction in final height at flowering by 19%. This effect was most marked between internodes 6 and 11. However, no interaction occurred between far red filtering and plant density. Indeed, in chrysanthemum plant height did not increase with density when far red was present, as may be expected with a shade avoidance response. These results may suggest a mode of action for far red light in chrysanthemum, which differs from the classical shade avoidance response.