The effect of spectral filters and nitrogen dose on the growth of chrysanthemum (Chrysanthemum morifolium Ramat., cv. Snowdon)

Abstract

SummaryThis study has searched for interactions between the effects of nitrogen dose, applied at one of four levels, 0.316, 1.0, 3.16 and 10 mM, and four different spectral filters on the growth and development of chrysanthemums. The filters used included two controls with different overall transmissions to photosynthetically active radiation (PAR) and two further materials, which selectively filtered either red or far-red light, but with PAR transmission similar to one of the controls. Increasing the nitrogen dose to a maximum of 10 mM from the lowest level led to a four-fold increase in plant dry mass, and a near two-fold increase in plant height. The FR absorbing spectral filters produced significantly shorter plants than both controls (by ca. 10% at final flowering) and for this variable there were no interactions with nitrogen dose. At 10 mM N, the FR-absorbing material also led to an increase in leaf area compared with the R-absorbing material (by 55% after 40.d). However, a significant interaction occurred with N dose, such that the FR-absorbing filter increased leaf area only at the highest levels of N. The results are discussed in terms of the potential use of spectral filters for the control of the growth of ornamental crops.