CuSO4 filters influence flowering of Chrysanthemum cv. Spears

'Spears' chrysanthemums (Dendranthema x grandiflorum [Ramat.] Kitamura) wer e grown under solar filters filled with CuSO4 in solution which absorbs FR, or water, which does not absorb FR, and were exposed to marginally long na tural photoperiods, artificially long photoperiods, or artificially short p hotoperiods. Internode length and plant height were reduced under CuSO4 fil ters compared to plants grown under water filters, regardless of photoperio d. Plants grown under water- or CuSO4-filled filters that received artifici al short days flowered 7 days ahead of the plants grown in natural, margina lly long photoperiods under CuSO4 filters and 17 days ahead of the plants g rown under water filters and receiving natural, marginally long photoperiod s. The number of nodes was the same for the plants grown in short and margi nally long days under CuSO4 filters and in shea days under water filters, i ndicating that flower induction occurred simultaneously in these treatments . Development of additional nodes on plants under water-filled filters and receiving natural long-days indicated that floral induction was delayed. A cool white fluorescent light night break prevented or delayed flowering of plants grown under water- and CuSO4-filled filters during natural short day s. The results demonstrate that standard practices of photoperiodic control can be used to time chrysanthemums 'Spears' grown under CuSO4 filters for pot mum production. (C) 1999 Elsevier Science B.V. ALI rights reserved.