CONTROL OF THE SHOOT ELONGATION IN BEDDING PLANTS USING EXTREME SHORT DAY TREATMENTS
Plant growth and shoot elongation in ornamental crops is often controlled using chemical growth retardants. Such chemicals are undesirable from an environmental and occupational health perspective, so alternative methods for controlling growth are required. This study examined control of shoot elongation by photoperiod manipulation using blackout screens. The common bedding plant species Calibrachoa, Pelargonium, Petunia and Scaevola were grown using light regimes incorporating an extreme short-day period (8 h photoperiod day-1). Shoot growth was recorded weekly and plant height, width and flower development were measured at the end of experiment. A period of short-day treatment at the end of crop growth suppressed shoot elongation significantly compared with plants grown under a natural photoperiod. High-quality, fully marketable plants were obtained with no use of chemical growth retardants. However, for the long-day species there was a reduction in the number of flowers and a delay of flowering due to the short-day treatments. Short photoperiod treatment proved effective as a strategy for reducing shoot elongation in bedding plants, and also as a method for timing the crop. A positive side-effect was the reduction in greenhouse heat requirement when the blackout screens were closed.
Schüssler , H.K. and Bergstrand , K.-J. 2012. CONTROL OF THE SHOOT ELONGATION IN BEDDING PLANTS USING EXTREME SHORT DAY TREATMENTS. Acta Hort. (ISHS) 956:409-415
Calibrachoa, growth control, Pelargonium, Petunia, photoperiod, Scaevola, timing