Pennsylvania Flower Growers #222
Garner and Allard first reported the response of plants to the length of day in 1920. They referred to this response as "photoperiodism." Until 1955, the carnation was considered to be indifferent to length of day for flower bud formation. Research re ports then began to note the elongation of internodes on carnation plants which grew under long days in contrast to plants grown under short days. Short days were also found to produce more nodes than long days. This was followed by the discovery that long days hastened flower bud initiation and short days delayed the process. Finally, it was discovered that plants from mother block plants grown under a short-day treatment yielded more flowers per square foot than similar plants grown under long days. Short-day treatment of the mother block increased the number of nodes on the cuttings. Quality of Light Quality of light refers to the color, which varies with wave length. Plant growth (photosynthesis) is most affected by the red and blue1 bands. Day length response (photoperiodism) is most affected by the red and far red wave lengths.
Keywords: Short-day treatment Lighting Equipment Flower initiation internode elongation Quality