In the present experiments, seeds of marigold (Tagetes patula nana 'Aton Flamed') and pansy (Viola x wittrockiana) were placed on moist filter paper. They were then primed for six days by dropping the temperature from 22 degsC to 10 degsC for two hours every 24 hours. Non-primed seeds were kept at a constant 22 degsC.
After six days, primed and non-primed seeds of both species were sown in soil in a growth chamber and allowed to germinate. The resulting plants were grown on in illuminated chambers at 22 degsC for three months before they were planted outdoors in June. At intervals thereafter, plants were dug up, dried in an oven and weighed. The time of flowering and the numbers of flower buds and open flowers was also recorded.
The research showed that plants of marigold and pansy that came from primed seeds were twice as heavy as those that came from non-primed seeds. They also flowered earlier and the marigolds, but not the pansies, were also taller. Seed priming in this way might usefully be extended to other bedding plants.
Pre-Sowing Seed Treatment With a Temperature-Drop Influences Plant Growth and Flowering in Marigold and Pansy by Sysoeva, Markovskaya, Sherudilo and Shibaeva (2010). Journal of Horticultural Science & Biotechnology 85 (3): 238-240. The authors' abstract of their manuscript can be seen in full at www.jhortscib.com
Dr Ken Cockshull is emeritus fellow at Warwick HRI