Improvement Of Rose Seed Germination With Red Light
Published in The Rose Hybridizers Association Newsletter, Volumn 28, No. 2, Summer 1997, pages 3-4.
In 1980 Paul Jerabek wrote the following to me: "Exposure to red light seemed beneficial in one experiment but subsequent treatments cast doubt on those results."
Since about 1990 I have been germinating my rose seeds in a sun room that has windows on the north, west, and east side. I noticed that I had the earliest germination in containers that were placed on the north side near to the west side. In this position the seeds, which were sitting on a wet surface and enclosed in clear containers, received direct sunlight only in the evening (the red light of the setting sun).
In 1995 Y. Yambe, K. Takeno, and T. Saito published a paper titled: "Light and Phytochrome Involvement in Rosa multiflora Seed Germination": in J. Amer. Soc. Hort. Sci. 120,953-955(1995).
The abstract is: " Seed germination percentage of multiflora rose (Rosa multiflora Thunb.) was much higher under continuous white light than in complete darkness. Red light was the most effective in inducing germination, and far-red light was ineffective. Exposure to red light for 1 min increased germination; this effect was saturated at an exposure of 2 min. The red-light effect was reversed by subsequent exposure to far-red light. The results indicate that rose seeds are positively photoblastic, and that the photoreceptor involved is most likely phytochrome."
Their "Results and Discussion" section starts with the following: "Germination percentage was >60% under light, whereas germination in darkness was negligible".
Although the main study was on rosa multiflora seeds, the authors did make the following statement: "Preliminary experiments with seeds of R hybrida 'Inspiration' resulted in a similar conclusion (data not presented)".
An explanation for the red light enhancement of seed germination is: nature has provided the seeds with a mechanism by which they can detect whether they are close enough to the soil surface to survive if they would germinate (see for example, page 192, Plant Propagation, Sixth Edition, by H. T. Hartmann, D.E Kester, F.T. Davis, and R. L. Geneve, Prentice Hall publisher, 1997). Of the various components of sun light, it is the red part of the spectrum that is able to penetrate a short distance into the soil.
I now cover my seed trays with red transparent wrapping paper. Probably the easiest type to find and use is the red colored form of transparent cling food wrap such as the Handi-Wrap Brand Plastic Film or clear red wrapping paper found in party stores.