Pre-sowing seed treatment with a temperature-drop influences plant growth and flowering in marigold and pansy.

The effects of a pre-sowing seed treatment with a temperature drop (i.e., seed thermo-priming) on the growth and development of two popular bedding plant species, Tagetes patula nana L. (marigold) and Viola X wittrockiana Gams. (pansy), were studied. A temperature drop from 22°C to 10°C was applied for 2 h each day during seed germination, over the 6 d before sowing. This seed priming increased plant dry mass, hastened flowering in both species, and increased flower numbers in marigold, but not in pansy. An involvement of certain phytochromes in these temperature-dependent effects on time-to-flowering is suggested. [ABSTRACT FROM AUTHOR]