Temperature Requirements for the Storage and Germination of Delphinium × cultorum Seed

Abstract

Delphinium seed germination was about equal in light or darkness. Seed total germination percentages were highest and about equal at constant 15 or 20C and alternating (12 h) 10/20C, 15/25C, or 20/30C. The most rapid and uniform germination generally occurred at constant 20C. Storing seeds dry at 2C for 3 weeks before germination reduced the days to 50% of final germination (T 50 ) and between 10% and 90% germination (T 90 - T 10 ) but did not increase total germination. The seeds had only limited desiccation tolerance, with `Magic Fountains Lavender' having declining germination percentages at moisture contents below 7.0% and `Magic Fountains Lilac' below 6.7%. Seeds tolerated storage at low, nonfreezing or subzero temperatures, but cultivar responses differed. `Magic Fountains Lavendar' had progressively lower germination percentages as storage temperatures declined from 5 to –20C, while `Magic Fountains Lilac' germination increased. The relative humidity (RH) and temperature that delphinium seed received during long-term storage influenced germination. Germination after seed storage at 5C was higher, earlier, and more uniform than after 15 or 25C storage. The highest total germination percentages occurred following seed storage at 5C and 30% to 50% RH, the shortest T 50 from 35% to 55% RH, and shortest spans (T 90 - T 10 ) from 25% to 50% RH.