An Effective Post-sown Priming Method to Improve Emergence from Lettuce Seeds at High Temperature

ADDITIONAL INDEX WORDS. Lactuca sativa, plug seedling, seed treatment SUMMARY. A study was conducted to improve the seedling emergence rate of lettuce (Lactuca sativa) seeds at high temperatures using a convenient postsown priming method. Seeding mixtures adjusted to 35%, 45%, or 55% moisture content were sown with lettuce ‘Patriot’ in cell trays. Postsown priming was performed at 20 � C for 1 day and at 30 � C for 3 or 5 days. After the treatment, trays were moved to an emergence room kept at 32.5 � C, a temperature assumed to be typical of non-airconditioned rooms in nurseries. Emergence of nonprimed controls was 9% to 16% after 2 days in the emergence room and was 59% to 75% on day 6. In contrast, seedling emergences on day 2 were 95%, 76%, and 78% to 79% in 55% moisture at 20 � C for 1 day, 55% moisture at 30 � C for 3 days, and 45% to 55% moisture at 30 � C for 5 days, respectively. Therefore, the treatment with 55% moisture at 20 � C for 1 day appeared most effective; however, post-sown priming with 55% moisture at 30 � C for 3 days or 45% to 55% moisture at 30 � C for 5 days may be more practical due to lower temperature-control costs.