Day-Length During Seed Development Affects Germinability and Storability of Lettuce Seeds.
Samuel Contreras1, Mark Bennett1, and David Tay2. (1) Dept. of Horticulture and Crop Science, Ohio State Univ., 2021 Coffey Rd, Columbus, OH 43210, (2) Ornamental Plant Germplasm Center, Ohio State Univ., 670 Vernon Tharp St., Columbus, OH 43210
Among the factors affecting seed quality are the environmental conditions under which the seeds are produced. The objective of this study was to determine how day-length of the mother plant affects lettuce seed quality. Seeds of cv. Tango were produced in growth chambers under one of two treatments: i) short day (SD), consisting of 8 h of fluorescent light (~310 mmol·m-2·s-1) plus 16 h of darkness daily, and ii) long day (LD), consisting of 8 h of fluorescent light plus 8 h of incandescent light (~21 mmol·m-2·s-1) and 8 h of darkness daily. In both treatments the temperature was 23°C, constant. The LD treatment produced significantly heavier seeds, however germination at standard conditions (20°C-light) was similar for both treatments. At suboptimal conditions (30°C or 20°C with different external ABA concentrations), seeds from SD treatment exceeded seeds from LD in both germination percentage (GP) and germination index (GI, sum of the ratios of germinated seeds and days after sowing at the count moment). When germinated in dark at 13, 18, and 24°C, GP was significantly higher for seeds from SD; seeds from both treatments presented no germination at 29°C in dark. After accelerated aging (41°C, ~100%RH, 72 h) GP of normal seedlings was higher for seeds from LD. Seed germination was also evaluated after 2, 4, and 6 months of storage at two conditions: i) 30°C, 55% RH, and ii) 30°C, 74% RH. After the storage at the lower relative humidity, GP and GI at standard conditions remained similar for both treatments. Seeds stored at 74% RH presented a progressive and significant reduction of GP and GI for both treatments, however seeds from SD were more affected. The results indicated that dayl-ength during seed development affected lettuce seed weight, germinability, and storability. In this case, germinability and storability were inversely related.