Abstract

Among the factors affecting seed germinability 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 seed quality in lettuce. Seeds of 'Tango' were produced in growth chambers under one of two treatments: i) short day (SD), consisting of 8h fluorescent light plus 16h of darkness, and ii) long day (LD), consisting of 8h fluorescent light plus 8h of incandescent light and 8h of darkness. The LD treatment produced significantly heavier seeds (?13% higher dry weight). When germinated in water at 20°C and in continuous light. There were no differences between SD and LD treatments in final germination percentage (GP), which was close to 100%. In treatments, GP and germination index (GI the sum of the ratio of germinated seeds to days after sowing at each count) were affected by increased exogenous ABA concentrations (from 0 to 100 ?M); however, seeds from LD were more sensitive to this compound. Reduced water potential (from 0 to -6 bars) also decreased GP and GI in both treatments, with a slight tendency of seeds from LD to be more affected. Seeds from SD presented average GP of 57, 62, 33, and 0% when evaluated in the dark at 14, 19, 24, and 29°C, respectively, whereas LD the GP was close to 0% at all these temperatures. Results therefore indicated that day-length during lettuce seed development not only affected seed weight but also seed germinability under sub-optimal conditions: seeds produced under shorter days were lighter, less sensitive to exogenous ABA and had greater dark germination percentage.