Temperature during seed development affects weight, germinability and storability of lettuce seeds.

Seed germinability and storability are important aspects of lettuce seed quality determined by the genotype and environment of seed development. The objective of this study was to determine how temperature of the mother plant environment affects lettuce seed quality. Seeds of cv. Tango were produced in growth chambers under one of two treatments: i) high temperature (HT), with day/night temperatures of 30/20°C, respectively, and ii) low temperature (LT), with temperatures of 20/10°C. Seeds produced at LT were 37% heavier than seed from HT, however germination at optimal conditions (20°C-light) was similar for both treatments. Seeds from HT presented higher dark germination at 18, 24 and 29°C. Germinability (% and rates) under light at temperatures between 20 and 30°C was similar for seeds from both treatments, however at temperatures between 30 and 40°C seeds from HT performed better than those from LT. When germinated at exogenous abscisic acid concentrations or negative osmotic potentials, germinability of seed from HT was less affected than LT. After accelerated aging (41°C, ~100%RH, 72 h), germination of normal seedlings was higher for seeds from HT. Germination after 1 and 2 months of storage at 30°C and 74% RH was better for seeds from HT. The critical moment for temperature effects was also studied. Seed weight, dark germination at 30°C and germination at low osmotic potential were shown to be determined earlier during seed development (before 5 and 4 d after flowering for seeds from LT and HT, respectively). On the other hand, seed storability was determined at the end of seed development, after physiological maturity (≈ 16 and 11 d after flowering for LT and HT seeds, respectively). In conclusion, higher ‘Tango’ lettuce seed germinability and storability results were attained when seeds were produced at higher temperatures.