Preventing thermoinhibition in a thermosensitive lettuce genotype by seed imbibition at low temperature

Abstract

Lettuce (Lactuca sativa L.) seed germination is strongly temperature dependent and under high temperatures, germination of most of genotypes can be erratic or completely inhibited. Lettuce seeds of 'Dark Green Boston' (DGB) were incubated at temperatures ranging from 15° to 35°C at light and dark conditions. Other seeds were imbibed in dark at 20°; 25°; 30°; and 35°C for 8 and 16 hours and then transferred to 20 or 35°C, in dark. Seeds were also incubated at constant temperature of 20° and 35 °C, in the dark, as control. In another treatment, seeds were primed for 3 days at 15°C with constant light. DGB lettuce seeds required light to germinate adequately at temperatures above 25°C. Seeds incubated at 20°C had 97% germination, whereas seeds incubated at 35°C did not germinate. Seeds imbibed at 20°C for 8 and 16 hours had germination. At 35°C, seeds imbibed initially at 20°C for 8 and 16 hours, had 89 and 97% germination, respectively. Seeds imbibed at 25°C for 16 hours, germinated satisfactory at 35°C. High temperatures of imbibition led to no germination. Primed and non-primed seeds had 100% germination at 20°C. Primed seeds had 100% germination at 35°C, whereas non-primed seeds germinate only 4%. The first hours of imbibition are very critical for lettuce seed germination at high temperatures.

Physiological and biochemical changes in lettuce seeds during storage at different temperatures

“…Everglades maintained high germination throughout storage in all environments (Table 1). The Everglades seed germination decreased from 74% to 68% germination over the whole storage period, indicating its superiority in tolerating adverse conditions, as was also observed in other studies (Nascimento, 2003;Kozarewa et al, 2006). These results indicate Everglades as a potential genotype for breeding programs.…”

Produção de sementes, qualidade fisiológica e identificação de genótipos de alface termotolerantes

“…Em estudos realizados por Nascimento e Pereira (2002), avaliando a germinação de sementes de alface sob altas temperaturas, foram observadas diferenças entre as cultivares. A germinação de sementes de alface é extremamente dependente da temperatura, e sob condições de altas temperaturas, a germinação da maioria dos genótipos pode ser errática ou completamente inibida (Nascimento, 2003). O mecanismo de ação da germinação de sementes de alface em altas temperaturas parece estar relacionado com o enfraquecimento do endosperma, o qual não permite o crescimento do embrião (Nascimento, 2003).…”

Germination temperatures affect the physiological quality of seeds of lettuce cultivars

“…Temperature ( Reduction rate in germination occurs after increases of 5°C from 20°C and 25°C, except for 'Everglades' and 'Grand Rapids'. According to Nascimento (2003), the optimum temperature to achieve normal lettuce seedlings is approximately 20°C.…”

“…The mechanism of action for lettuce seeds germination at high temperatures seems to be related to the weakening of the endosperm, which allows the embryo to grow at elevated temperatures. The first hours of imbibition are critical for germination under high temperature conditions, since the embryo is fully included in the endosperm, where the radicle must penetrate to grow and complete the germination process (NASCIMENTO, 2003;NASCIMENTO et al, 2004).…”