RESUMO -A alface (Lactuca sativa L.) é uma das folhosas de maior importância na cadeia produtiva de hortaliças. O estabelecimento da lavoura de alface pode ser feito por meio da semeadura direta ou transplantio de mudas. As sementes apresentam particular sensibilidade às variações de temperatura do meio onde germinam. Condições de alta temperatura, por exemplo, afetam negativamente a germinação e o estabelecimento de plântulas. O objetivo neste trabalho foi identificar as diferenças de germinação de sementes de vinte cultivares de alface em condições de temperatura ideal 20 ºC, temperatura intermediária 27,5 ºC e temperatura crítica 35 ºC. Utilizaram-se sementes comerciais adquiridas de empresas, bem como sementes das mesmas cultivares produzidas na Embrapa Hortaliças, em condições de casa de vegetação. Alguns genótipos termotolerantes Vitória de Verão e Camila foram identificados, obtendo germinação acima de 90% nas temperaturas: favorável e crítica máxima. Estes genótipos poderiam ser utilizados como fonte genética de tolerância à germinação a altas temperaturas. Para as sementes produzidas na casa de vegetação, a maioria não germinou satisfatoriamente em condições de altas temperaturas.Termos para indexação: Lactuca sativa, estabelecimento de plântulas, termo-inibição, termo-dormência.Seed production, physiological quality and identification of thermotolerant lettuce genotypes ABSTRACT -Lettuce (Lactuca sativa L.) is one of the most important foliar crops in vegetable crop production and may be established by direct seeding or by transplanting. Seed germination is particularly sensitive to environmental temperature changes and high temperatures adversely affect germination and seedling establishment. The aim of this study was to identify differences in the germination of twenty lettuce cultivars under conditions of optimum (20 °C), intermediate (27.5 °C) and critical (35 ºC) temperatures. Commercial seed from different companies was used, as well as seeds of the same cultivars grown at the Embrapa Horticulture Institute under greenhouse conditions. Some thermotolerant genotypes, 'Vitória de Verão' and 'Camila', were identified, with more than 90% germination for the critical and optimum temperature conditions. These genotypes could be used as a source of genetic tolerance to germination at high temperatures. Most of the seed produced in a greenhouse did not germinate satisfactorily under high temperatures.

During seed extraction in fleshy fruits, some procedures are necessary to ensure seed quality and minimize deterioration and microorganism activity; also seeds extracted under moist conditions need special care when drying. The objective of this study was to evaluate the physiological quality of eggplant seeds submitted to different extraction and drying methods. In the first study, whole eggplant fruits were mechanically crushed and then fermented for 0, 24 and 48 hours, with and without applying hydrochloric acid during seed extraction. In the second study, seeds were extracted in a pepper peeler and then immediately washed in water and submitted to the following drying methods: Sun/24 h; Sun/48 h; 32 °C/24 h; 32 °C/48 h; 38 °C/24 h; 38 °C/48 h; Sun/24 h + 32 °C/24 h; Sun/24 h + 38 °C/24 h e 32 °C/24 h + 38 °C/24 h. The treatment efficiency of both experiments was evaluated from the following tests: seed weight, germination, first count, accelerated aging and seedling emergence. The results suggest that fermentation and applying hydrochloric acid to pulp/seed reduce the physiological seed quality. All drying methods reduced the seed moisture content permitting adequate storage and maintenance of seed physiological quality.