Seed longevity, defined as the ability to remain alive during storage, is an important agronomic factor. Poor longevity negatively impacts seedling establishment and consequently crop yield. This is particularly problematic for soybean as seeds have a short lifespan. While the economic importance of soybean has fueled a large number of transcriptome studies during embryogenesis and seed filling, the mechanisms regulating seed longevity during late maturation remain poorly understood. Here, a detailed physiological and molecular characterization of late seed maturation was performed in soybean to obtain a comprehensive overview of the regulatory genes that are potentially involved in longevity. Longevity appeared at physiological maturity at the end of seed filling before maturation drying and progressively doubled until the seeds reached the dry state. The increase in longevity was associated with the expression of genes encoding protective chaperones such as heat shock proteins and the repression of nuclear and chloroplast genes involved in a range of chloroplast activities, including photosynthesis. An increase in the raffinose family oligosaccharides (RFO)/sucrose ratio together with changes in RFO metabolism genes was also associated with longevity. A gene co-expression network analysis revealed 27 transcription factors whose expression profiles were highly correlated with longevity. Eight of them were previously identified in the longevity network of Medicago truncatula, including homologues of ERF110, HSF6AB, NFXL1 and members of the DREB2 family. The network also contained several transcription factors associated with auxin and developmental cell fate during flowering, organ growth and differentiation. A transcriptional transition occurred concomitant with seed chlorophyll loss and detachment from the mother plant, suggesting the activation of a post-abscission program. This transition was enriched with AP2/EREBP and WRKY transcription factors and genes associated with growth, germination and post-transcriptional processes, suggesting that this program prepares the seed for the dry quiescent state and germination.

The aim of this study was to adapt the methodology of the accelerated aging and electrical conductivity tests for determination of physiological potential in crambe seeds. Six seed lots of crambe (cv. FMS Brilhante) were subjected to determination of moisture content, germination test, first count germination, emergence, and emergence speed index. For the accelerated aging test, the traditional methodology was used with water, and with a saturated potassium chloride and sodium chloride solution in three periods of exposure (24, 48, and 72 hours) at 41°C; the electrical conductivity test was performed with four pre-soaking treatments (0, 2, 4, and 8 hours) and four soaking periods (4, 8, 16, and 24 hours) at 25°C. The accelerated aging test with water for 72 hours and the electrical conductivity test with 2 hours of pre-soaking and assessment after 16 hours were effective for classification of the crambe seed lots in regard to physiological quality. Index terms:Crambe abyssinica, vigor, physiological quality. RESUMOConduziu-se esta pesquisa, com o objetivo de adequar a metodologia dos testes de envelhecimento acelerado e condutividade elétrica para determinação do potencial fisiológico em sementes de crambe. Seis lotes de sementes de crambe cultivar FMS Brilhante foram submetidos à determinação do teor de água, teste de germinação, primeira contagem de germinação, emergência, índice de velocidade de emergência. Para o teste de envelhecimento acelerado, foi utilizada a metodologia tradicional com o uso de água e com solução saturada de cloreto de potássio e cloreto de sódio em 3 períodos de exposição (24, 48 e 72 horas) a 41°C; o teste de condutividade elétrica foi realizado com quatro tratamentos de pré-embebição (0, 2, 4 e 8 horas) e quatro períodos de embebição (4, 8, 16 e 24 horas) a 25°C. O teste de envelhecimento acelerado com água por 72 horas e o teste de condutividade elétrica com 2 horas de pré-embebição e avaliação, após 16 horas, foram eficientes para a classificação dos lotes de sementes de crambe quanto à qualidade fisiológica. Termos para indexação:Crambe abyssinica, vigor, qualidade fisiológica.

-The objective of this research was to evaluate the effects of different drying methods on physiological quality of crambe seeds. Crambe seeds of FMS Brilhante cultivar were produced in the Lageado experimental farm (UNESP, Botucatu, Brazil) in 2012. The drying methods were: artificial drying with hot air, artificial drying with fresh air, natural yard drying, natural shade drying and natural field drying. The water content of seeds was monitored before, during and after drying. Germination, first germination count, abnormal seedlings, GSI, germination synchronization, frequency and germination mean time, electrical conductivity, fatty acid index and oil content were evaluated in order to know the physiological quality. The experimental design was randomized and the averages compared by the t-test at 5% significance. Results showed that artificial hot air drying favored with higher germination and vigor of crambe seeds when compared to other drying methods and demanded shorter time to reduce the water content. The natural shade drying method is feasible for crambe seeds despite taking longer.Key words: Natural drying. Artificial drying. Crambe seeds vigor. Seeds damage.RESUMO -Objetivou-se nesta pesquisa avaliar o efeito de diferentes métodos de secagem na qualidade fisiológica de sementes de crambe. As sementes de crambe da cultivar FMS Brilhante foram produzidas na Fazenda Experimental Lageado (UNESP -Botucatu) no ano de 2012. As condições de secagem foram: secagem artificial com ar aquecido, secagem artificial com ar natural, secagem natural em terreiro, secagem natural à sombra e secagem na planta. O teor de água foi monitorado antes, durante e após a secagem. Para avaliação da qualidade fisiológica foi realizado o teste de germinação, primeira contagem de germinação, plântulas anormais, IVG, sincronização da germinação, frequência e tempo médio de germinação, teste de condutividade elétrica, índice de acidez graxa e teor de óleo. O delineamento experimental foi inteiramente casualizado e as médias comparadas pelo teste de Tukey a 5% de significância. Pelos resultados obtidos a secagem artificial com alta temperatura favoreceu obtenção de sementes de crambe com alta germinação e vigor em relação aos demais tipos de secagem com um tempo menor para redução do teor de água. A secagem natural na sombra é viável para sementes de crambe apesar de ser longa.Palavras-chave: Secagem natural. Secagem artificial. Vigor de sementes de crambe. Danos em sementes.