Germinação de sementes de pau-ferro submetidas a diferentes condições de armazenamento, escarificação química, temperatura e luz
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Data
2007-01-01
Autores
Biruel, Rosangela Peres
Aguiar, Ivor Bergemann de [UNESP]
Paula, Rinaldo Cesar de [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Associação Brasileira de Tecnologia de Sementes (ABRATES)
Resumo
Caesalpinia leiostachya (Benth.) Ducke (pau-ferro) é uma planta arbórea nativa do Brasil, cujas sementes possuem dormência causada pela impermeabilidade do tegumento à água. Neste trabalho foram conduzidos dois experimentos, nos quais foram utilizados diferentes períodos de escarificação em ácido sulfúrico concentrado para superar a dormência das sementes. No primeiro experimento, sementes coletadas em agosto de 1997 foram armazenadas por oito meses em ambiente não controlado no interior do próprio fruto, e em câmara seca após serem extraídas dos frutos; a seguir, elas foram imersas em ácido sulfúrico por 0, 10, 20, 40, 60 e 80min e colocadas para germinar nas temperaturas constante de 25ºC e alternada de 20-30°C, sob fotoperíodo de 8h. No segundo experimento, sementes extraídas de frutos recém-coletados em agosto de 1998 foram imersas em ácido sulfúrico por 0, 10, 20, 30, 40 e 60min, seguido do teste de germinação conduzido nas mesmas temperaturas do experimento anterior, na ausência e presença de luz. Foram avaliados a porcentagem final e o índice de velocidade de germinação das sementes. Os resultados mostraram que (a) a manutenção das sementes no interior dos frutos é uma alternativa viável para o armazenamento durante o período adotado; (b) as sementes recém-coletadas são indiferentes à luz, nas duas temperaturas testadas; (c) as sementes recém-coletadas e as armazenadas germinam em maior velocidade a 25ºC; (d) em sementes armazenadas, a imersão em ácido sulfúrico por 10min é suficiente para superar a dormência; (e) em sementes recém-coletadas, a imersão em ácido sulfúrico por 20 a 30min favorece a porcentagem e a velocidade de germinação.
Caesalpinia leiostachya (Benth.) Ducke (Caesalpinaceae) is a tree species native to Brazil, whose seed dormancy is imposed by a waterproof coat. In this study two experiments using different periods of seed immersion in concentrated sulphuric acid in order to break dormancy were carried out. In the first experiment, seeds collected in August 1997 were stored for eight months either at room temperature inside the fruits or under dry chamber conditions after their extraction from the fruits. After storage, the seeds were immersed in sulphuric acid for 0, 10, 20, 40, 60, and 80 min and germination tests were conducted at constant (25ºC) and alternating (20-30ºC) temperatures, under an eight hour photoperiod. The second experiment was carried out with seeds extracted from fruits collected in August 1998 and immediately immersed in sulphuric acid for 0, 10, 20, 30, 40, 50, and 60min. Germination tests were conducted at 25ºC and 20-30ºC, in darkness and under white light. Both germination total percentage and speed of germination index were evaluated. The results showed that (a) the storage of seeds inside of fruits during the considered period is a viable alternative; (b) fresh seeds are indifferent to light at the two tested temperatures; (c) germination speed index either of fresh or of stored seeds is higher at 25ºC; (d) seed storage brought about a reduction in dormancy level so that exposing them to sulphuric acid for 10 minutes was enough to overcome seed dormancy; (e) in recently harvested seeds, the period of time of exposition to sulphuric acid needed to break dormancy was found to be between 20 and 30 minutes.
Caesalpinia leiostachya (Benth.) Ducke (Caesalpinaceae) is a tree species native to Brazil, whose seed dormancy is imposed by a waterproof coat. In this study two experiments using different periods of seed immersion in concentrated sulphuric acid in order to break dormancy were carried out. In the first experiment, seeds collected in August 1997 were stored for eight months either at room temperature inside the fruits or under dry chamber conditions after their extraction from the fruits. After storage, the seeds were immersed in sulphuric acid for 0, 10, 20, 40, 60, and 80 min and germination tests were conducted at constant (25ºC) and alternating (20-30ºC) temperatures, under an eight hour photoperiod. The second experiment was carried out with seeds extracted from fruits collected in August 1998 and immediately immersed in sulphuric acid for 0, 10, 20, 30, 40, 50, and 60min. Germination tests were conducted at 25ºC and 20-30ºC, in darkness and under white light. Both germination total percentage and speed of germination index were evaluated. The results showed that (a) the storage of seeds inside of fruits during the considered period is a viable alternative; (b) fresh seeds are indifferent to light at the two tested temperatures; (c) germination speed index either of fresh or of stored seeds is higher at 25ºC; (d) seed storage brought about a reduction in dormancy level so that exposing them to sulphuric acid for 10 minutes was enough to overcome seed dormancy; (e) in recently harvested seeds, the period of time of exposition to sulphuric acid needed to break dormancy was found to be between 20 and 30 minutes.
Descrição
Palavras-chave
Tree seed, dormancy, Physiological quality, Semente florestal, dormência, Qualidade fisiológica
Como citar
Revista Brasileira de Sementes. Associação Brasileira de Tecnologia de Sementes, v. 29, n. 3, p. 151-159, 2007.