Mecanismo de dormência em sementes de Annona cacans Warm. (Annonaceae)
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Data
2017-02-22
Autores
Dalanhol, Samanta Jaqueline [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Sementes dormentes de Annona cacans Warm. não respondem ao tratamento com giberelina como observado em outras espécies da família Annonaceae. Mesmo sendo permeáveis à água, é sugerida a escarificação do tegumento das sementes para melhorar sua germinação, fato que se deve possivelmente aos compostos fenólicos presentes na sua composição. Além disso, é recomendado o repouso dos frutos após a coleta, sem o conhecimento do que isto poderia acarretar à germinação e dormência das sementes. O objetivo deste estudo foi avaliar se o repouso após a coleta dos frutos e o tegumento estão envolvidos na dormência de sementes de Annona cacans. Para avaliar o efeito do repouso dos frutos sobre a germinação, as sementes foram beneficiadas logo após a coleta e a cada dois dias até completar o período de dez dias, sendo avaliadas as características físico-químicas dos frutos e a germinabilidade das sementes a cada época. Para investigar como os compostos fenólicos estão envolvidos com a dormência das sementes, estudou-se o efeito da escarificação e da embebição em regulador nas sementes ao longo do tempo e, para tanto, foram avaliados a germinabilidade, a anatomia das sementes, o teor de fenóis totais, a atividade da enzima polifenoloxidase (PPO), a atividade respiratória das sementes, o hormônio GA4 e a atividade de enzimas hidrolíticas. O repouso após a coleta dos frutos por até os quatro dias causa aumento na dormência das sementes, e a partir deste momento, observa-se perda gradativa da viabilidade das sementes conforme o tempo que estas permanecem nos frutos. Observou-se efeito sinérgico da escarificação das sementes e a embebição em regulador, pois estes tratamentos em conjunto aumentam a velocidade e a sincronização da germinação, além de apresentarem maior atividade respiratória e elevado teor de GA4 após a embebição, o que aumentou a atividade de enzimas amilolíticas e proteolíticas neste mesmo período, contribuindo para a superação da dormência dessas sementes. Conclui-se que o repouso após a coleta dos frutos é prejudicial à germinação de sementes de Annona cacans e que o tegumento intacto destas sementes promove condição natural de hipóxia ao embrião, o que contribui para a manutenção de sua dormência.
Dormant seeds of Annona cacans Warm. do not respond to treatment with gibberellin as observed in other species of the Annonaceae family. Although permeable to water, it is suggested seed coat scarification to improve its germination, a fact possibly due to the phenolic compounds present in its composition. In addition, it is recommended storage after fruit collection, without the knowledge of what this could induce to the germination and dormancy of the seeds. The aim of this study was to evaluate if the storage after fruit collection and the seed coat are involved in seed dormancy of Annona cacans. In order to evaluate the effect of the storage of the fruits on the germination, the seeds were benefited soon after the collection and every two days until completing the period of ten days, being evaluated the physical-chemical characteristics of the fruits and the germinability of the seeds at each time. To investigate how phenolic compounds are involved in seed dormancy, we studied the effect of seed scarification and seed imbibition in plant growth regulator over time, and, for this purpose, it were evaluated the germinability, seed anatomy, seed total phenols, polyphenoloxidase (PPO) activity, seed respiration, GA4 and activity of hydrolytic enzymes. Storage after fruit collection for up to four days causes an increase in the seed dormancy, but from this moment on, a gradual loss of the seed viability was observed according to the time they remain in the fruits. A synergistic effect of seed scarification and imbibition in regulator was observed, because these treatments together increase germination speed and synchronization, in addition it had higher respiratory activity and a high GA4 content after imbibition, which increased the activity of amylolytic and proteolytic enzymes in the same period, contributing to overcome seed dormancy. It is concluded that the storage after fruit collection is harmful to Annona cacans seed germination and that the seed coat promotes a natural condition of hypoxia to the embryo, which contributes to the maintenance of seed dormancy.
Dormant seeds of Annona cacans Warm. do not respond to treatment with gibberellin as observed in other species of the Annonaceae family. Although permeable to water, it is suggested seed coat scarification to improve its germination, a fact possibly due to the phenolic compounds present in its composition. In addition, it is recommended storage after fruit collection, without the knowledge of what this could induce to the germination and dormancy of the seeds. The aim of this study was to evaluate if the storage after fruit collection and the seed coat are involved in seed dormancy of Annona cacans. In order to evaluate the effect of the storage of the fruits on the germination, the seeds were benefited soon after the collection and every two days until completing the period of ten days, being evaluated the physical-chemical characteristics of the fruits and the germinability of the seeds at each time. To investigate how phenolic compounds are involved in seed dormancy, we studied the effect of seed scarification and seed imbibition in plant growth regulator over time, and, for this purpose, it were evaluated the germinability, seed anatomy, seed total phenols, polyphenoloxidase (PPO) activity, seed respiration, GA4 and activity of hydrolytic enzymes. Storage after fruit collection for up to four days causes an increase in the seed dormancy, but from this moment on, a gradual loss of the seed viability was observed according to the time they remain in the fruits. A synergistic effect of seed scarification and imbibition in regulator was observed, because these treatments together increase germination speed and synchronization, in addition it had higher respiratory activity and a high GA4 content after imbibition, which increased the activity of amylolytic and proteolytic enzymes in the same period, contributing to overcome seed dormancy. It is concluded that the storage after fruit collection is harmful to Annona cacans seed germination and that the seed coat promotes a natural condition of hypoxia to the embryo, which contributes to the maintenance of seed dormancy.
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Palavras-chave
Ácido abscísico, Compostos fenólicos, Giberelina, Hipóxia, Tegumento