Metabolismo de sementes de Annona emarginata (Schltdl.) H. Rainer durante tratamentos de imersão em soluções aquosas
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Data
2016-02-26
Autores
Gimenez, Juliana Iassia [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O presente estudo objetivou avaliar como a imersão de sementes até atingirem determinados teores de água durante a embebição altera o metabolismo e a germinabilidade. Sementes de Annona emarginata (Schltdl.) H. Rainer inicialmente com 10% de água foram submetidas à embebição entre papel umedecido com água ou sob imersão em Ψw 0 MPa ou em Ψw -1,2 MPa até atingirem os teores de 15%, 20% e 35% de água. Durante os tratamentos foram monitorados o teor de água, produção de etanol e a atividade respiratória das sementes. À medida que as sementes atingiram os teores de água foram retiradas dos tratamentos para as análises: teste de germinação, análise anatômica e ultraestrutural do embrião, quantificação de açúcares solúveis totais e perfil (glicose, frutose e sacarose), amido, proteínas solúveis totais e perfil (albuminas, globulinas, glutelinas e prolaminas), lipídeos totais e hormônios vegetais (ABA e IAA), atividade de enzimas antioxidantes (Superóxido Dismutase, Catalase e Peroxidase) e peroxidação de lipídeos. À medida que os teores de água foram alcançados ao longo do tempo de imersão até completar a embebição (final da fase I) ocorreu a redução na disponibilidade de oxigênio (hipoxia) cujos níveis críticos provocaram danos metabólicos (alterações na atividade respiratória, no perfil hormonal (ABA/IAA), na degradação de reservas e no sistema antioxidante) e ultraestruturais, que resultaram em decréscimo da germinabilidade demonstrando intolerância à hipoxia pelas sementes de A. emarginata. Conclui-se que o fator limitante durante a embebição de sementes em soluções aquosas e que pode auxiliar a definir o tempo de imersão é a determinação do nível crítico de disponibilidade de oxigênio, a fim de evitar danos irreversíveis que resultem em redução da germinabilidade.
The present study aimed to assess how seed immersion until they reach different water contents during the imbibition phase changes its metabolism and germination. Seeds of Annona emarginata (Schltdl.) H. Rainer initially with 10% of water content were imbibed on moistened paper or immersed in Ψw 0 MPa or in Ψw -1.2 MPa until they reach 15%, 20% and 35% threshold of water content. Seed water content, ethanol production and respiration were monitored during treatments. When achieved each water content threshold, seeds were removed and the following analysis carried on: germination test, embryo anatomy and ultrastructure, quantification of total soluble sugars and profile (albumin, globulin, glutelin and prolamin), total lipids and plant hormones (ABA and IAA), antioxidant enzymes activity (Superoxide dismutase, Catalase and Peroxidase) and lipid peroxidation. Oxygen availability was reduced (hypoxia) as water content thresholds were achieved throughout immersion time until complete imbibition (end of phase I), these critical levels caused metabolic (changes in respiratory activity, hormone profile (ABA/IAA), reserve degradation and antioxidant system) and ultrastructural damages, which resulted in germination decrease demonstrating that A. emarginata seeds are hypoxia intolerant. It can be concluded that the limiting factor during imbibition in aqueous solutions is the assessment of critical level of oxygen availability, which might help to define the limit for immersion time in order to avoid irreversible damage that results in decreased germinability.
The present study aimed to assess how seed immersion until they reach different water contents during the imbibition phase changes its metabolism and germination. Seeds of Annona emarginata (Schltdl.) H. Rainer initially with 10% of water content were imbibed on moistened paper or immersed in Ψw 0 MPa or in Ψw -1.2 MPa until they reach 15%, 20% and 35% threshold of water content. Seed water content, ethanol production and respiration were monitored during treatments. When achieved each water content threshold, seeds were removed and the following analysis carried on: germination test, embryo anatomy and ultrastructure, quantification of total soluble sugars and profile (albumin, globulin, glutelin and prolamin), total lipids and plant hormones (ABA and IAA), antioxidant enzymes activity (Superoxide dismutase, Catalase and Peroxidase) and lipid peroxidation. Oxygen availability was reduced (hypoxia) as water content thresholds were achieved throughout immersion time until complete imbibition (end of phase I), these critical levels caused metabolic (changes in respiratory activity, hormone profile (ABA/IAA), reserve degradation and antioxidant system) and ultrastructural damages, which resulted in germination decrease demonstrating that A. emarginata seeds are hypoxia intolerant. It can be concluded that the limiting factor during imbibition in aqueous solutions is the assessment of critical level of oxygen availability, which might help to define the limit for immersion time in order to avoid irreversible damage that results in decreased germinability.
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Palavras-chave
Ácido abscísico, Annonaceae, Degradação de reservas, Embebição, Respiração, Sistema antioxidante, Abscisic acid, Annonaceae, Antioxidant system, Degradation of reserves, Imbibition, Respiration