Seed germination performances of Styrax species help understand their distribution in Cerrado areas in Brazil

Abstract

In this descriptive paper, we described germination responses of Styrax pohlii, S. camporum and S. ferrugineus seeds at 5, 10, 15, 20, 25, 30, 35, 40 and 45 °C. We also assessed the percentage germination (%G) of S. pohlii seeds with different seed water contents because, as a forest species, it seems to have recalcitrant seed behavior. Intrigued by the capacity of seeds of this species to germinate directly from puddles formed on poorly drained soils of riparian forests, where it typically occurs, we also tested the effect of de-pulping fruits on germination of S. pohlii seeds under hypoxia and normoxia conditions. In addition, we checked whether distinct concentrations of gibberellic acid (GA 3 ) could break S. ferrugineus seed dormancy, a typical seed behavior of Cerrado species. No germination occurred at 5, 40 and 45 °C, regardless of the species. The optimal temperature for germination was 20 °C for S. pohlii and 25 °C for S. camporum. However, S. ferrugineus seeds showed a very low %G, regardless of the temperature, and GA 3 could not consistently break possible physiological seed dormancy. For S. pohlii seeds, the higher the seed desiccation the lower the %G, and fruit pulp removal showed to be essential for seed germination. S. pohlii seeds germinated independently of oxygenation conditions. Key words: hypoxia, Styrax pohlii, S. camporum, S. ferrugineus, temperature, desiccation seed tolerance.Desempenho germinativo de sementes de espécies de Styrax ajuda a entender sua distribuição em áreas de Cerrado no Brasil ResumoNeste trabalho descritivo foi mostrada a resposta germinativa das sementes de Styrax pohlii, S. camporum e S. ferrugineus a 5, 10, 15, 20, 25, 30, 35, 40 e 45 °C. Avaliou-se também a porcentagem de germinação (%G) de sementes de S. pohlii com diferentes conteúdos de água, pois, por ser uma espécie florestal, suas sementes parecem ser recalcitrantes. Dada a capacidade de as sementes dessa espécie germinarem diretamente em poças d'água formadas em solos mal drenados nas florestas ripárias, onde a espécie tipicamente ocorre, também testou-se o efeito do despolpamento dos frutos para a germinação de sementes de S. pohlii em condições de hipóxia e normóxia. Além disso, verificou-se se diferentes concentrações de ácido giberélico (GA 3 ) poderiam quebrar a dormência das sementes de S. ferrugineus, que é característica de sementes de espécies do Cerrado. Não houve germinação a 5, 40 e 45 °C, independente da espécie. A temperatura ótima para a germinação foi 20 °C para S. pohlii e 25 °C para S. camporum. Porém, as sementes de S. ferrugineus mostraram %G muito baixa, independente da temperatura, e o GA 3 não quebrou consistentemente a possível dormência fisiológica dessas sementes. Para as sementes de S. pohlii, quanto maior a dessecação, menor %G, e a remoção da polpa dos frutos mostrou ser essencial para a germinação das sementes. As sementes de S. pohlii germinaram independentemente das condições de oxigenação.Palavras-chave: hipóxia, Styrax pohlii, S. camporum, S. ferrugineus, temperat...

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