Longevidade in situ e defesa química em sementes de Syngonanthus (Eriocaulaceae) dos campos rupestres de Minas Gerais, Brasil

Abstract

(Ecophysiology of seed germination in Syngonanthus species (Eriocaulaceae) from the rupestrian fields of the Espinhaço Chain, Minas Gerais, Brazil).The aim of this study was to evaluate the biometry and the germinative characteristics of seeds of seven Syngonanthus species, distributed in four distinct sections within the genus, occurring in different habitats in the rupestrian fields of Minas Gerais intending to answer these questions: Is there similarity in seeds biometry between distinct Syngonanthus sections? Is there a pattern in the germinative answers between the different sections of the genus? Do Syngonanthus species germinative characteristics have an influence on their geographical distribution? Can species germinative answers be associated with the water saturation conditions that these species are naturally exposed in the soil? The experiments were made with recently harvested seeds under a 12 - hour photoperiod and continuous darkness in germination chambers, at constant temperatures of 10 to 40 ºC (intervals of 5 ºC). Although the variability existing in the seed size the results showed that, all seeds are very small and photodorments, indicating the existence of a pattern related to the small size and light requirements for germination. The temperature requirement does not explain the geographical distribution of the Syngonanthus species, but the temperature limits for germination showed a relation between habitat and germinative answers. These results indicate that the studied populations are adapted to climatic and edaphic conditions similar to those found in the rupestrian fields.