Profiles of hydration and nonstructural carbohydrates during seed germination in Cenostigma pyramidale
Seeds, imbibition, reserve mobilization
Considering the importance of seed germination to forest regeneration, this work aimed to determine the patterns of hydration and non-structural carbohydrates in the seeds of Cenostigma pyramidale during this process. The sowing was performed between Germitest® paper sheets humidified with distilled water and the seeds were incubated under controlled conditions up to 72 h. The water content was determined in the intact seeds, testa, embryo axis and cotyledons, the contents of starch, soluble proteins, total soluble sugars, non-reducing sugars, and total free amino acids were assessed in the embryo axis and cotyledons, and the content of neutral lipids was measured only in the cotyledons. The seeds presented a triphasic hydration curve during germination, but the phase I showed an atypical pattern as hydration was slow during its beginning and was intensified during its end. This hydration slow step could be attributed to the testa, since water uptake was faster in the embryo axis and cotyledons than in the testa during the beginning of the phase I. During germination, the mobilization of storage proteins was not detected in the embryo axis and cotyledons, but the storage lipids were partially mobilized at the beginning of phase I and during phase II. As the mobilization of these reserves coincided with the accumulation of starch and soluble sugars in the embryo axis and cotyledons, these non-structural carbohydrates may be derived from storage lipids. Variations in the content of free amino acids during the phases I and II could be related to protein turnover during metabolism reactivation.