Imbibition curve in forest tree seeds and the triphasic pattern: theory versus practice

Abstract

Although providing the basis for seed germination studies, there is little information available on seed imbibition curves for Brazilian forest species. Among the few studied species, the theoretical triphasic pattern may not apply, hampering the conduction of subsequent studies that require a clear definition of imbibition phases. In this paper, we characterize the seed imbibition curves of 25 Brazilian forest species and compare them with those from other studies and with the classic triphasic pattern. We collected seeds of the chosen species in the region of Lavras, MG, Brazil, and measured their fresh weight before and during the entire germination process. Seed weight data were used to calculate the weight gain percentage of each species. We defined the imbibition curves of Peltophorum dubium seeds using seed fresh weight and seed weight gain percentage of both single and multiple samples, as well as using water content (on fresh and dry bases) to compare potential changes in imbibition patterns caused by differences in data. When only weight gain was considered, we observed the triphasic pattern in 11 species; however, only in four of them, the germination coincided with the third phase of imbibition. The triphasic pattern did not emerge for the remaining 14 species. Considering seed water content instead of weight resulted in some changes in the pattern of the imbibition curve, influencing the accuracy of the results.