Psysiological maturing and dormancy in seeds of Parkia platycephala Benth. (Fabaceae)

Abstract

The germination capacity of freshly harvested legume seeds is controlled by two antagonistic processes, the maturation process and the establishment of tegument dormancy. Current analysis, foregrounded on the change of color of the fruits, determines, throughout the maturation process of Parkia platycephala seeds, when: i) the seeds reach the germination capacity and ii) the dormancy of the integument is imposed. It also evaluates the efficacy of methods to overcome the dormancy of the species. Two experiments were carried out: (I) assay with a completely randomized design, 2 x 6 (with and without breaking dormancy x six maturation stages); (II) completely randomized design, with 23 treatments to overcome dormancy. Both assays comprised four replications of 25 seeds each. In experiments I and II, the following variables were evaluated: moisture content, germination percentage, germination speed index, shoot length and primary root, shoot dry mass and seedling root system. Results showed a gradual increase in germination capacity, vigor and establishment of the dormancy mechanism with the reduction of water content and occurrence of physiological maturation. Seed germination capacity occurred prior to dormancy; however, seeds have low physiological quality and high wa-ter-contents. Mechanical scarification with sandpaper and immersion in sulfuric acid for 20 minutes are the most efficient methods for breaking dormancy.