Effects of scarification methods on dormancy break of seeds and of substrates on germination and on development of grápia (Apuleia leiocarpa)

Grápia (Apuleia leiocarpa) has dificulties to be propagated via seeds, due to the long germination period and its irregularity, caused by the tegument impermeability. The aim of this study was to develop a reliable method to facilitate the seedling production of this species, an endangered Brazilian forest tree. Thus, several experiments were carried out to test the effect of boiling water and concentrated sulfuric acid (H2SO4) with different imersion periods (15s, 30s, 1min, 2min; and 30s, 2min, 5min, 10min, 20min, respectively) on seed, collected on two regions of Brazil. Concerning the substrate effects on germination and development of seedlings, the treatments consisted of a mixture (1:1v/v) of the following substrates: sand + carbonized rice husk, sand + soil, soil + carbonized rice husk, and soil alone. The results allowed to conclude that: (i) the H2SO4 is efficient to overcome impermeability of seed coat, and the best results are gotten when the imersion period is higher than 2 min (90% of germination after 5 days of H2SO4 application); (ii) seed imersion in boiling water is not recommended (100% of death); (iii) the tradicional method, without scarification of the seed tegument, for germination induction is impracticable due to the long waiting time and by the large desuniformity; and (iv) there is no effect of the types of substrates on seed germination but, on the other hand, the combination of sand + carbonized rice husk is one of the best substrate on the seedling growth.

Apuleia leiocarpa; seeds; dormancy; germination; substrates; seedling