Willian Naves Duarte

The seeds are used for conservation, genetic improvement and production of seedlings of native and cultivated species. However, seed dormancy has been a challenge, a process that prevents or delays germination, delaying or hindering their use in these applications. Thus, this study aimed to evaluate, understand and overcome, the seed dormancy in Rubus sellowii, a raspberry species native to Brazil. In our observations it was confirmed the existence of a rigid layer in seeds of R. sellowii that impedes water absorption. Seed scarification using sulfuric acid for 10 to 20 minutes increased the germination (up to 42.5% and 51.3%, respectively), and germination speed index (1.01 and 1.58), compared to no seed germination without scarification. Therefore, scarification was necessary and sufficient to overcome dormancy and allow the germination of R. selowii seeds. As well as in vitro experiments, the germination in substrate was favored by incubation under germination chamber conditions with day/night temperature alternation, improving R. sellowii seed germination. The alternation of temperature proved to be an important factor in controlling the germination of R. sellowii seeds.

Phalaenopsis is an orchid genus of great economic value in world floriculture. In vitro clonal propagation is the only large-scale feasible method for Phalaenopsis propagation, but it is difficult because of the low multiplication rate. The aim of this study was to evaluate the effect of types and concentrations of N⁶-benzyladenine (6-BA) and gibberellic acid (GA₃) on the in vitro multiplication of shoots from inflorescence nodal segments (INS) of Phalaenopsis hybrids. INS with one axillary bud were inoculated in New Dogashima Medium with different combinations of BA and GA₃. The results show that the treatment containing 1.0 mg L⁻¹ BA and 1.5 mg L⁻¹ GA₃ showed the higher percentage of live inflorescence segments (71.48%) and a number of shoots (1.68 shoots/INS). The highest 6-BA concentration (4 mg L⁻¹) tested in this study resulted in the best shoot multiplication rate (4.3). Contamination and browning of the INS tissues were the main difficulties identified for clonal propagation of Phalaenopsis. Successful in vitro rooting occurred on half-strength Murashige and Skoog medium (100%), and acclimatization (100%) was obtained independent of the substrates. However, the best gains in number of roots, leaves, chlorophyll content, and fresh weight of plantlets were achieved using vermiculite.