Chemical scarification of seeds and substrates for the cultivation of seedlings of melocactus zehntneri

Resumo

The populations of Melocactus zehntneri have been presenting alarming decline due to the constant removal of individuals from their natural areas for commercial purposes, being popularly known and sold as chapéu-de-frade.  In view of this fact and the reduced percentage of germination of Melocactus seeds, added to the slowness of its post-germination development, this species needs alternatives for its commercial propagation and reduction of the removal of individuals from their natural areas for commercial purposes, aiming its use as an ornamental plant. Thus, this study aimed to test the influence of hydrochloric acid and acetic acid on the germination of seeds of M. zehntneri in Petri dishes, and the influence of different substrates on the initial development of individuals of the species. The seeds were immersed in deionized water, hydrochloric acid (5N) and glacial acetic acid (100%) for 10, 20, 30, 40 and 50 minutes and placed to germinate in Petri dishes containing filter paper moistened with 5 mL of deionized water solution containing 2 mL L^-1  of chlorine dioxide. The seedlings obtained from this germination (≡ 0.4 cm diameter) were individually arranged in the substrates Carolina Soil® and vermiculite (I) [2:1]; Carolina Soil® and vermiculite [2:1] + drainage (I.i); medium-grained sand (II); medium-grained sand + drainage (II.i); medium grained sand and organic compost (III) [1:1]; medium grained sand and organic compost [1:1] + drainage (III.i); and Carolina Soil® and medium grained sand (IV) [1:1]. The highest percentage of germination was obtained with pre-treatment by immersion in water at the times of 10 and 30 minutes, totaling 55% of germinated seeds. The treatments with hydrochloric acid didn’t increase the percentage of germinated seeds, which were also close to 50%. In the test with substrates, the treatments containing the substrate Carolina Soil® showed the best survival rates of seedlings after transplanting (87.5%) and performance of seedling development. The treatments containing organic compost showed inferior results of survival (69%) and development of the seedlings. From the results, its concluded that artificial propagation, by germination of seeds in Petri dishes, followed by transplanting and development of seedlings in commercial substrates under greenhouse conditions is an excellent alternative for production of seedlings of M. zehntneri on a commercial scale.