Germinação de sementes e substratos para mudas de Melocactus zehntneri

Abstract

ABSTRACT The populations of Melocactus zehntneri 'chapéu-de-frade' have shown an alarming decline due to the constant withdrawal of individuals from their natural areas. The low percentage of germination of M. zehntneri seeds, added to the slow growth, requires a system for commercial propagation of this species. This study aimed to test the influence of water, hydrochloric acid or acetic acid pre-treatments on seed germination and the influence of different substrates on the initial development of M. zehntneri seedlings. The seeds were immersed in deionized water, hydrochloric acid (5N) or glacial acetic acid (100%) for 10, 20, 30, 40 and 50 minutes and placed to germinate in a Petri dish containing filter paper moistened with 5 mL deionized water. The seedlings obtained from this germination (≡ 0.4 cm diameter) were cultivated on Carolina Soil® and vermiculite [2:1] substrates; Carolina Soil® and vermiculite [2:1] + drainage; medium-grained sand; medium-grained sand + drainage; medium-grained sand and organic compost [1:1]; medium-grained sand and organic compost [1:1] + drainage; and Carolina Soil® and medium-grained sand [1:1]. The highest percentage of germination was obtained with the pre-treatment by immersion in water, in the times of 10 and 30 minutes, totaling 55% of germinated seeds. Treatments with hydrochloric acid did not increase the percentage of germinated seeds, which were also close to 50%. In the test with the substrates, in Carolina Soil® there were the best rates of seedling survival after transplanting (87.5%) and seedling development performance. Treatments containing organic compost resulted in lower survival (69%) and seedling development. Seed germination and seedling development in Carolina Soil® substrate and sand proved to be an excellent alternative for the production of M. zehntneri seedlings.