Insumos tecnológicos em sementes florestais para uso em restauração via semeadura direta

Abstract

Direct seeding is a technique that involves the use of seeds instead of seedlings, considered as a potential alternative for forest restoration. However, its efficiency is linked to species selection, seed quality and establishment. To contribute to the practice, were carried out in field and laboratory experiments with the following objectives: a) to test if germination in the laboratory can predict germinability and emergence (seedling density) in the field; b) evaluate the efficiency of a growth regulator in removing dormancy in seeds; c) assess whether the use of growth regulators and osmoconditioning enhance the results in the field; d) select species with better field behavior to be indicated in direct seeding. The seeds were prepared in the laboratory by carrying out germination tests, then, in the field, five randomized blocks were installed and monitored up to 720 days with the following treatments:T1 - use of growth regulator; T2 - osmoconditioning (in five species); T3 - control (with removal of dormancy in all dormant species) and T4 - use of growth regulator + osmoconditioning (polyethylene glycol -0.5Mpa) and in the case of dormant seeds, no dormancy removal was performed. Of the 38 species sown in the field, 23 emerged, corresponding to 60.5%. These were represented by 10 families, 52.2% from Fabaceae (n = 12). For dormant seeds, the use of growth regulator associated with dormancy removal was equivalent to the control, while the product applied to seeds without dormancy removal had a greater number of emerging plants. For non-dormant seeds (do not need dormancy removal) the use of the growth regulator delayed and reduced the number of emerging seeds up to 720 days after sowing, in comparison with the control. Germination showed low correlation with germinability (% emergence in relation to the number of sown seeds) and emergence (maximum number of emerging plants) in the field, in all treatments used, except for the species Handroanthus heptaphyllus, Enterolobium contortisiliquum, Poecilanthe parviflora, Pterocarpus violaceus, Platypodium elegans and Hymenaea courbaril, all with medium and large size seeds. This shows how efficient these species are in direct seeding and therefore are recommended for restoration using this technique. The osmoconditioning was not efficient in any of the species analyzed in the evaluated water potential. The growth regulator can be used to remove dormancy in field conditions.