Qualidade de diásporos e crescimento de mudas de Myrocarpus frondosus allemão no viveiro e no campo

Abstract

Myrocarpus frondosus (cabreúva) belongs to the Fabaceae family and is a native species of wood, ecological, ornamental and medicinal interest. However, despite the importance of this species, there is still a lack of studies on seed technology, seedling production and field growth. In this sense, this study was divided into four chapters. In Chapter I the quality and storage of diaspores in different environments were evaluated. The batch consisted of diaspores collected in the municipality of Nova Palma, RS and evaluated for the weight of one thousand seeds, degree of humidity, electrical conductivity, germination test and sanity test. In the germination of diaspores of Myrocarpus frondosus the substrate between sand and vermiculite is recommended. In the sanity test the main genera associated to the diaspores stored were Fusarium, Aspergillus, Alternaria, Colletotrichum, Penicillium, Rizopus, Cladosporium and Mucor. Samples from the same batch were stored in different environments, with the dry and cold room (18°C and 49% RH) being considered the best environment for conservation for 360 days. The species demonstrates intermediate storage behavior. In Chapter II, the quality of seedlings in the nursery was evaluated in order to indicate the adequate substrate and fertilization to the production of seedlings. Four combinations of substrates and four fertilizations were evaluated through the analysis of the morphological attributes: height (H), stem diameter (SD), H/SD ratio, leaf area, root length, aerial dry mass, root dry mass, total dry mass and Dickson quality index, and physiological attributes: chlorophyll a, chlorophyll b, carotenoids, initial fluorescence, maximum fluorescence, maximum photochemical efficiency of photosystem II - Fv/Fm and electron transport rate. The use of the Sphagnum peat-based substrate (40%) with carbonated rice husk (60%) associated with the 6 g L-1 dose of controlled release fertilizer is recommended, as they generally present the best results for the morphological and physiological variables in the nursery. In Chapter III the objective was to evaluate the growth of seedlings in the nursery under different shadings. The treatments used were full sun (0%) and three shade intensities (30, 50 and 70%). Myrocarpus frondosus requires shading in the early stages of growth, with shading of 50 and 70% being an adequate alternative for seedling production. In Chapter IV the objective was to evaluate the survival and initial growth of seedlings under different levels of shading in the field. The treatments were: 0% (full sun), 18, 50 and 70%. The use of shading in the planting influences the survival and morphological and physiological attributes of the species, confirming that the species maintains the pattern obtained in the nursery, since it requires shading from 50 to 70% in its initial stage of growth in the field (540 days after planting). The species can be used in plantations for sub-forest enrichment and in consortium with other fast-growing species capable of shading the cabreúva plants.