Micronutrientes no sistema solo-Pinus caribaea Morelet em plantios apresentando amarelecimento das acículas e morte de plantas

摘要

This study was carried out to diagnose senescence and death of pine trees (Pinus caribaea Morelet), observed after yellowing and progressive necrosis of the needles in the Brazilian Savanna (Cerrado) in Western Minas Gerais, Brazil. The varieties caribaea and hondurensis, planted between 1977 and 1982 were compared. Samples from twenty trees were collected from the three sites studied; ten with yellowing of the needles and ten without symptoms. From each tree, phloem tissue and xylem from root segments and needles were collected and the contents of Fe, Mn, Zn, Cu and B were analyzed. The soil is Yellow Latosol (Typic Acrustox). Soil samples were colleced at the following depths: 0-5, 5-10, 10-20, 20-40, 40-60, 60-80, 80-100, 100-150, 150200, 200-250 and 250-300 cm. Soil analysis was performed to evaluate the contents of Fe, Mn, Zn, Cu and B concentrations. The mean Fe, Zn, Cu and B concentrations did not differ significantly in the green and yellowed needles but the Mn contents were significantly lower in the yellowed needles. Visual symptoms and laboratory test revealed a complex Mn deficiency.