Influência da variedade e do porta-enxêrto, na composição mineral das fôlhas de citros

Portuguese. No presente trabalho são relatados os efeitos determinados; por diferentes combinações copa-cavalo, na composição mineral das fôlhas de citros. O material para o presente estudo foi retirado de dois ensaios de cavalos para laranja pêra e laranja baianinha (Citrus sinensis Osbeck) instalados na Estação Experimental de Limeira, do Instituto Agronômico. Amostras de fôlhas foram colhidas em diferentes estágios de crescimento e correspondentes o dois ciclos vegetativos, e a composição estudada separadamente para árvores de mesma idade. Os resultados obtidos permitiram concluir que além dos efeitos na composição das folhas devidos à variedade e ao porta-enxêrto, outros fatôres como longevidade e moléstias de vírus devem ser considerados pora o julgamento dos efeitos da adubação pela análise foliar.

English. The influence of five different combinations scion-rootstock for two scion varieties on the percentage of nitrogen, phosphorus, potassium, calcium, and magnesium in citrus leaves is reported. Leaves from fruiting shoots of two spring flushes were taken from Baianinha and Pêra oranges trees (Citrus sinensis Osbeck) on two experimental orchards located in the Experiment Station of Limeira, State of Sao Paulo. The rootstocks On which they are budded and used for this study were: Pêra orange, and sweet orange (C. sinensis Osb.), Rangour lime (C. reticulata Blanco X C- aurantifolia Swing (?)), rough lemon (C. limon Burm. f. X (?)), and Cleopatra mandarin (C. reticulata Blanco). In the spring of 1957 when the leaf sampling was started the trees on sweet orange, Rangpur lime and rough lemon rootstocks were 21 years old and those an Pêra and mandarin rootstocks 7 years old, but only plants of the same age were compared. Fertilization was uniform in all plots and the soil apparently very uniform. Confidence limits for the mean results of inorganic composition of leaves 3 to 6 months old of two flushes are presented. Seasonal changes in nutrient composition of leaves ore olso shown. The leaves of both scion varieties differed in their principal mineral constituents. The major difference was found in the potassium content. Leaves of Baianinha orange trees contained relatively more potassium than Pêra orange leaves. The composition of leaves changed according to the rootstock species. Differences in potassium, calcium, and magnesium levels in leaves of the some scion variety were found to be significant when Pêra orange and Cleopatra mandarin were the rootstocks. Variations in the composition of scion leaves in the older combinations could be associated with virus disease tolerance and longevity of species. In view of the results obtained, other factors such as virus diseases, longevity, etc. besides varietal effects and selectivity of rootstocks to absorb nutrients, must be taken into account in attempting to associate the results of foliar analysis with fertilizer utilization by citrus trees.