ABSTRACT
Grápia (Apuleia leiocarpa Vog. Macbride) is an important native forest species that has been in an extinction process. In previous studies with young plants of grápia, visual Fe-deficiency symptoms in new leaves were related with increasing P fertilization. The aim of this study was to characterize the effects of the interaction between P and Fe fertilization on nutritional balance and growth of young plants of grápia cultivated in a Paleaudalf soil, under glasshouse conditions. The treatments consisted of a bifactorial scheme (2x3), represented by the combination of two levels of P fertilization (60 and 180 mg kg-1) and three levels of Fe (0, 6, and 12 mg kg-1); in addition a supplementary fertilization of N, K, Ca and Mg were carried out for all treatments. The plant growth was analysed monthly through plant height, stem diametrer, and number of leaves measurement. After 150 days of seedling emergence, the dry weight of roots, stem, leaves, and the whole plant, length of the root system, specific root length, number of abscissed leaves, root/shoot dry weight ratio, and P, Fe, Cu and Zn contents in plant tissue were analyzed. The ratio of P/Fe, P/Cu, and P/Zn was more suitable to evaluate the nutritional status of young plants than the analysis of the absolute content of those nutrients in the tissues. High P availability in soil caused Fe, Cu and Zn deficiency in plants of grápia. Increasing the availability of Fe, due to Fe fertilization, or by decreasing of soil pH, induced by fertilization of several nutrients, caused decreasing on Cu and Zn content in roots. In the presence of 180 mg of P kg-1 of soil, the addition of 12 mg of Fe kg-1 of soil, as Fe-EDTA, decreased leaf chlorosis and increased the growth of young plants of grápia.
Key words:
grápia; phosphorus; iron; copper; zinc