Eficiência do boro sobre o crescimento, composição mineral e variáveis fisiológicas em mudas cítricas

Abstract

Boron deficiency in citrus limits the growth of leaves and roots, due to the interruption of cell division. Moreover, the toxicity of boron decreases the plant growth, increasing the period of formation of seedlings and loss of quality. In this sense, the aim of this experimente was to evaluate the effect of borated fertilization on growth, mineral composition and physiological variables in citrus seedlings. In chapter I, it was evaluated the growth of three scions (‘Ponkan’and ‘Mexerica’ tangerine, and ‘Bahia’ orange) citrus grown in vermiculite and fertilized with boron (0, 0.5; 2.5; 5.0 mg L-1), verifying that the greater height of seedlings of ‘Mexerica’ tangerine was obtained at doses greater than 2,0 mg L-1. It was found that the diameter and the other variables were not influenced by boron. In chapter II, it was evaluated foliar concentrations of macro and micronutrients of citrus seedlings grown in vermiculite and fertilized with boron. Except for N, all other macronutrients showed inadequate foliar concentration for citrus culture. In chapter III, it was evaluated the effects of borated fertilization on the physiological variables of citrus seedlings. It was found that the transpiration of ‘Ponkan’ tangerine seedlings increased, and photosynthetic rate of ‘Mexerica’ tangerine seedlings decreased. Doses above 2.6 mg L-1 reduced the chlorophyll content of ‘Ponkan’ and ‘Mexerica’ tangerine.