Mg and pH effect on reducing Al toxicity in banana plants grown in hydroponic solution

Abstract

A hydroponic experiment was carried out with the objective of studying the effect of Al toxicity on the growth and absorption of water and nutrients by banana plants, and the effect of Mg and pH on Al toxicity. The six treatments evaluated consisted of the combination of four Mg rates (25, 50, 100, 200 mg l-1) and two Al rates (0 y 25 mg.l-1) at 3 pH values which produced the following treatments: 1) 25-0 pH 4; 2) 25-25 pH 3; 3) 50-25 pH 3; 4) 100-25 pH 3; 5) 200-25 pH 3; and 6) 25-25 pH 5. Tissue culture plants of the Grand Naine clone between 7 and 10 cm height were grown in 20 L containers for 63 days. At the end of this time, plant height, pseudostem circumference, plant biomass, leaf emission rate, leaf area and nutrient absorption were measured. Al reduced the magnitude of all the growth variables, except leaf emission rate. The Mg rate of 50 mg l-1 partially reduced the effects of Al on plant height and pseudostem circumference. Greater concentrations of Mg gave similar results to those of Mg at 25 mg l-1. Aluminum affected biomass production principally that of the first order roots, the effect being partially reduced by the increment of Mg concentration in the solution. Water absorption significantly decreased by Al, while the 50 mg l-1 Mg rate also tended to decreased water uptake. Increasing pH from 3 to 5reduced Al toxicity. Aluminum reduced biomass production by 65 % compared to plants with no Al, while the total absorption of macronutrients decreased between 56 and 89 % in the following order Mg≥Ca>S>N≥K>P and micronutrients order of concentration reduction was Fe>Mn>Zn>Cu=B for the micronutrients.