Influence of nitrogenous fertilization on the protein content of flavedo of ‘Navelina’ oranges and its relationship with rind colour

Abstract

SummaryNitrogenous fertilization effects on the protein concentration of flavedo of ‘Navelina’ oranges during ripening was studied in an experimental greenhouse, using cuttings grown in pots with inert sand and nutrient solution. Two types of nutrient solution were used: a nitrate solution (all nitrogen in nitrate form) and an ammoniacal-nitrate solution (40% nitrogen in ammonium form and 60% in nitrate form). The protein concentration of fresh flavedo of fruits irrigated with ammoniacal-nitrate solution was higher than that of fruits irrigated with nitrate solution. When the protein concentration of flavedo is high, the rind of fruits reach a yellow or orange-yellow colour earlier during development. In both types of nutrient solution, the quantity of nitrogen applied did not influence the total protein concentration of fresh flavedo nor the timing of fruit rind colour change from green to orange-yellow. After fruit set, the sooner the ammoniacal- nitrate nutrient solution was supplied, the sooner fruits reached an orange-yellow colour, and the higher was the total protein concentration of fresh flavedo, although there were no significant differences between the protein concentrations of flavedo of fruits from cuttings whose irrigation started with the ammoniacal-nitrate solution at different time. Results of this and a previous study suggest a relationship between the rind colour change and the protein concentration in the flavedo of fruit.