Description of the growth of pequi fruits by nonlinear models

Abstract

Pequi tree is a species native to the Brazilian cerrado, with wide geographic distribution, whose fruit is very appreciated in cooking, composing traditional dishes. In general, pequi fruit is consumed when ripe in the fresh form or in the various derived products such as oils, liqueurs, sweets, ice creams among others, involving important socioeconomic activity generating employment and income in family agriculture. The aim of this study was to evaluate the adjustment of Brody, Gompertz, Logistic and Von Bertalanffy models in the growth and development of pequi fruits based on their physical characteristics such as longitudinal and cross-sectional diameter and fresh mass obtained over time. Parameters were estimated using R software routines, using the least squares method and the Gauss-Newton iterative process. The adjustment of models was compared using the following criteria: residual standard deviation, adjusted determination coefficient and corrected Akaike information criterion. In general, data presented no correlation error structure and the Von Bertalanffy model did not fit fresh mass data. The models presented good quality in the adjustment to pequi growth data, except for the Brody model for fresh mass. The Gompertz and Logistic models were those that best described variables, and the Gompertz model was the most suitable to describe diameter and mass data. Based on the adjustment, a slow initial growth was observed up to about 20 days after anthesis; after this period, the fruit developed more rapidly up to 90 days and then presented a tendency to stability until the end of the evaluation period at 117 days after anthesis, with sigmoid curve character. Pequi fruits obtained final average value of 7.1 cm for cross-sectional diameter, 6.8 cm for longitudinal diameter and 113g for fresh mass.