Allometric modelling to estimate the leaf area of purslane (Portulaca umbraticola Kunth.)

Abstract

Portulaca umbraticola is a species that has several uses, including ornamental. Among the variables measured in ornamental plants are the biometric data of the leaves, which can be obtained through image analysis, using indirect method, which is simple, accurate and economically viable. This work aimed to propose equations obtained by mathematical models to estimate the leaf area of P. umbraticola. The study was conducted at the Universidade Federal Rural do Semi-Árido, Mossoró, RN, Brazil. Three hundred leaves of each of the five genotypes of P. umbraticola were evaluated for length, width, product between length and width, and leaf area. Determination and correlation coefficients, Akaike information criterion, Willmott agreement index, coefficient of variation, normality using the Shapiro-Wilk test, principal components and Student's t-test were used to systematize the data. Descriptive measurements obtained from the leaf blades of P. umbraticola showed variability between genotypes, demonstrating that the sample was representative for the population analyzed. The regression models obtained were linear and potential. Allometric equations can be used to estimate leaf area in P. umbraticola, and the recommended equations are ŷ = 0.356*L (R² = 0.91) for length, ŷ = 1.665*W (R² = 0.90) for width and ŷ = 0.016 × 0.0711*LW (R² = 0.99), ŷ = 0.715*LW (R² = 0.99) and ŷ = 0.724*LW (R² = 0.99) for the relationship between leaf length and width. The equations to estimate the leaf area of P. umbraticola showed excellent data fits, with values of R² = 0.993 and little dispersion of the data.