Abstract
The leaf has a vital role in the functions of the plant, being responsible for photosynthesis and gas exchange. Thus, the objective of this study was to fit a mathematical equation model to estimate the leaf area of Maytenus obtusifolia Mart. through the linear dimensions of the leaves. For that, six hundred and fifteen healthy leaves were collected from plants belonging to the Federal University of Espirito Santo, Sao Mateus Campus, in the municipality of Sao Mateus, located in the north of the State of Espirito Santo, Brazil. All leaves were digitized and the images processed using the ImageJ® software, obtaining the measurements of the maximum length of the main midrib (L), the maximum width of the leaf blade (W) and the real leaf area (RLA) of each sheet. Subsequently, the product of length and width multiplication (LW) was also obtained. 500 sheets were randomly separated for the generation of models of mathematical equations and their respective coefficient of determination (R2), where RLA was used as dependent variable as function of L, W or LW as independent variable. Based on the models generated, a 115 leaf sample was used for validation, where the L, W and LW values of this sample were replaced in the adjusted equations, thus obtaining the estimated leaf area (ELA). A comparison of the means of RLA and ELA was performed by Student’s t test at 5% probability. We also calculated the mean absolute error (MAE), the root mean square error (RMSE) and the Willmott index (d). The best equation was defined by the following criteria: non-significant values of RLA and ELA averages, R2 and index d closest to unit, and MAE and RMSE values with greater proximity to zero. The quadratic model equation represented by ELA=0.18122798+0.72847767(LW)+0.00002789(LW)2 generated by multiplying the length with the width (LW) is the most suitable for the estimation of the leaf area of Maytenus obtusifolia Mart., in a fast, safe and non-destructive way.
Highlights
The leaf is the organ that performs vital functions, being responsible for carrying out the photosynthesis and the gas exchanges of the plant
The product of length and width multiplication (LW) was obtained. 500 sheets were randomly separated for the generation of models of mathematical equations and their respective coefficient of determination (R2), where real leaf area (RLA) was used as dependent variable as function of L, W or LW as independent variable
Based on the models generated, a 115 leaf sample was used for validation, where the L, W and LW values of this sample were replaced in the adjusted equations, obtaining the estimated leaf area (ELA)
Summary
The leaf is the organ that performs vital functions, being responsible for carrying out the photosynthesis and the gas exchanges of the plant. For this reason, the determination of leaf area and fundamental in ecological, agronomic and ecophysiological studies may be essential in the understanding of the behavior of plants in relation to light interception, photosynthetic efficiency, evapotranspiration and responses to the use of irrigation and fertilizers, directly influencing the growth and development [1] [2]. The indirect methods allow a precise and fast estimate of the leaf area, without the need of leaf destruction, and can be used throughout the crop cycle, being possible the successive measurements in the same plant [3]. Notorious are the studies that seek the adjustment of mathematical equations that estimates the leaf area of various crops through the linear dimensions of its leaves as reported by several authors Cucumis sativus L. [4], Vicia faba L. [5], Helianthus annuus L. [6], Crambe abyssinica [7], Jatropha curcas [8], Coffea canephora [9], Vitis vinífera L. [10], Rosa hybrida L. [11], Crotalaria juncea [12], Litchi chinensis Sonn. [13], Ormosia paraensis Ducke [2], guava [14], Artocarpus heterophyllus [15] and Plectranthus barbatus Andrews [16]
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