Non-destructive models to estimate leaf area on bell pepper crop/Modelos nao-destrutivos para estimar a area foliar na cultura do pimentao

The leaf area determination are extremely important in agronomic and physiological studies, as they provide valuable information in vegetable metabolism, methods used for this purpose should be accurate. This study aimed to develop polynomial models to estimate leaf area (LA). The methods used were leaf discs and ImageJ ® software, with measures of length (L), width (W), and relationship between length times width (LW) in leaves of the bell pepper crop in two field trials with two hybrids: Arcade and Impacto, as well as, the correlation of values found when using the two methods. Through a random sampling, 560 leaves from each hybrid were selected, at different stages of crop growth. Regression analysis of LA versus measures L, W and LW were performed by linear and quadratic models. The variable that best estimated LA was the relationship between LW with linear model ([r.sup.2]=0.98). Measurements of length and width of leaves presented adjustment to quadratic model [r.sup.2]=0.93 and [r.sup.2]=0.91, respectively. The integrator model for all samples and both hybrids was: LA=0.57 x LW. The destructive method of leaf discs showed high correlation ([r.sup.2]=0.99) with the non-destructive method of ImageJ ® software. Key words: Capsicum annuum, ImageJ, leaf discs, individual leaf area, nondestructive methods. A determinacao da area foliar e importante, em estudos agronomicos e fisiologicos, para a obtencao de informacoes sobre o metabolismo vegetal e as tecnicas utilizadas devem ser simples. O objetivo deste estudo foi desenvolver modelos polinomiais para estimar a area foliar (AF). Foram utilizados os metodos de discos foliares e software ImageJ, com as medidas do comprimento (C) e da largura (L), e a relacao entre o comprimento vezes a largura (CL) em folhas da cultura do pimentao, em dois ensaios com dois hibridos, Arcade e Impacto, e correlacionar os valores encontrados pelos dois metodos. Atraves de amostragem aleatoria simples, foram selecionadas 560 folhas de cada hibrido, em diferentes estagios de crescimento da cultura. A analise de regressao da area foliar versus as medidas de C, L e CL foi realizada por modelos lineares e quadraticos. A variavel que melhor estimou a AF foi a relacao entre o CL, pelo modelo linear com [r.sup.2]=0,98. As medidas do comprimento e da largura das folhas apresentou ajustamento do modelo quadratica de [r.sup.2]=0,93 e [r.sup.2]=0,91, respectivamente. O modelo integrador de todas as amostras, para ambos os hibridos, foi: