ABSTRACT The interception of photosynthetically active radiation (PAR) is a key factor for biological productivity, and its magnitude depends on the availability of solar radiation, the stage of the plant development cycle, and the arrangement of plant structures. Given the arrangement of the vegetative and reproductive structures in different portions in the canola canopy, the objetive of the study was to morphologically characterize canola cultivars and establish relationships with the stratification of the efficiency of PAR intercep tion. Eight canola cultivars were evaluated in regards to PAR and plant morphological traits. Following the analysis of variance, treatment means were grouped, and the phenotypic correlation matrix between the traits was determined. We observed a strong relationship between the PAR interception efficiency of vegetative and reproductive structures with morphological traits. Plants with a higher number of branches have more siliques and greater efficiency of PAR interception, mainly through the reproductive structures. The characterization of morphological differences between canola cultivars in the PAR interception efficiency should be performed by measures stratified by vegetative and reproductive structures.

RESUMEN La interceptación de radiación fotosintéticamente activa (ARF) es importante para la productividad biológica y su magnitud depende de la disponibilidad de radiación solar, la etapa del ciclo de desarrollo de la planta y la disposición de las estructuras de la planta. Dada la disposición de las estructuras vegetativas y reproductivas de la canola en diferentes porciones del perfil del dosel de las plantas, el objetivo del trabajo fue buscar la caracterización morfológica de cultivares de canola y establecer relaciones con la estratificación de la eficiencia de interceptación de la radiación fotosintéticamente activa. Se evaluaron ocho cultivares de canola, se midió la ARF y se evaluaron los caracteres morfológicos de la planta. Se realizaron análisis de varianza, agrupamiento de medias y se determinó la matriz de correlación fenotípica entre los caracteres. Se observó una alta relación entre la eficiencia de interceptación de la RFA de estructuras vegetativas y reproductivas con caracteres morfológicos. Las plantas con mayor número de ramas tienen más sílice y mayor eficiencia en la interceptación de la radiación fotosintéticamente activa, principalmente debido a las estructuras reproductivas. La caracterización de las diferencias morfológicas entre cultivares de canola en la eficiencia de interceptación de la RFA debe realizarse mediante medidas estratificadas por estructuras vegetativas y reproductivas.

RESUMO A folha é uma estrutura de grande importância para as plantas, visto que por meio dela ocorrem as trocas gasosas e a transformação da energia luminosa em energia química. O objetivo neste trabalho foi gerar e testar modelos matemáticos para a estimativa de área foliar de folhas de canola em função das dimensões foliares. Para isto foram realizados dois experimentos com canola no ano de 2014 e coletadas folhas em diferentes estágios fenológicos e de diferentes tamanhos e formas; posteriormente foram medidos o comprimento, a largura e a área foliar (com medidor automático) de 606 folhas dentre as quais 371 ovaladas e 235 lanceoladas. Os modelos foram gerados utilizando-se comprimento, largura e comprimento versus largura como variáveis independentes e a área foliar como variável dependente. Os modelos foram validados com um grupo distinto de folhas dos utilizados para a geração. Obteve-se o total de 27 modelos escolhendo-se aqueles que apresentaram as melhores estatísticas e maior simplicidade. Os modelos que podem ser utilizados para ambos os tipos de folhas e apresentam alta precisão de estimativa de área foliar em canola, são o modelo polinomial AF = 0,88735 L2 + 0,93503 L e o modelo potencial AF = 1,1282 L1,9396.

ABSTRACT The leaf is a very important structure of the plants, since it allows gas exchanges and the transformation of light energy into chemical energy. This study aimed to generate and test mathematical models for leaf area estimation in canola based on leaf dimensions. Two experiments were conducted with canola in 2014, in which leaves were collected in different phenological stages with different sizes and shapes. Subsequently, leaf length, width and area were measured (with automatic meter) in 606 leaves, which included 371 ovate and 235 lanceolate leaves. The models were generated using length, width and length versus width as independent variables and leaf area as dependent variable. The models were validated using a group of leaves different from those used to generate the models. A total of 27 models were obtained and those with best statistics and higher simplicity were selected. The polynomial model LA = 0.88735 W2 + 0.93503 W and the power model LA = 1.1282 W1.9396 can be used for both types of leaves and have high accuracy in the estimation of canola leaf area.