Mathematical characterization of maize canopies

Abstract

Leaf area and its distribution in space largely determine canopy photosynthesis and dry matter accumulation. Methods were developed to characterize the morphology of maize plants in order to calculate leaf area and leaf angle distributions. Plants were placed against a grid where ligule heights and leaf curvature characteristics were measured. Leaf widths were then measured every 10 cm along the length of the leaf. The curvature of each leaf was characterized by a general quadratic equation expressed in terms of the initial leaf angle, the coordinates of the maximum height of the leaf and the coordinates of the leaf tip. A third order polynomial, expressed in terms of leaf width at the ligule, the length of the leaf and two empirical shape coefficients, was used to describe leaf shape. From these equations leaf areas were calculated as a function of plant height and distance between rows. Leaf angle distributions were also calculated. In order to reduce the number of coefficients needed to describe a canopy, the various parameters involved with leaf curvature and shape and internode length were fitted by least squares to second order polynomial functions of leaf number. These second order polynomial functions were used to generate leaf area and angle distributions which compared favourably with the original measurements.