The ratio of the error resulting from a best-fit circle to the area of the leaf. Error is the average magnitude of residuals (Res) along the leaf's perimeter, divided by the radius of the circle. Smaller values indicate that the leaf is more circular.
The youngest, fully developed leaf from the primary stem was collected at anthesis and scanned on a flatbed scanner, at a resolution of 300 dpi. A size and colour standard was included in each picture. For morphometric measurements, colours were inverted in Adobe Photoshop to increase contrast. Images were analyed using Tomato Analyzer (Rodrigues. et al. 2010); leaf boundaries were manually adjusted when necessary.