Improving estimates of individual leaf area of sunflower

Simple, accurate, and nondestructive methods of determining leaf area of pl ants are important for many experimental comparisons, Determining individua l leaf area (LA) of sunflower (Helianthus annuus L.) can involve measuring leaf length (L) and breadth (B). The objectives of this held study were to compare published and new models to determine the most precise model to pre dict the area of individual leaves of sunflower plants and to test the appl icability of these models between sowing times, with three genotypes differ ing in maturity and stature; and at different times during crop growth. The best model, which included both the L and B factors (LA = at. + dL + eLB c), accommodated changing leaf shape during crop development. The relation ship between leaf dimensions and LA was significantly improved when sowing time and the times of leaf sampling were included in the relationship; howe ver, no significant differences were found among genotypes. The relative in crease in precision with more complex models was considered. Both length an d breadth measurements were needed to attain precision for all leaf sizes, and given the availability of computer-based statistical packages, the use of relatively complex models in the assessment of individual leaf areas wou ld appear to be a practical option.