Central composite design-based analysis of specific leaf area and related agronomic factors in cultivars of rapeseed (Brassica napus L.)

Specific leaf area (SLA) is an important parameter in evaluating leaf function, yield potential, and ecological adaptability. Data from our field experiments from 2000 to 2005 were used to evaluate the values of SLA and related agronomic factors. SLA remained stable during winter, differed significantly among the dates of observation, and declined from seedlings to maturation in all the cultivars tested. ANOVA analysis showed that SLA differed significantly with sowing date but not with the cultivar, and was correlated positively with population density but negatively with the weight of leaves, roots, and the stem and with potassium application. A parabolic relationship was found between SLA and application of phosphorus. SLA at different observation dates before anthesis was negatively correlated with shoot weight at anthesis. An appropriate combination of population density and application of phosphorus and potassium could be helpful in securing desirable values of SLA (high at the seedling stage and low from the middle growth stage to maturity) and optimal population morphogenesis and, in turn, high yields.