and lignin, lowest for highly oxidized organic compounds such as organic acids, and for the minerals. This is the basis for short-cut methods that estimate construction costs on the basis of elemental composition or energy content. They may be less precise, but do not require extended measurements of the proximate chemical composition. Consequence of using shortcut methods is that less insight is obtained as to the underlying reasons why construction costs differ between organisms. Normal values Generally, construction costs of leaves are in the order of 1.3 – 1.7 g g−1, with slightly lower values for stems and roots. The reason for this is that across most vegetative plant tissue there is a strong negative correlation between the level of – expensive - protein and the level of – expensive- lignin, and a strong positive correlation between protein and the concentration of – cheap - minerals. Seeds and fruits may have very high concentrations of sugars, or of protein, and/or lipids, and therefore show a much wider range in construction costs (1.1 - 2.3 g g−1). Payback time of leaves vary from a few days for fast-growing herbaceous species under optimal conditions, to three months or more for plants growing in low-light environments. Environmental effects Although concentrations of chemical constituents change with the environment, the effects on leaf chemical composition are general small. Leaves of plants grown at elevated may have a few percent higher construction costs, as do leaves that have been growing at higher light intensities. Functional groups Differences in leaf construction costs between deciduous and evergreen species are small, and so are the differences between inherently fast- and slow-growing herbaceous species. References Plant ecology Glucose Biomass