RELATIONSHIPS BETWEEN SPECIFIC LEAF WEIGHT AND MINERAL CONCENTRATION AMONG GENOTYPES

Physiological functions are usually expressed on a leaf area basis, wh ereas leaf mineral concentrations are often expressed on a dry matter basis. If specific leaf weight (SLW; g DM m(-2) leaf) differs among ge notypes then variability in mineral concentration may depend on the ba sis of expression. Data from experiments with peanut (Arachis hypogaea L.) and pearl miller [Pennisetum glaucum (L.) R. Br.] lines and from the literature were used to examine relationships between leaf mineral concentration and SLW. Peanut and pearl millet were grown in pots in the greenhouse in soil and solution cultures. Specific leaf weight and ash and mineral concentrations were determined at the end of the expe riments. Leaf ash concentration on a dry matter basis was negatively c orrelated with SLW and the correlation coefficients were significant i n six of nine comparisons for the two species; r = -0.65 to -0.93. In the one peanut experiment in which mineral elements were determined, t he correlations with ash were due mainly to correlations with Ca and M g, while in pearl millet, correlations were due mainly to K. The slope of a plot of leaf constituents per unit of leaf area against SLW for a range of lines is a measure of the contribution of that leaf constit uent to increased SLW. From data in the literature it appears that inc reased SLW is due mostly to the increase of cell wall components and n onstructural carbohydrates, and sometimes protein. Leaf mineral per un it of leaf area appears to be unrelated or only slightly increased wit h increased SLW and thus declines on a unit weight basis because of di lution by increased cell wall content or soluble carbohydrate. (C) 199 6 Elsevier Science B.V.