DIFFERENTIAL CHEMICAL ALLOCATION AND PLANT ADAPTATION - A PY-MS STUDYOF 24 SPECIES DIFFERING IN RELATIVE GROWTH-RATE

The chemical composition of leaves of 24 wild species differing in pot ential relative growth rate (RGR) was analysed by pyrolysis-mass spect rometry. The variation in RGR significantly correlated with difference s in chemical composition: slow-growing species were richer in glucan- based polysaccharides and in C16:0 fatty acid, whereas fast growing on es contained more protein (other than those incorporated in cell walls ) and chlorophyll, sterols and diglycerides. Other, apparently signifi cant correlations, e.g. for pentose-based hemicellulose and for guaiac yl lignin appeared solely based on a group separation between mono- an d dicotyledonous species. Considering the eleven monocotyledonous and thirteen dicotyledonous species separately, correlations were found in addition to the previously mentioned general ones. Within the group o f the monocotyledons the low-RGR species were significantly enriched i n pentose-based hemicellulose, ferulic acid and (hydroxy)proline-rich cell wall protein and nearly significant in guaiacyl and syringyl lign in, fast-growing species contained more potassium. Within the group of the dicotyledons slow-growing species were enriched in triterpenes an d aliphatic wax esters. In general, the monocotyledons contained more cell wall material such as pentose-based hemicellulose, ferulic acid, glucans (including cellulose) and guaiacyl-lignin, and also more aliph atic wax esters, than the dicotyledons. The dicotyledons, on the other hand, contained somewhat more protein than the grasses.Per unit weigh t of cell wall, the amount of (hydroxy)proline- rich protein in low-RG R species was comparatively low. A higher investment of cell wall prot eins to explain the low rate of photosynthesis per unit of leaf nitrog en of slow-growing species as suggested by Lambers and Poorter (1992), therefore, seems unlikely.