Effect of elevated atmospheric CO 2 on growth, photosynthesis and water relations of salt marsh grass species

Abstract

The C 3 grass species Scirpus maritimus L. and Puccinellia maritima (Huds.) Parl., and the C 4 grass species Spartina anglica C.E. Hubbard and Spartina patens (Ait.) Muhl. were grown at ambient (340 p.p.m. CO 2) and elevated (580 p.p.m. CO 2) atmospheric CO 2 concentration, at low (10 mM NaCl) and high salinity (250 mM NaCl) under aerated and anaerobic conditions in the culture solution. The relative growth rate of both the C 3 grass species was enhanced with atmospheric CO 2 enrichment, no such increase was found in the C 4 grass species. High salinity reduced growth of the C 3 species tested, but this relative growth reduction was not prevented by elevated CO 2 concentration. The growth increase at elevated CO 2 of Scirpus maritimus and Puccinellia maritima is greater under aerated than under anaerobic solution conditions. Water-use efficiency of all species was increased by elevated CO 2. In the case of Scirpus (C 3), this increase was caused by increased net photosynthesis, for Spartina patens (C 4) photosynthesis was not increased, but transpiration was reduced. The water potential of the shoot was less negative under conditions of CO 2 enrichment, in particular at increased salinity (250 mM NaCl).