RESPONSES OF POPULATIONS OF SOLIDAGO SEMPERVIRENS (COMPOSITAE) TO SALT SPRAY ACROSS A BARRIER BEACH

The responses of four populations of Solidago sempervirens to salt spray at Island Beach State Park, a barrier beach in Ocean County, New Jersey, were examined under both field and greenhouse conditions. At increasing distances from the ocean, these populations were Primary Dune (PD), Dune Hollow (DH), Intermediate (INT), and Bayshore (BAY). Salt deposition on cheesecloth traps was found to drop significantly from PD to BAY. Population responses to the salt spray gradient were monitored by examining leaf stomatal and trichome densities, leaf thickness, and the salt spray tolerance of genotypes established in the greenhouse. No significant differences in either stomatal or trichome density were found among populations in the field. Leaf thickness of field plants at the PD site was significantly greater than the DH, INT, or BAY plants: however, unsprayed plants of these populations in the greenhouse did not vary significantly in leaf thickness, and for sprayed plants, leaf thickness varied only in relation to intensity of salt application. Thus, the differences in leaf thickness of field populations were not genetically based. Both nonexpanded and fully expanded leaves of BAY plants consistently showed the greatest percentage leaf damage following both low- and high-intensity artificial salt spray, indicating possible selection for population differences in salt spray tolerance.