Do desiccation tolerances control the vertical distribution of intertidal seagrasses?

Photosynthetic processes in Zostera japonica, an upper intertidal species, were found to be more severely affected by desiccation than Z. marina, a lower intertidal and subtidal species, at comparable levels of tissue water content. The data indicate that photosynthetic responses to desiccation at the level of the individual leaf are insufficient to explain observed patterns of intertidal seagrass zonation. Desiccation tolerance in seagrasses is more likely to involve a complex interaction of morphological traits and growth strategies at the level of the whole plant, such as downsizing (e.g. smaller, narrower leaves), reduced structural rigidity and increased rates of leaf abscission and leaf turnover.