Changes in survival, growth and photosynthetic pigment in response to iron increase in the leaf and root-rhizome tissues of eelgrass Zostera marina

This study tested the responses of leaves and root-rhizomes of eelgrass Zostera marina plants to iron additions in a two-compartment system which allowed the separation of the root-rhizome portion from the stems and leaves. We subjected whole Z. marina plants to seawater containing 500 mu g l(-1) Fe (reference seawater) and 700 mu g l(-1) Fe in the leaf and/or root-rhizome compartments for over 30 days under controlled laboratory conditions. We measured plant response in terms of survivorship, morphology, growth and leaf pigment content. The results showed that adding Fe to the leaf compartment resulted in higher survival and stimulated both leaf and root-rhizome growth of the Z. marina plants. However, Fe addition to root-rhizome compartment only obtained higher survival and greater internode diameter and root elongation rate. Survival analysis combined with morphological and dynamic assessment suggested that both the leaves and the root-rhizome system of Z. marina have the ability to absorb iron from their environment but uptake occurs mainly in the leaves from the surrounding water. And the result also suggested that iron is mainly translocated from leaves to root-rhizomes. Furthermore, adding Fe to the leaf compartment stimulated significant increases in leaf chlorophyll contents of the Z. marina plants, is similar to those reported for other seagrass species. This study will further develop our understanding of the physiological ecology of this species and provides data that could prove helpful in the development of successful establishment of Z. marina plants.