PLASTIC AND NONPLASTIC VARIATION IN GROWTH OF NEWLY ESTABLISHED CLONES OF SCIRPUS (BOLBOSCHOENUS) MARITIMUS L. GROWN AT DIFFERENT WATER DEPTHS

The importance of plastic responses to water depth as compared to non- plastic (developmental) changes in ramet (consisting of a culm e.g., s tem with leaves, rhizome spacers and - tuber, and roots) characteristi cs of newly established clones of the emergent macrophyte Scirpus mari timus L. was examined. Clones were established from seeds and grown in outdoor ponds at water depths of 0 (waterlogged), 10, 20, and 30 cm. Number and dry weight of ramets were higher at 0 and 10 than at 20 and 30 cm water depth. There was no plastic but a high non-plastic variat ion in rhizome spacer lengths. In response to water depth culms were l onger, but the relative length growth rate of culms and leaf morpholog y remained unaffected by water depth. Total ramet dry weight did not d iffer between water depths, but with increasing water depth the propor tional allocation of dry matter to stems increased at the expense of r oots and rhizome spacers. In sequentially produced ramets dry weight i ncreased, and the proportional dry matter investment in tubers (storag e organs) and roots increased at the expense of leaves and rhizome spa cers. Plasticity in morphology and biomass allocation of ramets was di rected towards a fast emergence from the water. However, no plasticity in ramet and tuber dry weight was apparent. Therefore, the non-plasti c rather than the plastic variation in ramet characteristics is of gre at importance for the persistence of newly established S. maritimus cl ones after drawdowns. (C) 1998 Elsevier Science B.V. All rights reserv ed.