Abstract
To determine the extent of physiological integration in the clonal herb Lycopodium flabelliforme, the survivorship and water relations of severed and connected ramets were compared. In the field, severed ramets experienced 50% greater mortality than intact ramets. In greenhouse experiments, the xylem pressure potentials of severed ramets exposed to 200 μmol°m—2°s—1 of photosynthetically active radiation were as much as 1.3 MPa lower than the xylem pressure potentials of intact illuminated ramets connected to shaded ramets. Thus, a water potential gradient develops within the xylem and facilitates water movement between shaded ramets and connected, illuminated ramets. Measurements of root distribution and capacitance supported this conclusion. Although each ramet did not necessarily have an associated root, water storage was greatest in roots and in ramet crowns, suggesting that irritated ramets lacking nearby roots must rely on other ramets for water. Physiological integration of L. flabelliforme ramets facilitates water movement in the xylem, which may moderate the effects of environmental variability on ramet water potential.
Published Version
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