Hydraulic conductance of two co-occuring neotropical understory shrubs with different habitat preferences

Whole plant hydraulic conductance was measured for two co-occuring neotropi cal rainforest understory shrub species of the genus Piper, which differ in their habitat preference with respect to soil moisture: P, trigonum is res tricted to wet habitats, whereas P. cordulatum occurs in drier sites. Plant s were grown under four treatments (two light conditions crossed with two w atering regimes), representing the extremes of conditions in their natural habitat. The data showed significantly higher total hydraulic conductance a nd leaf specific conducance in the drought-avoiding species, P. trigonum, t han in the drought-tolerant species P. cordulatum. The measured parameters also differed between growth treatments. The species differences in hydraul ic conductance could be interpreted as adaptive in the respective species' habitat, and might thus be important in determining habitat preference and distribution of the two species.