Variability of diffusive leaf resistance and transpiration rates of various potato genotypes and its possible contribution to water economy

Diffusive leaf resistance and transpiration rate were assessed in various potato genotypes including S. tuberosum cvs. Atlantic, Cara, Alpha and Desiree, S. phureja clone PP5, a hybrid of Atlantic X PP5, and two anther-derived tetraploids of PP5. Resistance and transpiration were assessed with an LI-1600 steady state porometer on well-watered plants and differences in leaf resistance and transpiration rate among genotypes were obtained. These results imply that water economy may be improved by genotypes exhibiting small water losses. Transpiration rates calculated by dividing the weight of water transpirted per second by the area of the plant's leaflets, were lower than transpiration rates of young expanding leaflets assessed with the porometer. Nevertheless, the relative differences among genotypes were evident and a similar relationship among genotypes was maintained in the two measures. Cv. Alpha had lower transpiration rates, compared to Cara and Desiree, corresponding with its greater stomatal resistance.