The root pressure and leaf transpiration are two important driving
forces for water transport in intact plants. Root pressure can be
indirectly measured by the xylem sap volume, as the xylem sap
was collected from the decapitated stem. Hence, root pressure is a
driving force for water transport (Kodur et al., 2010). In this study,
the volumes of xylem sap in the plants with cucumber roots were
similar. A similar result was also observed in plants with pumpkin
roots. However, compared with plants with cucumber roots, plants
with pumpkin roots had higher xylem sap volume (Fig. 2), suggesting
that plants with pumpkin roots had higher root pressure which
facilitate water transport in plants. Higher leaf transpiration could
also be responsible for higher water transport in the intact plants
with pumpkin roots because the gas exchange parameters were
measured from intact plants in this study. Therefore, plants with
pumpkin roots had lower xylem Na+ concentrations, which could
be also partly related to higher water transport capacity caused by
root pressure and leaf transpiration.