Leaf water relations and assimilation in Scurrula yadoriki and its host species

Abstract

This study was conducted on Scurrula yadoriki (Sieb.) Danser and its host trees to examine leaf water potential and leaf water relations using the pressure-volume technique. Compared to the various hosts, S. yadoriki had more negative leaf water potentials, suggesting water flow toward the parasite from the host. There was no significant difference in photosynthetic rates between S. yadoriki and Machilus thunbergii or Acer amoenum. However, the parasite exhibited substantially higher daytime transpiration rate than the host trees. These results suggest that the parasite was able to obtain sufficient water and nutrients from host species because the lower leaf water potential at midday enabled it to maintain photosynthetic activity and growth. Leaves of the parasite also maintained a higher turgor pressure than host trees, suggesting that this parasite has a competitive advantage in the acquisition of water from the host species.