Abstract
This study investigated the changes in leaf water potential (ΨL) and photosynthetic rate (Pn) of cropping and non-cropping blueberry plants grown under drought and re-watering conditions. Nine-year-old ‘Tifblue’ plants grown in a pot were used. When plants grown under drought conditions, ΨL and Pn of leaves decreased as soil water content decreased. Pn decreased to near zero when ΨL was approximately -3.5 MPa and soil water content was approximately 8%. Under that condition, all fruits and some shoots wilted and some fruits dropped. Pn of cropping plants decreased more rapidly than that of non-cropping plants, under drought conditions. After re-watering, ΨL and Pn of plants grown under drought conditions were increased and then these values reached half the level of plants grown under well-watered conditions. The rate of increase in Pn in cropping plants was slower than that in non-cropping plants under drought conditions. The values of stomatal conductance and transpiration rate showed a tendency similar to that of Pn. These results showed that the critical point of ΨL for recovering plant vigor was less than -3~-3.5 MPa. Furthermore, drought stress was promoted by fruit loading.
