Transplanted red oak seedlings mediate transplant shock by reducing leaf surface area and altering carbon allocation
One-year-old red oak seedlings (Quercusrubra L.) from three open-pollinated families were produced in 1 m tall containers during 1989. In spring 1990, the seedlings were either transplanted (which included pruning the main root to a 15-cm length) or not. Transplanted seedlings either received a 5-s basal dip in 20 mM indole-3-butyric acid or did not. The seedlings were placed in a greenhouse and harvested at the beginning of the first lag phase, at the beginning of elongation of the second growth flush, and 70 days after the beginning of the experiment. Root-pruning removed 42 to 50% of whole-plant dry weight. Transplanted seedlings had significantly reduced leaf surface area and began a second growth flush later than untransplanted seedlings. There were no treatment differences in CO2 assimilation rate on a per unit leaf surface area. Predawn xylem water potential in transplanted seedlings was lower than in untransplanted seedlings. Transplanted seedlings used less root and more shoot reserves to develop the first flush than untransplanted seedlings. Treating root-pruned seedlings with 20 mM indole-3-butyric acid did not significantly increase growth potential compared with untreated transplanted seedlings. For transplanted red oak, transplant shock seems to be mediated through reduced leaf surface area, which reduces whole-plant water use.