Root Regeneration in Transplanted Deciduous Nursery Stock

Abstract

Root systems of coarse-rooted species regenerate primarily via adventitious means after transplanting, whereas initial root regeneration of fibrous-rooted species is from elongaton of existing roots and secondarily from adventitious regeneration. Fibrous-rooted species transplant more easily than coarse-rooted species because they have rapidly regenerating intact root tips when planted. Also, they tend to regenerate more adventitious roots faster. Budbreak occurs before root regeneration in dormant-transplanted stock. A contributing factor to this sequence of events is cool spring soils with root regeneration being inhibited below 10C. Transplant shock is minimized by decreasing the time between budbreak and first-froot regeneration. Auxin (IBA) applications promote root regeneration by increasing the number of roots regenerated. In recurrently flushing species, such as red oak, effects of IBA treatments are not expressed in the first flush because shoot elongation and leaf expansion are completed before root regeneration occurs. IBA treatment effects are, however, expressed in the second growth flush–IBA-treated plants develop more leaf area (through a combination of increased numbers of leaves and increased leaf size) than untreated seedlings. Relative growth rates for both IBA-treated and untreated seedlings were higher during the period between budbreak and first root regeneration than after root regeneration. IBA-treated seedlings have higher RGR for the period between first root regeneration and the end of the growing season than do untreated seedlings. However, transplanted red oak have significantly lower season-long RGR than do untransplanted seedlings. The cause of high RGR for the period between budbreak and first root regeneration is unknown.