Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2000
Publication Date: 6/1/2000
Citation: Scagel, C.F., Linderman, R.G. 2000. Changes in root iaa content and growth of bareroot conifers treated with plant growth regulating substances at planting. Journal of Environmental Horticulture. 18:99-107.
Interpretive Summary: Efficient initiation and growth of roots after transplanting can increase plant survival and decrease production costs of woody ornamental and nursery crops. Understanding how to maintain optimal conditions for the initiation and growth of roots can increase the efficiency of nutrient and water uptake during plant production and allow plants to tolerate more stressful environmental conditions. Our study showed that application of different plant growth regulators (PGRs) or alginate to the roots of bareroot Larix occidentalis, Picea englemannii, Pinus contorta, or Pseudotsuga menzesii modifies root hormone concentrations, root growth, and aboveground growth of bareroot conifers. Although changes in root growth and aboveground growth resulting from the different treatments were specific to the conifer species, PGR materials that stimulated increases in root IAA concentration generally provided the best stimulation of plant growth. We also found that application of a moisture retention gel to roots can increase root growth although by mechanisms associated with changes in root IAA levels. We believe that application of PGRs to roots of conifers as a cultural strategy to increase root growth and plant quality has the potential to be a cost-beneficial method for decreasing losses from the root damage and stress associated with transplanting.
Technical Abstract: Growth and survival of bareroot plants after transplanting is partially a function of the plant's capacity to produce new roots. We conducted an experiment to determine whether application of plant growth regulators (PGRs) or moisture retention materials could modify IAA concentration in roots, new root growth, and aboveground plant growth. We treated bareroot western larch, Englemann spruce, lodgepole pine, and Douglas-fir with Stimroot, Ethrel, Hormogel, or Alginate immediately before planting into a raised bed in a greenhouse. All treatments increased IAA content in roots of western larch, lodgepole pine, and Douglas-fir, but only Hormogel treatment increased height growth of Englemann spruce. All treatments increased stem diameter growth of western larch, Stimroot increased stem diameter growth rate of Englemann spruce and Douglas-fir, but no treatment influenced stem diameter growth of lodgepole pine. Our results suggest that application of PGRs or other root-promoting materials to the roots of bareroot conifers before planting has the potential to be a cost-beneficial method for increasing root growth and decreasing transplant shock.