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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #107771
Title: TEN YEAR GROWTH AND SURVIVAL OF DOUGLAS-FIR SEEDLINGS TREATED WITH PLANT GROWTH REGULATING SUBSTANCES AT TRANSPLANT

Author
item Scagel, Carolyn
item Linderman, Robert

Submitted to: Canadian Journal of Forest Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/5/2000
Publication Date: 11/1/2000
Citation: Scagel, C.F., Linderman, R.G. 2000. Ten year growth and survival of douglas-fir seedlings treated with plant growth regulating substances at transplant. Canadian Journal of Forest Research. 30:1778-1787.

Interpretive Summary: Conifer seedlings used in reforestation are often planted in extremely harsh sites. To survive, newly planted trees must generate new roots that grow into the soil in order to acquire water and nutrients. We conducted experiments to determine if application of commercially available plant growth regulators (PGRs) or moisture retention gels to roots can modify IAA Acontent in roots, root growth, and tree survival. Two different 1+0 bareroot stock types of Douglas-fir were treated with Stimroot, ethrel, alginate, or a combination of Stimroot and alginate, then planted in a clearcut. We measured new root growth and IAA concentrations in roots after planting and monitored aboveground growth and tree survival for ten growing seasons after planting. Treatment with Stimroot or the combination of alginate and Stimroot increased IAA conjugate and free IAA content of roots, root growth, and tree survival. Alginate treatment increased new root growth and survival but without any increase in free IAA content in the roots after planting. Ethrel treatment increased free IAA content and root growth but had no effect on IAA conjugate content or survival. A cost analysis of treatments suggests that PGRs or alginate can decrease the cost necessary to attain target stocking and increase tree size. Our results suggest that application of PGRs or other root-promoting materials to the roots of Douglas-fir roots before planting has the potential to be a cost-beneficial method for increasing root growth and tree survival. Although the results of this study suggest there is variability in response to PGR treatment based on plant species, stock type, and environment, we believe there is potential to fine tune PGR application concentrations and timing to reduce some of this variability.

Technical Abstract: We conducted experiments to determine if application of commercially available PGRs or moisture retention gels to roots can modify IAA content in roots, root growth responses, and tree survival. Two different 1+0 stock types (PSB313B and PSB323) of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) were treated with Stimroot, ethrel, alginate, or a combination of Stimroot and alginate, then planted in a clearcut. We measured new root growth and IAA concentrations in roots two weeks after planting and monitored aboveground growth and tree survival for ten growing seasons after planting. Although some of our PGR treatments increased root growth, not all increases in root growth were correlated to plant survival. PGR treatments that increased the free IAA content in roots, root initiation, and root growth also increased above ground growth, but only application of PGR treatments containing IBA increased survival of trees. Treatment with Stimroot or the combination of alginate and Stimroot increased IAA conjugate and free IAA content of roots, root growth, and tree survival. Alginate treatment increased new root growth and survival, but without an increase in free IAA content in the roots after planting. Ethrel treatment increased free IAA content and root growth, but had no effect on IAA conjugate content or survival. A cost analysis of treatments suggests that PGRs or alginate can decrease the cost necessary to attain target stocking and increase tree size. Our results suggest that application of PGRs or other root-promoting materials to the roots of Douglas-fir roots before planting has the potential to be a cost-beneficial method for increasing root growth and tree survival.