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  • Author or Editor: W. Todd Watson x
  • HortTechnology x
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Studies have demonstrated that the size of transplanted trees has a measurable impact on establishment rates in the landscape. Larger trees require a longer period of time than smaller trees to produce a root system comparable in spatial distribution to similar sized non-transplanted trees. This lag in redevelopment of root system architecture results in reduced growth that increases with transplant size. Research has demonstrated that smaller transplanted trees become established more quickly and ultimately result in larger trees in the landscape in a few years. Additional studies dispute these findings. This paper provides a review of current research on the effect of tree size on transplant establishment.

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This study evaluated the impact of paclobutrazol (PBZ) on the overall growth and vitality of root-pruned, field-grown live oak (Quercus virginiana). Live oak trees with 10-cm trunk diameter (measured 30 cm aboveground) were treated with full rate (0.8 g·cm−1 trunk diameter) of PBZ as basal drenches, full or half rate (0.8 or 0.4 g·cm−1 trunk diameter) of PBZ and trenching at 45 cm from trunk, full or half rate of PBZ and trenching at 60 cm from trunk, trenching alone at 45 or 60 cm from trunk, and only water. Trunk diameter and canopy growth was significantly reduced (P < 0.001) and new root growth was also reduced by applications of PBZ, root pruning, or both. Starch content in twigs decreased and glucose content increased on treatment by full-label rates of PBZ and root pruning at 60 cm. PBZ and/or root pruning caused slight improvements in chlorophyll fluorescence (Fv/Fm). Results of this research indicate that PBZ (full rate) in combination with root pruning (45 cm) reduces tree growth and exhibits an overregulation effect for at least 16 months after treatment. Therefore, PBZ applications on root-pruned trees can temporarily decrease root and tree growth and improve foliage chlorophyll fluorescence.

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Effects of washing and storing soil core samples of apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. (syn. M. domestica Borkh. non Poir.)] roots were studied to determine root losses from processing samples. Root losses were assessed by measuring root lengths before and after elutriation and storage at 4 °C (39.2 °F). The accuracy of the automated root length scanner to measure individual fine roots [<1 mm (0.04 inch) diameter] of varying lengths was evaluated by first measuring roots, then cutting the roots into 2 to 3 cm (0.79 to 1.18 inch) lengths and rescanning. There was a significant relationship between the measurement of cut and noncut roots (r 2 = 0.93). Losses from elutriating samples with cut and noncut roots indicated a mean loss of50% for samples with cut roots and 34% for samples with noncut roots (P ≤ 0.01). Total mean root loss (elutriation loss of noncut roots and degradation loss in cold storage) for the 12-month period ranged from 34% at month 0% to 53% at month 12 (P ≤ 0.01). Mean root degradation losses from long-term cold storage ranged from 6% at month 1 to 19% at month 12 (P ≤ 0.01). No losses were identified for roots with diameters of 1 to 5 mm (0.04 to 0.20 inch) and 5 to 10 mm (0.20 to 0.39 inch). A data correction curve was developed to correct root length data (<1 mm) for root losses associated with processing of soil cores.

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