188 Moore and McGarry: Potential for Bark Patch Graſting to Facilitate Tree Wound Closure and temperature have been shown to influence wound responses (Hudler and Banik 1986). Callus production and wound closure can be expected to be greatest in spring and early- summer (Clearwater et al. 2007). The large number of active young leaves gives rise to high levels of IAA, which moves basipetally; active root growth produces high levels of cytokinins, which move acropetally; while high levels of both stimulate callus production, especially if water and photosynthate are available (Aloni 2015). Good growth by plants at this time of the year increases the production of sugars, which act as signals that further stimulate IAA produc- tion, especially if there is rapid transpiration and available water (Lilley et al. 2012) The warmer temperatures also stimulate increased auxin and cytokinin production in young leaves and roots tips, respectively, which continues until very warm temperatures and/or reduced water supply change phytohormone production in response to stress (Aloni 2015). Such changes are significant in the subsequent differentiation of the callus. The Effect of Species on Tree Responses to Damage There is genetic control of wound closure (Shigo 1986; Kozlowski et al. 1991) and compartmen- talization (Shigo and Marx 1977; Shortle 1979; David-Schwartz and Sinha 2007). There are large differences between tree species when it comes to the rate of wound responses aſter pruning (Mer- cer 1979). Significant variability in wound clo- sure rates exists within tree populations (Neely 1988b), and the time it takes for the callus to com- plete wound closure varies with species (Neely 1988a). Not only does cambial activity differ from species to species, but the rate of formation of boundaries within a tree aſter wounding var- ies with species as well (Shigo 1986; Kramer and Kozlowski 1979; Kozlowski et al. 1991; Waisel 1991). Variation also exists within trees of the same spe- cies, as identical wounds inflicted on trees of the same species, at the same time, have different rates of wound closure (Neely 1988b). It has been shown that some clones, or varieties of trees are particularly good at compartmentalizing, while other trees of the same species are poor (Mercer 1979; Shigo 1986; Santamour 1987a). Differences between and within ©2017 International Society of Arboriculture plant species are to be expected as trees may be ring or diffuse porous and have vessels and tracheids of different diameter sizes, both of which can influ- ence the free flow of phytohormones and so also their concentration in plant tissues (Aloni 2015). Furthermore, the growth rate of the individual tree can influence the production of and response to hormones. Graſting, which has been practiced for centuries, may have unwittingly assisted in the selection of strong compartmentalization as a characteristic of common horticultural species, as trees that graſt successfully tend to be strong at wound compartmentalization (Shigo 1991). Grafting The process of graſting is based on the ability of the cambium, or other tissue, to form the callus at the junction of the joining tissues and relies on the callus differentiating to connect the xylem and phloem (McGarry 2001; Moore 2013). Successful graſts are usually between plants of the same genus; however, in some instances, plants of different genera, but of the same family, may be compat- ible (Moore 2013). The type of graſting that is particularly useful in relation to tree wounds is the bridge graſt, which is used to restore sap flow in repairing the bark of a damaged tree trunk (Smith 2008). Bridge graſting, sometimes referred to as repair graſting (Smith 2008), is also used to repair bark damage to trees from grazing animals, such as deer, horses, and rabbits (Anonymous 2004). A number of scions are prepared and in- serted under the intact bark across the wound. Most plants that can be graſted will respond suc- cessfully (Moore 2013), especially in early spring just as active growth of the tree is beginning and the bark is slipping easily (Hartmann et al. 2010). Patch budding/graſting is a method of graſting that involves removing a square patch, contain- ing one bud, from the scion and inserting it into a same-sized square wound that has been prepared in the rootstock. The relationship between scion and stock at the cellular level is becoming better under- stood (Koepke and Dhingra 2013), but the basip- etal movement of IAA is a significant factor in the production and subsequent differentiation of cal- lus and the vascular connection between scion and stock tissues (Grebe 2004; Aloni et al. 2010; Aloni 2015). Some of the seasonal influences observed on
September 2017
| Title Name |
Pages |
Delete |
Url |
| Empty |
Ai generated response may be inaccurate.
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success.
Downloading PDF
Generating your PDF, please wait...
This process might take longer please wait
