Bermudagrass is the most used warm season turfgrass for sports and ornamental purposes wherever climatic conditions sustain its growth (Richardson, 2002). The stoloniferous-rhizomatous growth habit and the aggressiveness of bermudagrass are key features enabling quick establishment by vegetative propagation and allow turf to promptly recover from wear and divots (Beard, 1973). While it is appreciated for establishment and recovery, a vigorous growth is considered a drawback for routine maintenance since frequent mowing and verticutting are required to maintain high quality standards (Waltz and Whitwell, 2005).
Chemical growth suppression artificially reduces vertical plant growth to reduce mowing frequency. Since its release in 1991 for turfgrass use, TE has become an increasingly popular plant growth regulator (Ervin and Zhang, 2008).
TE is foliar absorbed and its intended action is to reduce cell elongation by inhibiting gibberellic acid biosynthesis, at a late stage. In particular, gibberellic acid biosynthesis is stopped between GA1 and its inactive precursor (GA20). The reduced concentration of GA1 reduces shoot elongation thus producing the desired effect of growth suppression (Ervin and Zhang, 2008).
Besides the reduction of vertical growth, the effects of TE application on bermudagrass stolon growth have been documented. In a field trial carried out by Fagerness and Yelverton (1998), they described a decreased stolon length in TE-treated bermudagrass stands, with stolon number being unaffected. In two experiments carried out in a controlled environment, Fagerness and Yelverton (1999) reported little impact on stolon number and length with no effect on stolon biomass while Fagerness et al. (2002) observed a higher number of stolons on TE-treated plants.
In a 2-year study, inconsistent effects through the years on morphological parameters such as stolon density and stolon internode length were also reported by Richardson (2002). McCarty et al. (2011) reported a minimal impact of TE on lateral regrowth of ‘TifEagle’ hybrid bermudagrass.
Several other effects have been documented following the application of TE on bermudagrass. A quality enhancement of ultradwarf bermudagrasses was recorded on salt-stressed turf (Baldwin et al., 2006) and in reduced light conditions (Baldwin et al., 2009; Bunnel et al., 2005). Williams et al. (2010) reported an increased tolerance to simulated traffic and enhanced quality of six bermudagrass cultivars as a result of TE application. Better fall color retention and faster spring green-up were reported on hybrid bermudagrass treated during the growing season (Richardson, 2002). Enhanced shoot density was described by Fagerness et al. (2001), while inconsistent results were found for freezing tolerance of TE-treated bermudagrass (Fagerness et al., 2002; Richardson, 2002).
Based on the description of several secondary effects, it has become evident that different metabolic pathways are affected in the plant following TE application. Reduced cell elongation results in a higher chloroplast density and a higher photosynthetic net assimilation at canopy level. Enhanced production of total nonstructural carbohydrates (TNC) is coupled with a lower TNC demand because of reduced cell elongation, thus generating an excess of TNC redirected to the basal portion of plants where root activity is stimulated. Enhanced root activity promotes cytokinin production which in turn stimulates the formation of new stems from crowns. Therefore, inhibition of GA1 seems to be the start of a chain of metabolic events that ultimately lead to the modification of some physiological functions (Ervin and Zhang, 2007, 2008).
Node tissue formation occurring under the effect of TE and altered physiological functions could be associated with modifications in subsequent plant stages such as node sprouting and daughter plant development. Based on this assumption, the purpose of this study was to investigate: 1) TE effects on plants stolon production, stolon growth rate, and node production after a single application and during the period of TE effectiveness, 2) the effect of TE, secondary products, or both on node vitality and daughter plant characteristics, and 3) to assess whether the aforementioned effects on nodes were permanent or transient and if a gradient could be detected throughout the stolon length.
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Baldwin, C.M., Liu, H., McCarty, L.B., Luo, H. & Toler, J.E. 2009 Nitrogen and plant growth regulator influence on ‘Champion’ bermudagrass putting green under reduced sunlight Agron. J. 101 75 81
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