Establishing turfgrass in shaded environments can create a unique maintenance challenge. Approximately 20% to 25% of all turfgrasses are grown in low light intensity environments (Beard, 1973). Reductions in light intensity may decrease the photosynthetic capacity of turfgrasses and lead to the depletion of carbohydrate reserves (Schmidt and Blaser, 1967; Winstead and Ward, 1974). Changes in physiological characteristics may alter zoysiagrass (Zoysia spp.) morphology and result in reductions in turfgrass aesthetic quality. Turfgrasses grown in shade may exhibit reduced leaf and stem width, increased leaf length and plant height, reduced shoot density, longer internodes, reduced tillering, and a more upright growth habit (Beard, 1973; Dudeck and Peacock, 1992; McBee and Holt, 1966; Peacock and Dudeck, 1981; Wherley et al., 2005; Wilkinson and Beard, 1974; Winstead and Ward, 1974). Previous research has reported reductions in turfgrass quality and growth rate of several turfgrass species grown under reduced light intensity environments (Barrios et al., 1986; Beard, 1965; Jiang et al., 2004; McBee and Holt, 1966; Peacock and Dudeck, 1981; Tegg and Lane, 2004).
Zoysiagrass has demonstrated good tolerance to reduced light intensities (Morton et al., 1991; Qian and Engelke, 1999a; Qian et al., 1998). It is a warm-season, perennial turfgrass native to parts of China, Japan, and Korea (Engelke and Anderson, 2003). Zoysiagrass is adapted throughout the southern humid region of the United States to the northern transition zone. It forms a dense, uniform turf through the production and spread of rhizomes and stolons (Turgeon, 2008). Zoysiagrass is predominantly used on golf courses, athletic fields, residential lawns, and commercial landscapes. Adaptation to a wide range of environmental conditions has further led to an increase in zoysiagrass popularity. Zoysiagrass tolerates moderate salinity levels (Marcum et al., 1998; Qian et al., 2000), moderate drought conditions (Qian and Engelke, 1999b; White et al., 2001), and exposure to low temperatures (Dunn et al., 1999; Patton and Reicher, 2007; Warmund et al., 1998). Extensive documentation exists on the tolerance of ‘Diamond’ zoysiagrass to shaded environments (Engelke et al., 2002; Qian and Engelke, 1999a, 1999c; Qian et al., 1998). Acceptable turfgrass quality (6 or greater) was maintained by ‘Diamond’ zoysiagrass when subjected to 81% or less shade for 6 weeks (Qian and Engelke, 1999a). However, a wide range of relative shade tolerance exists between turfgrass species (Barrios et al., 1986; McBee and Holt, 1966; Morton et al., 1991; Qian and Engelke, 1999a, 1999c; Qian et al., 1998; Tegg and Lane, 2004; Winstead and Ward, 1974).
Evaluating the response of multiple zoysiagrass genotypes grown in shade may provide additional information on the ability of these grasses to tolerate reduced light environments. Further identification of shade-tolerant genotypes may provide turfgrass managers with additional options for shaded environments. Therefore, the objective of this research was to evaluate the relative difference in growth response to three light intensities among six zoysiagrass genotypes under artificial shade conditions.
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