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Songul Severmutlu, Nedim Mutlu, Ercan Gurbuz, Osman Gulsen, Murat Hocagil, Osman Karaguzel, Tiffany Heng-Moss, Robert C. Shearman, and Rock E. Gaussoin

opportunity for water conservation when warm-season turfgrass species were used under Mediterranean-like climate in Australia, but data on drought resistance and water conservation are lacking for the Mediterranean region. Bermudagrass, buffalograss

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James E. Hook and Wayne W. Hanna

In our study, we sought to determine if an experimental cultivar of centipedegrass [`TC178'; Eremochloa ophiuroides (Munro) Hack.] had superior turf characteristics under extended droughts. Common centipedegrass (CC), vegetatively propagated `TC178' (VG178), and seed-propagated (F3) `TC178' (SD178) were evaluated in a 2-year controlled watering study that compared turf characteristics and drought resistance. The grasses were established under an automated rainfall shelter and were subjected to three drought regimes: watered twice per week (no stress), 2 to 3 weeks between watering (moderate), and 4 to 6 weeks between watering (severe). Turf characteristics (visual rating and clipping biomass) were measured weekly and soil water content profiles were measured daily. Visual ratings among cultivars were similar for no-stress conditions, but visual ratings of SD178 and VG178 were 18% higher than for CC for moderate stress and 28% higher for severe stress. At the end of moderate stress periods, clipping biomass of VG178 was 24% greater than for CC, but by the end of the severe stress periods, biomass from VG178 was 22% lower than for CC. Available soil water content profiles indicated that the three cultivars extracted soil water at the same rate. Visual ratings and growth decline with survival under severe stress showed that VG178 and SD178 had significantly better drought resistance than CC. `TC178' provides a superior appearance turf that will stand up to the droughts common in its adapted region.

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Mohamed A. Shahba, Mohamed S. Abbas, and Saad F. Alshammary

The demand for water has increased more than 300% during the past five decades ( Huffman, 2004 ). Therefore, the development of efficient irrigation management programs as well as the improvement of drought resistance of turfgrasses has become

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P. H. Dernoeden and J. D. Butler

Abstract

In a field test of 25 Kentucky bluegrass cultivars (Poa pratensis L.) “common types” were generally more drought tolerant than recently introduced turf types. ‘Code 95’, a common type, and ‘Merion’ exhibited high drought resistance and produced turf of good color, texture, and density. Turf mowed at 3.8 cm was more resistant to drought than turf maintained at 1.9 cm.

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Fan Cao, Yunchu Wei, Xinwang Wang, Yongrong Li, and Fangren Peng

/dV), where V is the volume of free water, and P is pressure potential. The most bulk elastic modulus (ε max ), which represented the physical property of the cell wall, was also chosen and measured as one parameter for the evaluation of drought resistance

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W. Alan Erb, Arlen D. Draper, and Harry J. Swartz

Abstract

Open-pollinated species, interspecific hybrid seedling populations, and selected clones propagated by softwood cuttings and tissue culture were used to further evaluate the use of dry soil to screen blueberry seedlings for drought resistance. These different propagation types of Vaccinium (subgenus Cyanococcus) were screened for drought resistance in a Galestown fine sandy loam soil. The soil was permitted to dry to progressively higher soil tension levels to a maximum of 0.8 MPa. The plants were evaluated by scoring them on a 1 to 9 shoot damage rating scale and by determining the fraction of total biomass partitioned as roots. Drought resistance in blueberries is heritable and there is a high degree of genetic diversity within and among Vaccinium spp. for resistance to water deficits. Southern species (Vaccinium darrowi Camp, V. elliottii Chapman, and V. ashei Reade) were more drought-resistant than northern species (V. corymbosum L., V. vacillans Torrey, and V. myrtilloides Michaux), which demonstrated the reliability of this soil screening method. Clones with half their germplasm from southern species were usually drought-resistant. This screening method can be used to select for shoot and root vigor and drought resistance in 6- to 7-month-old blueberry seedlings.

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J.D. Fry and W.S. Upham

The relative drought resistance of turf-type tall fescue (Festuca arundinacea Schreb.) cultivars compared to forage-type cultivars has not been well-documented. Greenhouse and field studies were conducted between 1991 and 1994 to determine rooting potential and drought response of a slow-growing, turf-type tall fescue (`MlC18'), a turf-type cultivar with a moderate growth rate (`Mustang'), and a forage-type cultivar (`Kentucky-31'). In the greenhouse, rooting was determined in sand or calcined clay using clear, polyethylene root tubes 4 cm in diameter by 122 cm deep. Root length density (RLD) was measured for 0- to 30-, 30- to 60-, 60- to 90-, and 90- to 120-cm depths. No differences were observed in RLD at the 0- to 30-cm depth. At other depths, RLD of `Mustang” was generally superior to that of `K-31' and `MlC18'. During a 3-week dry-down in the field in 1994, `MlC18' exhibited greater drought stress and a higher canopy minus air temperature than other cultivars. Advantages afforded by reduced mowing of slow-growing tall fescue cultivars may be negated by reduced drought resistance.

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W. A. Erb, A. D. Draper, and H. J. Swartz

Abstract

Two methods of evaluating seedling drought resistance in Vaccinium (blueberry) spp. were examined. Twenty interspecific populations were greenhouse-grown and either matric-stressed in a dry 1 sand : 1 soil medium or osmotic-stressed in a nutrient solution containing polyethylene glycol (PEG). In both tests, population means were separated statistically by shoot damage ratings. The correlation (r = 0.46) between the two tests was positive and significant. Progenies of clones JU64 and JU62, which are sister seedlings (V. myrsinites Lamark × V. angustifolum Aiton), were the most drought-resistant. The soil screening test appeared more accurate because it grouped populations with common parentage. These tests indicated that the progenies differ in genetic capacity to resist drought.

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Douglas S. Chapman and Robert M. Augé

Understanding physiological drought resistance mechanisms in ornamentals may help growers and landscapers minimize plant water stress after wholesale production. We characterized the drought resistance of four potted, native, ornamental perennials: purple coneflower [Echinacea purpurea (L.) Moench], orange coneflower [Rudbeckia fulgida var. Sullivantii (Beadle & Boynt.) Cronq.], beebalm (Monarda didyma L.), and swamp sunflower (Helianthus angustifolius L.). We measured a) stomatal conductance of leaves of drying plants, b) lethal water potential and relative water content, and c) leaf osmotic adjustment during the lethal drying period. Maintenance of stomatal opening as leaves dry, low lethal water status values, and ability to osmotically adjust indicate relative drought tolerance, with the reverse indicating drought avoidance. Echinacea purpurea had low leaf water potential (ψL) and relative water content (RWC) at stomatal closure and low lethal ψL and RWC, results indicating high dehydration tolerance, relative to the other three species. Rudbeckia fulgida var. Sullivantii had a similar low ψL at stomatal closure and low lethal ψL and displayed relatively large osmotic adjustment. Monarda didyma had the highest ψL and RWC at stomatal closure and an intermediate lethal ψL, yet displayed a relatively large osmotic adjustment. Helianthus angustifolius became desiccated more rapidly than the other species, despite having a high ψL at stomatal closure; it had a high lethal ψL and displayed very little osmotic adjustment, results indicating relatively low dehydration tolerance. Despite differences in stomatal sensitivity, dehydration tolerance, and osmotic adjustment, all four perennials fall predominantly in the drought-avoidance category, relative to the dehydration tolerance previously reported for a wide range of plant species.

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P. H. Demoeden and J. D. Butler

Abstract

There was no correlation between drought resistance and several plant characteristics of 12 Kentucky bluegrass cultivars (Poa pratensis L.) rated high, intermediate, or low in drought resistance on the basis of Visual response to drought stress.