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| Web URL(s): | http://archive.lib.msu.edu/tic/rpr/1985/7717, Texas A&M, Beard.PDF
Last checked: 03/29/2013
Requires: PDF Reader |
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| Publication Type:
| Report |
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| Material Type: | Manuscript |
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| Monographic Author(s): | Beard, James B. |
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| Author Affiliation: | Turfgrass Physiologist, Texas A&M University |
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| Monograph Title: | Second Year Progress Report Concerning Physiological Investigations in Developing Water Conserving, Minimal Maintenance Turfgrasses and Cultural Systems: Volume II, 1985. |
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| Publishing Information: | [College Station, Texas]: Texas A&M University |
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| # of Pages: | 95 |
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| Collation: | 43, [52] pp. |
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| Abstract/Contents: | "The original proposed time schedule for the major research objectives in developing water conserving, minimal maintenance turfgrasses and cultural systems is found on page 6. The current progress is reasonably close to the original schedule. Whether this will be sustained in the upcoming year as we start to address the drought resistance dimension in more detail is difficult to foresee. In terms of the scientific subobjectives and their status, these are shown on page 7. Scientific papers that have been published are included in the Appendix. From research conducted over the first two years, the following conclusions have been drawn. A. Minimal Water Use Rates: 1. The major warm season turfgrass species vary substantially in water use rates.; 2. The comparative interspecies water use rates are of a magnitude to have practical significance for field applications.; 3. Initial data suggest that there may be as much variation among cultivars within a warm season species as there is at the interspecies level.; 4. The primary plant parameters affecting the evapotranspiration rate are a high canopy resistance and a low leaf blade area.; 5. These plant morphological parameters are valid in interpreting the differentials in water use rates among elven major warm season perennial turfgrasses.; 6. Fortunately, these morphological parameters can be easily and rapidly assessed for use in screening thousands of clonal plantings for low water use rates in a breeding program.; 7. These morphological factors are subject to modification by a number of cultural practices; thus, the turf manager can significantly affect the water use rate of a given turfgrass species.; 8. Both the warm and cool season turfgrass species possess significant differences in stomatal density.; 9. Both warm and cool season turfgrasses vary significantly in stomatal distribution over the leaf. In the case of warm season turfgrasses, there is a distinct relationship between the stomatal arrangement and their associated subfamily classifications of Eragrostoideae and Panicoideae.; 10. A significantly higher stomatal density was found on the adaxial side of the leaf in comparison to the density found on the abaxial side, with the exception of Kentucky 31 tall fescue.; 11. There was no relationship between an increase in the evapotranspiration rate and a higher stomatal density. In fact, there was a trend to an inverse relationship.; 12. Although the stomatal characterization studies have not elucidated a component contributing to a reduced evapotranspiration rate, these results may be useful in the upcoming mechanistic studies on drought resistance.; 13. It was found that the results of the potential evapotranspiration rate assessments across a range of warm season species can be reproduced in a water-heat stress simulation chamber that are representative of evapotranspiration rates monitored in the field, providing the canopy structure and leaf extension rates are comparable, as controlled by the cultural practices employed.; 14. The water-heat stress simulation module can be used for the measurement of comparative evapotranspiration rates of turfgrasses.; 15. The major cool season turfgrass species vary substantially in water use rates.; 16. The comparative water use rate differentials of turfgrasses are of a magnitude that is practical for usage in field applications.; 17. Initial data suggest that there may be as much variation among cultivars within a cool season species as there is at the interspecies level.; 18. Growth inhibitors do possess a valid potential for use in reducing evapotranspiration rates of turfgrasses, with an effective period of up to 14 weeks and a significant order of reduction ranging from 17 to 28%.; 19. The evapotranspiration rate increases as the cutting height is raised.; 20. The evapotranspiration rate increases as the nitrogen nutritional level is increased.; 21. The relative significance of an increased cutting height or nitrogen nutritional level on the evapotranspiration rate varies with the particular turfgrass species. In high nitrogen requiring turfgrasses, the evapotranspiration is most affected by changes in the nitrogen level, whereas in low nitrogen requiring turfgrasses, evapotranspiration is affected by changes in mowing height.; 22. There is genetic diversity within the bermudagrass species that contributes to a variance in potential evapotranspiration (ET). This diversity can be measured and statistically analyzed.; 23. Associated plant morphological characteristics of bermudagrasses can be correlated with potential evapotranspiration. Among the characteristics documented are leaf and shoot density, canopy orientation, leaf extension rate, and leaf width.; 24. In general, bermudagrass cultivars with a low potential evapotranspiration under non-limiting water conditions had high shoot and leaf densities, horizontal or near horizontal canopy orientations, narrow leaves, and a low to moderate leaf extension rate. The converse was also demonstrated.; 25. Visual assessment via the canopy resistance-leaf extension concept, with possible refinements through observer training, offers a rapid, economical approach for screening large numbers of bermudagrass clonal plantings under field conditions for low water use rates.; B. Enhanced Rooting/Water Absorption: 1. Initial experiments suggest that the root hair dimension of turfgrass root characterization has been overlooked and that over the past three decades, far too much emphasis has been placed on total root mass and depth.; 2. The rooting depths and total root weights of the major warm season turfgrasses vary substantially in terms of interspecies rooting potentials.; 3. The greater rooting capability of the bermudagrasses shown in this study is no doubt a significant factor in the overall drought resistance mechanism.; 4. Preliminary data suggest that, based on the high correlation between both root weight and length with the shoot weight, there is a potential for the use of shoot biomass as a plant marker in selecting deep rooting plants, thereby avoiding time consuming root measurements. Much more research remains to be done to confirm this at the intraspecies level.; 5. Spring root decline (SRD) is a separate phenomenon rather than a result of other external stresses.; 6. There are two distinctly different dormancy phases for the root and shoot system of warm season perennial grasses, with root growth sustained after short dormancy occurs.;. 7. The spring root decline response has occurred in all ten warm season grasses investigated, which indicates that it is common to most warm season perennial grasses used for turfgrass purposes.; 8. Under controlled environment growth chamber conditions, the temperature threshold above which spring root decline is induced has been documented as 28°C (82°F). Temperatures above this threshold stimulate rapid shoot growth with probable redirection of carbohydrate reserves from the roots to the shoots, resulting in spring root decline. Temperatures below this level result in new root growth from the tips of existing roots with no evidence of spring root decline.; 9. Significant differences in rooting depth and root mass were found among the major cool season turfgrass species when grown under near optimum conditions.; 10. Certain cool season species, such as crested wheatgrass and the tall fescues, exhibited a stronger capability to sustain root growth under severe heat stress conditions.; 11. There are variations in rooting among the major cool season species, but the differentials are not nearly as great as observed under near optimum growing conditions.; C. Improved Drought Resistance: 1. The major warm season turfgrass species vary greatly in drought avoidance and in drought resistance, with comparative rankings being much different than had been previously assumed.; 2. Variations in drought avoidance and recovery is at great within most of the turfgrass species as the variation at the interspecies level.; D. Physiological Basis of Minimal Maintenance Turfgrasses: 1. Genetic diversity in terms of minimal maintenance turfgrasses can be observed as morphological, anatomical, and physiological plant parameters and can be statistically evaluated." |
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| Language: | English |
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| References: | Chapter refs |
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| See Also: | See also related item, "Determination of the resistance to sensible heat flux density from turfgrass for estimation of its evapotranspiration rate" Agricultural Meteorology, 25(1) 1981, p. 15-25, R=1851. R=1851
See also related item, "Key events in the seasonal root growth of bermudagrass and St. Augustinegrass" HortScience, 17(5) October 1982, p. 829-831, R=5920. R=5920
See also related item, "Resistances to evapotranspiration from a St. Augustinegrass turf canopy" Agronomy Journal, 75(3) May/June 1983, p. 419-422, R=487. R=487
See also related item, "An environmental genetics model for turfgrass improvement: physiological aspects" Proceedings of the Fifth International Turfgrass Research Conference, July 1-5 1985, p. 107-118, R=9000. R=9000
See also related item, "An environmental genetics model for turfgrass improvement: Developmental aspects" Proceedings of the Fifth International Turfgrass Research Conference, July 1-5 1985, R=9002. R=9002
See also related item, "Spring root decline (SRD): Discovery, description and causes" Proceedings of the Fifth International Turfgrass Research Conference, July 1-5 1985, p. 777-788, R=9072. R=9072
See also related summary article, "Plant stress mechanisms", Annual Turfgrass Research Report [USGA/GCSAA], 1985, pp. 15-17, R=7717. R=7717 |
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| Note: | "Jointly Sponsored By: United States Golf Association and Texas Agricultural Experiment Station"
"October 30, 1985"
Includes appendix: "Published Scientific Papers"; p. 43
Appendices include full copies of 6 other abstracts or items
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MSU catalog number: b5288203 |
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