Primo Effects on Turfgrass Water Use
Water is important in the survival of turfgrass plants. In general, plants are comprised of 75 to 90 percent water, but only one to three percent is used for metabolic processes. The remainder is used in the transpirational process. When water becomes limited, turf growth is greatly affected. In semi-arid, arid, and desert regions turfgrasses can experience periodic or seasonal water deficits. Even turfgrasses in regions where seasonal wet periods exist, periods of moisture stress can occur.
Figure 1. When turfgrasses suffer temporary moisture loss it is called wilt. One of the signs of wilting is footprinting.
A major mechanism that plants handle moisture deficits is through avoidance. Avoidance is the ability of a turfgrass plant to postpone plant water loss by reducing transpiration and/or increasing water uptake. Turfgrass plants can reduce transpiration through early stomatal closure, leaf rolling, presence of hairs on the leaf blade that reduce evaporation from the leaf surface, and a thicker cuticle layer.
Plant growth regulators (PGR) have the potential to lower water use by slowing the growth of the turfgrass plant. PGRs suppress shoot growth by limiting cell elongation. The primary mechanism for cell elongation is through active transport of solute, which results in water uptake causing expansion of the cell walls. PGRs, through the suppression of cell elongation, produce a short compact turf with a reduced evapotranspiration (ET) rate. PGRs are reported to reduce ET between 18 to 29 % for warm and cool season turfgrasses1,2.
Variation does exist among the PGRs with regard to reducing ET. In general, multiple applications of mefluidide and ethephon for the purpose of reducing ET would not be recommended. Mefluidide has been reported to cause chlorosis3 and a reduction in root length density2,3. Ethephon reduces root growth and root length density2,3. Paclobutrazol and flurprimidol are variable in their effects1,2,3.
Trinexapac-ethyl (TE), which goes by the trade name Primo Maxx is the most effective of the PGRs for reducing transpiration rates with no detrimental effect on root growth. TE has been reported to enhance turf quality during drought periods, while ethephon and mefluidide had a negative effect and flurprimidol had no effect3.
Internally, TE enhances the drought tolerance of turfgrasses. Research has demonstrated that the antioxidant concentration of a plant is closely associated with its drought tolerance4. TE has been associated with increased activity of the endogenous antioxidant, superoxide dismutase (SOD). SOD reportedly plays a role in drought tolerance.
Several of you may have tried using PGRs for reducing the turf's water use rate. Of the PGRs available, TE on either cool or warm season turfgrass will work most effectively in a water management program. Frequent use of TE should help reduce ET and improve the drought tolerance of the turf. One note of caution, proper timing of multiple applications is critical. Research has shown that when the PGR wears off, a growth flush and increase in ET will occur for a short period of time6.
Figure 2. Prolonged periods without moisture is termed drought. In this case this is a bermudagrass turf.
- Green, R.L., Ki S. Kim, and J.B. Beard. 1990. Effects of flurprimidol, mefluidide, and soil moisture on St. Augustinegrass evapotranspiration rate. HortScience 25:439-44
- Marcum, K.B. and H. Jiang. 1997. Effects of Plant Growth Regulators on tall fescue rooting and water use. J. Turfgrass Mgt. 2:13-27.
- Jiang, H. and J. Fry. 1998. Drought responses of perennial ryegrass treated with plant growth regulators. HortScience 33:270-27
- Smirnoff, N. 1993. The role of active oxygen in the response of plants to water deficit and desiccation. New Phytol. 125:27-58.
- Zhang, X. and R.E. Schmidt. 2000. Application of Trinexapac-ethyl and propiconazole enhances superoxide dismutase and photochemical activity in creeping bentgrass. J. Amer. Soc. Hort. Sci 125:47-51.
- Doye, J.M. and R.C. Shearman. 1985. Plant growth regulator effects on evapotranspiration of a Kentucky bluegrass turf. Agronomy Abstracts.
About the author
Dr. Karl Danneberger is a professor of Turfgrass Science at The Ohio State University. Dr. Danneberger's contact information can be found here. You may also follow Dr. Danneberger on Twitter: