TURF TIPS
By Jim Brosnan, Ph.D., Assistant Professor; Greg Breeden, Extension Assistant; Tom Samples, Ph.D., Professor; and John Sorochan, Ph.D. Associate Professor, The University of Tennessee; and T.J. Serentis, Ph.D., Penn State University
lant growth regulators (PGRs) cause changes in turfgrass growth and development. The use of PGRs in turfgrass management has become increasingly popular in recent years. In addition to reducing mowing frequency, PGR applications also enhance growth characteristics and improve the ability of a turfgrass to cope with stress.
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How do PGRs work? Turfgrass plants contain six hormones that affect growth and development. While each hormone plays a critical role in these processes, the majority of PGRs used on turfgrass target the biosynthesis of gibberellins. 20
TENNESSEE TURFGRASS
Two types of PGRs affect the expression of gibberellins in turfgrass plants. Class A PGRs are foliar-absorbed materials that inhibit the production of gibberellins near the end of the gibberellin biosynthesis pathway. Trinexapac-ethyl (trade name, Primo Maxx) is an example of a Class A PGR used regularly in turfgrass management. Class B PGRs are root-absorbed materials that stop the production of gibberellins near the beginning of the gibberellin biosynthesis pathway. Paclobutrazol (trade name, Trimmit) and flurprimidol (trade name, Cutless) are examples of Class B PGRs used regularly in turfgrass management. Depending on the use rate, these materials suppress vertical shoot growth by approximately 50% for either 4 weeks (Class A) or 6 to 8 weeks (Class B).
AUGUST/SEPTEMBER 2009 Email TTA at: tnturfgrassassn@aol.com