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This article in CS

  1. Vol. 37 No. 6, p. 1878-1883
    Received: Dec 10, 1996

    * Corresponding author(s): rod.king@pi.csiro.au
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Modified Gibberellins Retard Growth of Cool-Season Turfgrasses†

  1. R. W. King ,
  2. C. Blundell,
  3. L.T. Evans,
  4. L.N. Mander and
  5. J.T. Wood
  1. C SIRO Plant Industry, GPO Box 1600, Canberra ACT 2601, Australia
    R esearch School of Chemistry, Institute of Advanced Studies, Australian National University, Canberra ACT 2601, Australia
    C SIRO Mathematical and Information Sciences, GPO Box 664, Canberra ACT 2601, Australia



Several modified gibberellins which inhibit shoot elongation have been assessed as turfgrass growth retardants. Dichloro-methano 16,17-dihydro GA5 (DMDGA5) effectively inhibited growth of the cool season grasses, Festuca arundinacea Schreb., Poa pratensis L., and Lolium perenne L. Turf growth (weekly cutting dry weight) was reduced by up to 70% in three separate field trials over three seasons. This inhibition lasted up to 5 wk before recovery to control growth rates and, often, there was then a transient enhancement of growth. DMDGA5 inhibited turf growth to the same extent as did the commercial turfgrass retardant, Trinexapac-ethyl (commercially formulated as Primo, Novartis, Inc., Basel, Switzerland). Daily water use was also 25 to 30% less over at least 4 wk in studies with mini-swards growing in controlled environment conditions. With isolated plants of two cultivars of P. pratensis (cvs Holt and Bronco) grown in controlled conditions leaf elongation rates were more than three-fold greater in long than short daylengths. Both Trinexapac-ethyl and DMDGA5 blocked most of this growth increase as did a related derivative, 16,17-dihydro GA5. Since these compounds inhibit gibberellin biosynthesis it appears that the extra growth in long days arises from an increase in gibberellin content.

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