Modified Gibberellins Retard Growth of Cool‐Season Turfgrasses†

Abstract

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.

Trinexapac‐Ethyl and Iron Effects on Supina and Kentucky Bluegrasses Under Low Irradiance

“…Foreman and Marshall (1990) showed N‐t‐butylcarbonyl‐N‐(4′‐chlorophenyl methyl) aminopyrazine, another GA inhibitor, reduced leaf length of perennial ryegrass ( Lolium perenne L.) without altering mesophyll cell number. Since there is no suggested or reported evidence that TE reduces cell wall deposition, suppression of cell enlargement by TE (King et al, 1997) may have increased the relative total cell wall content. This phenomenon could enhance wear tolerance and account for the increased rigidity of TE‐treated turf compared with untreated turf (unpublished data, 1993–1996).…”

Relationship between gibberellins, height, and stress tolerance in barley (Hordeum vulgare L.) seedlings

“…showed that these compounds are as effective as trinexapac-ethyl in reducing growth in cooLseason turfgrasses (King et al, 1997).…”

16,17-Dihydro Gibberellin A5 Competitively Inhibits a Recombinant Arabidopsis GA 3β-Hydroxylase Encoded by the GA4 Gene

“…16, (Fig. 1) and other ring D-modified GA 5 derivatives (Mander et al, 1995(Mander et al, , 1998a(Mander et al, , 1998b are structurally very similar to GA 20 .When these ring D-modified GAs are applied to many higher plant species, and especially to grasses, they can effectively inhibit shoot growth (Evans et al, 1994a(Evans et al, , 1994bTakagi et al, 1994;Foster et al, 1997;King et al, 1997King et al, , 2004. Associated with the reduction in shoot elongation is a concomitant reduction in levels of endogenous 3b-hydroxylated GAs and an increase in one or more of the 3-deoxy precursors (Foster et al, 1997;Junttila et al, 1997;Zhou, 2000).…”