The effect of an experimental growth retardant (WL83801) on leaf growth and development in Lolium perenne L.

Abstract

SUMMARYThe experimental growth retardant WL83801, applied as a root drench, had a rapid and persistent effect in retarding the growth and development of leaves in L. perenne. Leaves of the main shoot were greatly reduced in length, were broader, and appeared faster than in control plants. The rate of extension of individual leaves was greatly reduced in retarded plants but still followed a diurnal pattern that closely corresponded with temperature. There was evidence that leaf extension was far less responsive to temperature in treated plants. At the cellular level WL83801 had no significant effect on leaf blade cell number, thus reductions in leaf length were associated with the retardation of cell elongation. Changes in leaf structure were also observed.These changes in the pattern of leaf growth and development are discussed in relation to the primary mode of action of the growth retardant in interfering with gibberellin biosynthesis.

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

“…The developmental response in supina bluegrass may have been partly due to a redistribution of carbohydrates (Hanson and Branham, 1987) which increased tillering (Foreman and Marshall, 1990). Trinexapac‐ethyl likely increased the number of leaves by reducing the leaf‐extension period and plastochron, thereby accelerating leaf production (Foreman and Marshall, 1990). Foreman and Marshall (1990) reported an experimental GA inhibitor caused an increase in leaf width, a result also observed with TE under reduced irradiance (Stier, unpublished data, 1996).…”

“…Trinexapac‐ethyl likely increased the number of leaves by reducing the leaf‐extension period and plastochron, thereby accelerating leaf production (Foreman and Marshall, 1990). Foreman and Marshall (1990) reported an experimental GA inhibitor caused an increase in leaf width, a result also observed with TE under reduced irradiance (Stier, unpublished data, 1996). The increased leaf area index (LAI) resulting from increased leaf width and number would increase carbohydrate production (Quian and Engelke, 1999) and growth.…”

“…Shearman and Beard (1975) showed total cell wall content was correlated to turfgrass wear tolerance. 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.…”

Evaluating the use of plant hormones and biostimulators in forage pastures to enhance shoot dry biomass production by perennial ryegrass (Lolium perenneL.)

“…These changes in leaf elongation were due to a decrease in cell elongation, with cell numbers being unaffected. Leaf elongation of the retardant‐treated plants was also less responsive to increases in temperature, relative to leaf elongation of untreated, control plants …”

“…Associated with the reduced stem growth in perennial ryegrass caused by Moddus application are an increased number of seeds per spikelet, and thus improved floret site utilisation . Another GA biosynthesis inhibitor, WL83801 [ N‐t ‐butylcarbonyl‐ N ‐(4′‐chlorophenyl methyl)aminopyrazine], whose shoot growth retarding effects can be rescued by exogenous GA 3 application, was also shown to be effective in regulating leaf growth and development in perennial ryegrass plants . Application (as a root drench for pot‐grown plants) of WL83801 to perennial ryegrass plants significantly reduced the lengths of main shoot leaves, though they were broader and appeared sooner than main shoot leaves on control (untreated) plants.…”