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• PGRs changed plant growth dynamics. • Trinexapac-ethyl, paclobutrazol, flurprimidol, mefluidide and ethephon reduced plant growth. • Gibberellic acid resulted in higher plant growth. • PGRs resulted in reduced mechanical strength parameters. • Mechanical traits depends on rate of paclobutrazol, flurprimidol and gibberellic acid. Plant growth regulators (PGRs) are widely used on sport turfgrass to reduce mowing frequency and inhibit seedhead formation. However, PGRs may also affect turf colour, density and wear tolerance. The objective of this study was to examine the effects of plant growth regulators on the mechanical properties of leaves of perennial ryegrass (Lolium perenne L.). A pot trial was conducted in three seasons in 2016-2018. Three cultivars were tested, 'Barlicum', 'Vulcanus', and 'Info'. Six different PGRs, trinexapac-ethyl, paclobutrazol, flurprimidol, mefluidide, ethephon and gibberellic acid, were applied at five different rates. An untreated control turfgrass was also tested for each cultivar. The turfgrass height was measured using a falling plate metre. The biomechanical parameters, i.e., strain-at-break, stress-at-break, modulus of elasticity and work-to-break, were determined using a tensile testing machine. All tested PGRs significantly changed plant growth dynamics. Trinexapac-ethyl, paclobutrazol, flurprimidol, mefluidide and ethephon application reduced plant growth. Gibberellic acid resulted in higher plant growth. This effect was usually observed at 7, 14 and 21 days after PGR application. Perennial ryegrass leaves under tensile stress exhibited a characteristic behaviour with a nearly linear initial period followed by a decrease in the stress rate under a constant strain rate. All PGRs resulted in reduced mechanical strength parameters, namely, stress-at-break and modulus of elasticity. Gibberellic acid also resulted in lower strain-at-break. The work-to-break parameter was affected by all PGRs except ethephon. The PGRs application rate significantly affected certain mechanical parameters only when paclobutrazol, flurprimidol and gibberellic acid were used. [ABSTRACT FROM AUTHOR]

• Effect of PGRs was in the wavelength range from 540 to 650 nm. • Gibberellic Acid resulted in lighter leaves with higher yellow hue. • Paclobutrazol and Trinexapac Ethyl had a beneficial influence on colour and turf quality. • Flurprimidol and Mefluidide did not change turfgrass colour and quality. Plant growth regulators (PGRs) are used on turfgrass to slow vertical growth and reduce mowing intensity. However, turfgrasses sometimes exhibit some leaf discolouration after PGR applications. The objective of this study was to determine the effect of different rates of PGRs on turfgrass quality with a special focus on colour characteristics. Three cultivars of perennial ryegrass (Lolium perenne L.) were used in an experiment. Six PGRs were used, namely, Trinexapac Ethyl, Paclobutrazol, Flurprimidol, Mefluidide, Ethephon and Gibberellic Acid, at five different rates. A control without the addition of PGRs was also tested simultaneously. The measurement of leaf colour was performed using a portable spectrophotometer and is presented in CIE Lab colour space. The turfgrass quality was assessed by a visual score. The results showed that the turfgrass quality was significantly different regarding the perennial ryegrass cultivar, treated with different PGRs rates. The changes owing to different PGRs rates appeared in the wavelengths ranging from 540 to 650 nm. PGRs application significantly affected L , b and a colour components. Gibberellic Acid application resulted lighter leaves with higher yellow hue and in a lower score of overall appearance and turf colour assessment. Paclobutrazol and Trinexapac Ethyl, had a beneficial influence on colour characteristics and turf quality. Flurprimidol and Melfuidide had no effect on turfgrass colour and quality after PGR treatment. The changes in colour of turf of perennial ryegrass correlated with PGR rates. Higher rates resulted in increased intensity of discolouration. The results of the spectrophotometric analysis of leaf colour corresponded with visual turf colour assessment. However, visually scored turfgrass did not show differences between PGR rates. [ABSTRACT FROM AUTHOR]