Light Intensity Affects Gibberellic Acid Content in Kentucky Bluegrass

Abstract

<jats:p>Turfgrasses grown under low light conditions generally exhibit increased shoot elongation. Gibberellic acids (GAs), GA<jats:sub>1</jats:sub> in particular, promote stem elongation in grass species. GA<jats:sub>20</jats:sub> is the immediate precursor of GA<jats:sub>1</jats:sub>. However, a direct quantitative measurement of GA<jats:sub>1</jats:sub> and GA<jats:sub>20</jats:sub> has not been reported for turfgrass under different light intensities. This study was conducted in a greenhouse to quantify the endogenous levels of GA<jats:sub>1</jats:sub> and GA<jats:sub>20</jats:sub> of `KenblueTimes', `Livingston', and `NuGlade' Kentucky bluegrass (<jats:italic>Poa pratensis</jats:italic> L.) under two light intensities with and without trinexapacethyl (TE) application. GA<jats:sub>1</jats:sub> and GA<jats:sub>20</jats:sub> content in leaf tissue were analyzed using gas chromatography-mass spectrometry with deuterium-labeled GA<jats:sub>1</jats:sub> and GA<jats:sub>20</jats:sub> as internal standards. Light reduction of 73% under greenhouse conditions increased GA<jats:sub>1</jats:sub> by 44% to 47% and GA<jats:sub>20</jats:sub> by 16% to 50%. `NuGlade' had a GA<jats:sub>1</jats:sub> content 20% lower than that of `Kenblue', suggesting that the dwarf characteristics of `NuGlade' may be related to its low GA<jats:sub>1</jats:sub> content. The application of TE (0.1 kg·ha<jats:sup>-1</jats:sup>) reduced GA<jats:sub>1</jats:sub> concentration by 47%, but increased GA<jats:sub>20</jats:sub> concentration by 146%, supporting the contention that TE inhibited GA<jats:sub>1</jats:sub> biosynthesis by blocking the conversion of GA<jats:sub>20</jats:sub> to GA<jats:sub>1</jats:sub>. Chemical names used: 4-(cyclopropyl- -hydroxy-methylene)-3,5-dioxo-cyclohexanecarboxylic acid ethyl ester (trinexapac-ethyl); gibberellic acid (GA).</jats:p>

Ethephon and Trinexapac-ethyl Influence Creeping Bentgrass Growth, Quality, and Putting Green Performance

“…Trinexapacethyl (TE) 0 6.3 6.4 6.2 6.7 6.0 6.1 6.5 7.0 5.9 6.4 6.5 7.0 0.04 6.9 6.9 6.5 7.0 6.1 6.4 6.9 7.0 6.5 6. of gibberellin synthesis inhibition (16) and reduced TE efficacy has resulted in similar post-inhibition growth enhancements (PIGE) of Kentucky bluegrass (11). Ethephon suppressed weekly clipping yield 13 to 36% for 9 of the 12 weeks ( Fig.…”

“…Shoot growth recovered prior to the second and third applications, and clipping yields exceeded non‐TE‐treated turf by 13 to 35%. Accumulated GA 20 from TE use has been reported to increase ≈ 150% as a result of gibberellin synthesis inhibition (16) and reduced TE efficacy has resulted in similar post‐inhibition growth enhancements (PIGE) of Kentucky bluegrass (11). Ethephon suppressed weekly clipping yield 13 to 36% for 9 of the 12 weeks (Fig.…”

A Growing Degree Day Model to Schedule Trinexapac‐ethyl Applications on Agrostis stolonifera Golf Putting Greens

“…Influence of trinexapac-ethyl application rate and reapplication frequency on magnitude and duration of growth suppression in various turfgrass species. Reference McCullough et al, 2006aMcCullough et al, 2007Stier and Rogers, 2001Tan and Qian, 2003Beasley and Branham, 2007Gardner and Wherley, 2005Gardner and Wherley, 2005McCarty et al, 2004Stier and Rogers, 2001Richie et al, 2001Gardner and Wherley, 2005McCullough et al, 2007Fagerness and Yelverton, 2000Fagerness et al, 2004Qian and Engelke, 1999 ' Duration dependent on summer or fall season.…”

“…Trinexapac-ethyl suppresses clipping yield by inhibiting gibberellic acid (GA) synthesis through inhibition of GA 20 conversion to GA 1 , the bio-active gibberellin in cool-season turfgrasses (Reid and Ross, 1991;Rademacher, 2000). As a result, cell elongation decreases while GA 20 and total nonstructural carbohydrates (TNC) increase in concentration (Han et al, 1998(Han et al, , 2004Tan and Qian, 2003). These alterations reduce leaf length while mesophyll cell density, chlorophyll concentration, tiller density, and leaf area are enhanced (Ervin and Koski, 1998;Ervin and Koski, 2001;Stier and Rogers, 2001;Bunnell et al, 2005;Beasley et al, 2007).…”

Growth-active gibberellins overcome the very slow shoot growth of Hancornia speciosa, an important fruit tree from the Brazilian “Cerrado”

“…TNE is an acylcyclohexanedione with close structural similarities to 2-oxoglutarate, the essential co-substrate of soluble dioxygenases (2-ODDs) involved in the late stages of GA biosynthesis. Thus, TNE is assumed to competitively block late steps in the GAs biosynthesis Trees (2009) (Adams et al 1992;Griggs et al 1991;Rademacher 2000;Tan and Qian 2003). These late steps will not only include 3b-hydroxylation, the ''activation'' step, they will also include the ''inactivation'' step, e.g., inhibition of GA 2b-hydroxylation (Griggs et al 1991;Nakayama et al 1991).…”