Pigment Concentrations among Heat-tolerant Turfgrasses

Heat-tolerant bluegrass varieties were developed to resist dormancy and retain pigmentation during heat stress events. The objective of this study was to investigate the influence of grass species, nitrogen (N) fertilization, and seasonality on the accumulation patterns of lutein, β-carotene, and chlorophyll a and b in the leaf tissues of turfgrass. The heat-tolerant bluegrass cultivars Dura Blue and Thermal Blue (Poa pratensis L. x Poa arachnifera Torr.), Apollo kentucky bluegrass (Poa pratensis L.), and Kentucky 31 tall fescue (Festuca arundinacea Schreb.) were compared for the accumulation of plant pigments. Evaluations were conducted over 2 consecutive years (Years 4 and 5 after establishment) during two different seasons (spring and summer) and under varying N fertilization. Fertilizer applications of 5, 14, and 27 g N/m²/year resulted in a significant positive correlation for the accumulation of leaf blade lutein and chlorophyll a and b, but not for β-carotene. The accumulation of the four measured plant pigments among the grasses was significantly different with ‘Apollo’ having the largest concentration of pigments followed by ‘Dura Blue’, ‘Thermal Blue’, and finally ‘Kentucky 31’. Specifically, when comparing the cultivars Apollo and Kentucky 31, the pigment levels decreased 27%, 26%, 26%, and 23% for lutein, β-carotene, and chlorophyll a and b, respectively. The interesting observation of the analysis of the grass pigment concentrations was that the least reported heat-tolerant cultivar in our study (‘Apollo’) had the largest measured pigment concentrations.