Pigment Changes in Cool‐Season Turfgrasses in Response to Ultraviolet‐B Light Irradiance

Pigments and phenolics that absorb ultraviolet light (UV) are involved in the protection of the photosynthetic apparatus during periods of high ultraviolet‐B (UV‐B) radiation and can be of benefit to turfgrasses. This study initiated in October 2010 and repeated in March 2011 aimed to characterize protective pigment responses to elevated UV‐B in cool‐season turfgrass. Tall fescue (Festuca arundinacea Schreb.), perennial ryegrass (Lolium perenne L.), and creeping bentgrass (Agrostis stolonifera L.) cultivars L93 and Penncross were tested. Turfgrass pigment responses were measured over a 1‐wk period during which they were subjected to 16 kJ m−2 d−1 of UV‐B in growth chambers. Photoperiod was 14 h and plants were subjected to 26.2 mol m−2 d−1 photosynthetically active radiation (PAR) at 20° C day and 17°C night. Turfgrass samples were collected at Day 0, 1, 3, 5, and 7. Measurements included chlorophyll fluorescence, chlorophyll pigmentation, and flavonoid, phenolic, anthocyanins, and carotenoid concentrations. Chlorophyll fluorescence increased and chlorophyll quantities decreased significantly (P < 0.05) in UV‐B conditions compared to control. All species had significantly (P < 0.05) higher quantities of total phenolics and flavonoids at the top of the tissue canopy relative to roots and shoot tissue near the soil surface. Anthocyanins were only found in creeping bentgrass L93. Carotenoids, zeaxanthin, and β‐carotene declined in the UV‐B treatment for both creeping bentgrass L‐93 and Penncross after 7 d, but did not decrease for perennial ryegrass or tall fescue. Carotenoids may play a greater role in UV‐B tolerance than anthocyanins in cool‐season turfgrasses due to their ubiquitous presence.