The Impact of Ultraviolet-B Light On Turfgrass Pigmentation and Physiology.

Reductions in the ozone layer have lead to predictions of increased ultraviolet-b (UV-B) light levels which may have many direct and indirect effects on plants, from DNA damage to reductions in biomass and alterations in transpiration and photosynthesis. Pigments offering light protective properties may play a crucial role in protection of chlorophyll and photosynthetic apparatus. The objective of this study was to characterize ultraviolet radiation damage to cool season grasses and to find out what plant responses occur. Four grasses were tested, creeping bentgrass Agrostis stolonifera L. ‘L-92’ and ‘Penncross’, tall fescue Schedenorus phoenix (Scop.) Holub and perennial ryegrass Lolium perenne L. Ultraviolet-b light (~20 kJ/m/d) and control treatments were initiated for 1,3,5 and 7 days. Turfgrasses were tested for impacts on fluorescence and chlorophyll pigment changes. Analysis of changes in flavonoids and phenols through the use of UV-Vis spectrophotometry occurred. Turfgrasses in the UV-B environment suffered significantly (P=0.05) more chlorophyll pigmentation decrease after 1 day. Higher levels of phenolics (P=0.05) were found in the top 5 cm, compared to roots or leaf tissue beneath the top 5 cm across all the grasses. Flavonoid levels varied within the plants similarly to the phenolics with the exception of Tall fescue which had similar levels in all tissue above ground. Ultraviolet light treatments resulted in a decrease in L-93 flavonoid levels and an increase in ryegrass quantities. The loss of quality was most visible on the bentgrasses with (P=0.05) poorer quality in UV-B light. Variations in pigment content and location may play a role in determining the quality response of a turfgrass to enhanced UV-B light conditions.