Applicability of Pigment Compounds for Reducing Light Stress in Bentgrass

Chlorinated copper phthalocyanine (Signature) and pulverized cells of Chlorella vulgaris (Chlorella) were evaluated in a controlled environment for their ability to act as photoprotectants under supraoptimal levels of ultraviolet (UV) and photosynthetically active radiation (PAR) when applied to plant leaves. Plant pigment changes were documented using High Performance Liquid Chromatography following 1 week of exposure to supraoptimal light in two separate experiments incorporating UV (106.6 μmol m-2 s-1) and PAR (760.6 μmol m-2 s-1) over a 12h photoperiod. Supraoptimal levels of UV and PAR light were found to cause significant reductions in Agrostis palustris chlorophyll and carotenoid leaf pigment levels. In both experiments, high light coincided with increases in zeaxanthin and antheraxanthin and decreases in violaxanthin across all treatments, suggesting that plants experienced a stress response regardless of pigment application. Under high PAR light, the levels of total carotenoid pigment degradation were significantly higher in untreated Agrostis palustris controls than in Chlorella and Signature treated plants. However, only Chlorella demonstrated the ability to significantly reduce instances of chlorophyll degradation in bentgrass plants under high UV light.

Spectral imaging of light following transmission through treatments demonstrated how Chlorella was successful in limiting the absorbance of wavelengths in regions of UV (300 to 400 nm) and PAR (480 and 580 nm). Photon flux measurements of transmitted light showed a significant decrease in both treatments when compared to controls; the greatest reduction in light levels occurred with Chlorella applications under both UV and PAR light. Results of these experiments demonstrate how this interception of light may limit chlorophyll and carotenoid degradation under these conditions, suggesting that they may be used to successfully act as photoprotectants. This holds particular value in golf course maintenance, where bentgrasses are cultivated at low mowing heights in regions where supraoptimal light conditions persist throughout the growing season.