Light and CO2 Response Curves of Five Cool Season Turfgrasses.

The objectives of this experiment were to quantify photosynthesis and respiration rates of different turfgrasses at varying light levels and CO₂ levels, respectively, generating light and CO₂ response curves of common and novel turfgrasses. The hypothesis for this project is that tall fescue (Festuca arundinacea, Schreb.), velvet bentgrass (Agrostis canina, L.), Koeleria spp. and Deschampsia spp. will have higher photosynthesis rates under reduced light conditions than less tolerant species such as Kentucky bluegrass (Poa pratensis, L.) and creeping bentgrass (A. stolonifera, L.). This comparison has not been fully documented at present time and will be determined by comparing photosynthesis and respiration rates between species. Individual turfgrass plants were seeded into Cone-tainers™ and then allowed to mature for 18 wks in a greenhouse using a 16 hour photoperiod and temperature of 21-27°C. Irrigation was supplied once daily using an automatic system. Nitrogen was supplied through weekly foliar applications of liquid urea at 7 kg ha^-1 N. The growing medium was SunGrow Metro Mix 300. Photosynthesis and respiration rates were measured using a LiCor 6400 equipped with the single leaf chamber. Light response curves for each species were determined using 1400, 1100, 800, 500, and 200 umol m^-2 s^-1 photosynthetically active radiation (PAR), with light adjustments made using the red/blue light source of the leaf chamber. Respiration curves for each species were determined using 400, 200, 100, 50, 400, 600, and 800 umol mol^-1. Full results will be presented at the 2011 Annual Meetings.