Civitas Alters Turfgrass Transpiration and Photosynthetic Capacity.

A novel horticultural oil Civitas™ has been found to increase turfgrass clipping yield and disease resistance following phytotoxicity in field trails.  However, a clear understanding how Civitas affects turfgrass physiology is lacking.  Several studies were conducted to quantify net photosynthesis, transpiration, and nonstructural carbohydrate reserves following Civitas application to turfgrass.  Studies were conducted in a growth chamber at Cornell University on three month old Poa annua plugs.  The plugs were established in 38mm diameter cone-tainers, clipped to 15mm, and irrigated daily.  Treatments in the first study included a control, Civitas alone, and Civitas with a green pigment.  Treatments contained an equivalent amount of Civitas, 5.1 mL m^-2.  During the second experiment, Civitas was applied alone at 0, 1.2, 2.6, 5.1, and 10.2 ml m^-2.  All applications were made with a CO₂ powered backpack sprayer equipped with TeeJet AI 8004 nozzles at 80 mL m^-2 spray volume and were replicated seven times.  A Licor 6400 photosynthesis meter with Arabidopsis chamber was used to measure net photosynthesis and transpiration at various light intensities from 0 to 2000 µmol PAR m^-2 s^-1 and constant humidity.  CO₂ responsiveness was also measured from 50 to 600 ppm in this study.  Measurements were taken 3 hours, 1, 2, 5, and 10 days after application.  Repeated measures analysis in JMP was used for data analysis.  Both the Civitas and Civitas-pigment mixture reduced transpiration and net photosynthesis at light intensities greater than 750 µmol PAR m^-2 s^-1.  Maximum estimated respiration was not affected by either Civitas treatment.  The CO₂ response curves suggest inhibition via diminished stomatal conductance and is supported by micrographs of stomata.  There was a significant application rate effect; net photosynthesis and transpiration were further suppressed at increased application rates.