Effects of ozone on the regrowth and energy reserves of a ladino clover-tall fescue pasture.
A Trifolium repens cv. Regal and Festuca arundinacea cv. Kentucky 31 pasture was established in Sep. 1983 to determine the impact of O3 and available soil moisture on plants grown in open-top field chambers and exposed for 12 h daily to O3 (ranging from 0.57 to 2.00 times the av. seasonal concn in ambient air) from Apr. to Oct. in 1984 and 1985. Samples were removed periodically to measure above- and below-ground biomass and energy reserves. At final harvest (22 Oct. 1985), T. repens was the dominant species in below-ambient O3 (83% of total biomass; live roots + live shoots) while F. arundinacea was the dominant species at ambient and above-ambient O3 concn (95% of the total biomass). T. repens shoot and root biomass was reduced by O3 for all harvests when compared to plants grown in the charcoal-filtered air (0.30 µl O3/litre). Statistically significant O3 effects were observed on shoots prior to roots. Significant soil moisture effects were observed on shoot biomass only in July 1985. Significant moisture effects on root biomass were not observed until July and Aug. 1985. F. arundinacea shoot and root biomass production increased with increasing O3 levels for all but the final harvest. Significant moisture effects on shoot and root biomass were observed at various times in 1985. For most harvests, the energy reserves (starches) of T. repens roots were suppressed by increasing O3 concn. Shoot starch levels were not greatly affected by O3 or moisture. Energy reserves of F. arundinacea (starch and fructosan) were not affected by O3 or moisture. Total soluble sugars (glucose + fructose + sucrose) in both species were generally unaffected by O3 or moisture.