The Standardization of Poa Annua as an Indicator of Smog Concentrations. I. Effects of Temperature, Photoperiod, and Light Intensity during Growth of the Test-Plants.

Abstract

The environmental conditions in which Poa annua was grown had a strong effect on its smog sensitivity. A standardized strain was grown in 8 temp. conditions with various light intensities and photoperiods. At the 4 to stage, plants were given a single exposure to smog in a glass chamber with a regulated airflow and sufficient water supply. Measurement of damage in terms of % of damaged area per blade per plant, on 3 units of 10 plants each, gave statistically satisfactory results. Conditions producing high smog sensitivity were day temperature 26[degree]C, night 20[degree], with a 16 hour photo-period and slight shading when light intensity exceeded a daily average of more than 400 langleys. Low sensitivity was produced by temperature of day 30[degree]C, night 24[degree], or more. Sensitivity was strongly correlated with stomatal opening. Exposure to smog at about 450 foot candles (ft. c.) resulted in little damage; at about 1100 ft.c. damage was within 3% of that of plants exposed at 3500 ft.c. Good correlation between smog concentration measured chemically (total oxidants) and by plant damage, was found on days when light, temp., and duration of smog were comparable.