OZONE . EFFECT ON APPARENT PHOTOSYNTHESIS RATE OF TRANSPIRATION AND STOMATAL CLOSURE IN PLANTS

Little is known regarding the cause of plant growth suppression resulting from photochemical pollution. Studies with ozone indicate that elevated ozone concentrations may be involved. Ozone induced partial stomatal closure and a reduction in apparent photosynthesis and transpiration. High concentrations of ozone caused a temporary reduction in apparent photosynthesis of many species, often with little or no injury developing. The effect was reversible and plants frequently recovered within a few hours. Ozone concentrations as low as 10 p.p.h.m. for several hours caused partial stomatal closure of oats. A comparison of the effects of ozone under sunlight and artificial lighting showed that photosynthesis was reduced most in sunlight. © 1969, American Chemical Society. All rights reserved.