The Physiological Action of Smog on Plants. I. Initial Growth and Transpiration Studies

Abstract

The effect of synthetic smog (1-n-hexene plus ozone) on growth and transpiration of tomato plants and on elongation of etiolated pea sections was studied. Use was made of hidden damage (growth decrease in the absence of visible injury) to measure the effects of light, sucrose spray, beta-naphthoxyacetic acid, and water supply on smog injury. Growth of tomato plants fumigated in the dark or light just following a 12-hr. dark period, or in the dark after 1.5 hrs. of light, was unaffected by smog. Growth of plants fumigated in the light at mid-day or early afternoon was significantly decreased by smog treatment. Sucrose spray partially protected tomato plants against smog damage. beta-Naphthoxy-acetic acid did not significantly affect the response of tomato plants to smog. Smog treatment did not affect the elongation of etiolated pea sections either in water or in 2,4-D soln. Tomato plants given limited water supply were resistant to smog damage while comparable plants receiving ample water were susceptible. Transpiration and water uptake rates of tomato plants were decreased by subjection to smog. The decrease was followed by recovery to slightly less than control rates. Subsequent fumigation caused repeated drops in transpiration rates followed by partial recovery. No direct correlation between stomatal opening and response of plants to smog was observed.