Inhibition of Net Photosynthesis in Tomato in Air Polluted with NO and NO2

Abstract

A 4 × 4 factorial experiment was conducted to examine the effects of air polluted with 0, 10, 25, and 50 parts 10⁻⁸ of NO and NO₂ on the rate of photosynthesis in tomato. Both gases reduced net photosynthesis to approximately the same extent, from a mean rate of 13·03 in the controls to 9·40 in 50 parts 10⁻⁸ NO and 8·84 in 50 parts 10⁻⁸ NO₂ (all values in mg CO₂ dm⁻² h⁻¹). There was no evidence of any interaction between the two pollutants, but their effects were nearly additive over parts of the concentration range tested. Tomato appears to be more sensitive to the presence of nitrogen oxides in the atmosphere than other species so far investigated. NO and NO₂ are generated by hydrocarbon burners used to provide CO₂ enrichment for glasshouses, and can accumulate in concentrations within the range employed in this experiment.