Epinastic response of potato to atmospheric ethylene near polyethylene manufacturing plants

Data of a multi-year (1984-1991) research programme performed at a test site in the vicinity of polyethylene manufacturing plants was analyzed to quantitatively assess the effect of atmospheric ethylene on epinasty in plants of potato. When the site was influenced by winds coming from the emission sources, hourly observations of the leaves indicated that epinasty occurred during circa 10% of the growing season on average and varied from circa 2% in 1985 to circa 31% in 1991. The epinastic response to ethylene was relatively high at night and low during the day and increased significantly with increasing pollutant concentrations and temperature, and decreased significantly with plant growth and increasing vapour pressure deficit. Regression of epinasty against hourly ethylene concentrations only revealed that 50 g m-3 ethylene corresponded with 5% epinasty and 70 g m-3 with 10% epinasty. These concentrations are higher than the threshold (12 g m-3) observed for phytotoxic effects of ethylene under laboratory conditions