Quantitative relationships between (a, b) the degree of leaf wounding and resulting average (± SE) integrated total BVOC (biogenic volatile organic compound) emission, and (c, d) maximum emission rate after leaf damage by (a, c) cutting or puncturing and (b, d) squeezing in Populus tremula. In (a) and (b), the integrated BVOC emission is the integrated estimate for 7 minutes after leaf wounding. In (a) and (c), black filled symbols correspond to lamina straight cuts and white filled symbols to leaf punctures. Total BVOC emission is the sum of emissions of all the 26 compounds measured (Table 1).