Abstract:Seedlings ofnine tree species grown in pots were exposed to contamination enviroriment of sulphur and fluoride at Nanzhuang town,a ceramic industry area in Fushan city,Guangdong,and another part ofthe same plan ts were pored at South China Botanical Garden as contro1．The dry matter of seedling leaves was used to measure the gross caloric value by oxygen-bomb calorimeter．The ash content，ash-flee caloric value and the ratio of N and C were also determined．The results showed that the caloric values in Ilex rotunda,Machilus chinensis and Lysidice rhodostegia were relativelyhigh (above 19.O0 kJ g-1 )，and the values in Koelreuteria bipinnata, Ficus annulata, Michelia chapensis，Ficus microcarpa and Camellia semiserrata were lower(between 1 8.00-1 9.00 kJ g-1 )than the above three species，but higher than the value of athodea campanulata，which is lower than 1 8．00 kJ g-1．The air pollution stress caused the increase of gross caloric values in Koelreuteria bipinnata,Machilus chinensis and Ilex rotunda,but decrease ofthose in Lysidice rhodostegia, Michelia chinensis，Ficus microcarpa, athodea campanulat and Camellia semiserrata． However， the caloric values ofFicus annulata had only litle change between polluted and 1ess polluted environments． The analysis of Pearson correlation coefi cients showed that the ash-flee caloric value in leaves of the seedlings of 9 species did not significantly corelate with the C／N ratio and the ash content for coresponding species．However，the fluctuations of leaf caloric values in the same species under diferent environments were related to the pollution tolerance of the species，suggesting that the caloric value in leaves can be considered as an index of species sensitivity to air pollution．
