Ecophysiological Responses and Sensitivity of 39 Woody Species Exposed to Air Pollution

Abstract:

This study aims to test the sensitivity of thirty-nine 1 to 2-year-old woody species planted in pots and exposed to heavily polluted and relatively clean sites for 5 months during growing season in Nanhai, Foshan, Guangdong Province. Evaluation on possible effects of air pollution on plants and their acclimation strategies were made on the basis of gas exchange measurements using LCA-4 photosynthesis system. Air monitoring data showed that the polluted area received remarkably higher sulfation rate, fluoride concentration and total suspended particles than the clean site, which significantly exceed the emission limit of National Standard. Net photosynthetic rate(P_n), transpiration rate(E), stomatal conductance (g_s) differed among species and decreased for most species in the polluted area. Pooled data showed that P_n and E were linearly correlated with g_s to some extent at the relative clean site and polluted area, suggesting that most species showed possibility to adapt the pollution stress by simultaneously controlling photosynthesis and transpiration. The correlation of the P_n with g_s (or E with g_s) had been weakened (or enhanced) under pollution stress, which demonstrated the unparallel and complexity in changes of P_n and E with g_s, and the diversity of acclimation strategies among different species. Based on the change in P_n, E and water use efficiency (WUE), plants can be ranked as follows by their sensibilities to air pollution, species that exhibited high sensibility included Lysidice rhodostegia, Manglietia glauca, Erythrophloeum fordii, Altingia chinensis, Artocarpus hypargyreus, Manglietia hainannensis, Aquilaria sinensis and Ormosia pinnata; species showing moderate sensitivity were lieritiera parvifolia, Magnolia delavayi, Fagraea ceilanica, Manglietia insignis, Artocarpus styracifolius, Heteropanax fragrans, Saraca chinensis, Machilus saclicina, Annona muricata, Ternstroemia gymnanthera, Dolichandrone cauda-felina, Artocarpus nitidus subsp. lingnanens, Cassia fistula, Camellia semiserrata, Tsoongiodendraon odorum, Osmanthus fragrans, Ilex rotunda, Elaeocarpus japonicus, Spathodea campanulata, Mesua ferrea, Myrsine seguinii; and those showing low sensibility were Actinodaphne pilosa, Machilus chinensis, Kigelia Africana, Gordonia axillaries, Camellia japonica, Ficus mucrocarpa var. fuyuensis, Ficus microcarpa, F. annulata, F. religiosa and Tutcheria spectabilis.