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THE INFLUENCE OF SO 2 AND NO 2 ON THE GROWTH, DEVELOPMENT AND GAS EXCHANGE OF BETULA PENDULA ROTH
Author(s) -
FREERSMITH P. H.
Publication year - 1985
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1985.tb03669.x
Subject(s) - betula pendula , shoot , horticulture , chemistry , pollutant , dormancy , phytotoxicity , botany , dry weight , zoology , biology , germination , organic chemistry
S ummary SO 2 and NO x are main primary pollutants which often occur together in Europe. In three experiments, Betula pendula Roth, was exposed to SO 2 and NO 2 , at concentrations of between 30 and 90 nl l −1 , in controlled conditions during the first year of growth. In addition, single plant chambers were used to examine the net fluxes of SO 2 to the shoots. The effects of continuous exposure to this range of concentrations of SO 2 + NO 2 varied from a 20% increase to a 32% decrease in total dry weight. This contrast of responses came about because the doses of pollutant and light conditions were altered. Foliar injury and subsequent decreases of growth occurred when exposure concentrations exceeded 70 nl l −1 of both gases, although the onset of dormancy influenced the responses which were observed. Premature loss of leaves was the main symptom of chronic injury‐ in SO 2 and the threshold concentration for this effect was about 50 nl l −1 . When grown in conditions of poor light B. pendula made changes of partitioning so that leaf growth was favoured, and also showed greater phytotoxic effects as a result of exposure to SO 2 and SO 2 + NO 2 . In conditions of large PFD and longdays the toxic effects of SO 2 were lost so that significant interactions in the effects of SO 2 and photoen vironment were detected. SO 2 also caused decreases in root–shoot ratio and increases in LAR but NO 2 did not influence partitioning in this way. Stomatal conductance was influenced by fumigation with 40 nl l −1 SO 2 and there were slight decreases of net photosynthesis in the presence of 55 nl l −1 SO 2 . The rates of deposition of SO 2 were largely controlled by stomatal conductance and no emission of H 2 S was detected. Cuticular deposition of SO 2 varied, making up between 11 and 25% of the total flux and becoming of greater importance as the stomata closed.