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BIOCHEMICAL EXPLANATIONS OF MORE THAN ADDITIVE INHIBITORY EFFECTS OF LOW ATMOSPHERIC LEVELS OF SULPHUR DIOXIDE PLUS NITROGEN DIOXIDE UPON PLANTS
Author(s) -
WELLBURN A. R.,
HIGGINSON CAROLYN,
ROBINSON DEBORAH,
WALMSLEY CHRISTINE
Publication year - 1981
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.1469-8137.1981.tb01719.x
Subject(s) - lolium perenne , lolium , phleum , dactylis glomerata , poa pratensis , biology , nitrate reductase , nitrite reductase , botany , agronomy , horticulture , nitrate , poaceae , ecology
SUMMARY Three clones of Lolium perenne L. known to show different sensitivities to SO 2 pollution, together with other grasses (Dactylis glomerata L., Phleum pratense L. and Poa pratensis L.), were fumigated with low levels of SO 2 , NO 2 and SO 2 + NO 2. Ratios of glutamate dehydrogenase activity (GDH) to that of glutamine synthetase (GS) were significantly raised by SO 2 (6·8 parts 10 ‐8 for 11 weeks) or SO 2 + NO 2 in the SO 2 ‐sensitive cloned cultivar S23 of L. perenne and by SO 2 + NO 2 in cloned Lolium perenne material which has high resistance to SO 2 (S23 Bell resistant). In Lolium derived from Pennine upland (Helmshore clone) GDH/GS ratios were unchanged in the presence of SO 2 or SO 2 + NO 2 but all three clones showed slight elevations in ratios in response to NO 2 fumigation alone. Within a week after treatment with NO 2 , all grasses had significantly higher nitrite reductase activities than similar plants given clean air, SO 2 or SO 2 + NO 2 treatments. The presence of SO 2 appeared to destroy the ability of the plant to respond to NO 2 , and this inhibition of a potential detoxification mechanism of nitrite is believed to be one of the main reasons why the SO 2 + NO 2 combination exhibits more than additive effects upon the growth of grasses. All three clones of Lolium perenne and also Phleum pratense showed enhanced ATP formation in the presence of low (6·8 parts 10 ‐8 for 20 weeks) levels of NO 2 , but reduced cyclic photophos‐phorylation in the presence of either SO 2 or SO 2 + NO 2. At higher levels of shorter duration (25 parts 10 ‐8 for 11 days), rates of ATP formation, ATP content and energy charge ratios were higher in NO 2 fumigated tissue than in controls, but lower in SO 2 + NO 2 treated tissue, although basic electron transport systems were unaffected. It is believed that the principal effect of the pollutant combination is upon proton gradients within the photosynthetic membranes leading to general deficiency in ATP which is necessary both for growth and the repair of secondary pollutant damage elsewhere. Parts 10 ‐8 (parts per hundred million) = quantity in μ m ‐3 × (1/mol. wt × 10 6 ) × 0·0224 × 10 8 at s.t.p. * for 11 weeks) or SO 2 + NO 2 in the SO 2 ‐sensitive cloned cultivar S23 of L. perenne and by SO 2 + NO 2 in cloned Lolium perenne material which has high resistance to SO 2 (S23 Bell resistant). In Lolium derived from Pennine upland (Helmshore clone) GDH/GS ratios were unchanged in the presence of SO 2 or SO 2 + NO 2 but all three clones showed slight elevations in ratios in response to NO 2 fumigation alone.