THE EFFECTS OF OXIDES OF NITROGEN AND CARBON-DIOXIDE ENRICHMENT ON GROWTH AND CONTENT OF RIBULOSE-1, 5-BISPHOSPHATE CARBOXYLASE-OXYGENASE AND NITRITE REDUCTASE IN GLASSHOUSE LETTUCE

Different systems of CO2 enrichment and heating were used to produce g lasshouse atmospheres with varying concentrations of NO(x) and CO2 (am bient NO(x) and CO2, ambient NO(x) and 1000 vpm CO2, and three concent rations of NO(x) varying between 0.5 and 2.5 vpm with concurrent CO2 c oncentrations between 1000-2500 vpm). The growth response of winter le ttuce in these environments was assessed for three contrasting cultiva rs (Ambassador, Berlo and Pascal). Contents of ribulose-1, 5-bisphosph ate carboxylase-oxygenase (RuBPco) and nitrite reductase (NiR) in the leaf tissue were also determined using immunoblotting and enzyme-linke d immunosorbent assay (ELISA). 'Ambassador' produced the heaviest ''he ad'' weights, but on marketable criteria 'Berlo' performed better. CO2 enrichment enhanced yields, but the High NO(x) treatments reduced gro wth relative to that in the Low NO(x) and unpolluted environments. Gro wth assessments suggested a greater tolerance of NO(x) in cvs Berlo an d Pascal than in cv. Ambassador. Immunoblots showed that the antibodie s used here were specific. Using these antibodies in ELISA, 'Pascal' w as found to contain more RuBPco and NiR on a leaf area basis than 'Amb assador'. There were reductions in RuBPco and NiR contents in response to growth in elevated CO2. Elevated CO2 caused a reduction in RuBPco and NiR in 'Ambassador', but in 'Pascal' only RuBPco levels were reduc ed. This may account for the greater relative tolerance of 'Pascal' an d the sensitivity of 'Ambassador' to NO(x) pollution.