Growth of canola (Brassica napus) seeds treated with plant growth-promoting bacteria in copper-contaminated and polycyclic aromatic hydrocarbon (PAH)-contaminated soils was monitored. Pseudomonas asplenii AC, isolated from PAH-contaminated soil, was transformed to express a bacterial gene encoding 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and both native and transformed bacteria were tested for growth promotion. Inoculation of seeds, grown in the presence of copper or creosote, with either native or transformed P. asplenii AC significantly increased root and shoot biomass. Native and transformed P. asplenii AC and transformed P. asplenii AC encapsulated in alginate were equally effective at promoting plant growth in copper-contaminated soils. In creosote-contaminated soils the native bacterium was the least effective, and the transformed encapsulated bacterium was the most effective in growth promotion.

The inorganic carbon fixation patterns of Isoetes lacustris and Lobelia dortmanna from an oligotrophic Scottish loch have been examined by following titratable acidity changes in plant sap and light/dark CO incorporation by roots and shoots. The diurnal pattern of titratable acidity changes in I. lacustris suggests crassulacean acid metabolism (CAM) while the lack of any change in titratable acidity in L. dortmanna suggests C metabolism. Of the carbon fixed by L. dortmanna, 99.9% was taken up through the roots and fixation occurred primarily during the day. In Isoetes, CO was taken up by both roots and shoots and during both day and night. Regardless of the site of CO uptake, fixation occurred only in the shoots of both plants. Analysis of carbon isotope ratios of plant organic material was used to further investigate the photosynthetic mechanisms of these Isoetids. Considering the absence of a nighttime peak in titratable acidity in L. dortmanna, the ΔC (Δ=δC plant-δC source) value of the shoots of L. dortmanna (-14.2‰) is indicative of C photosynthesis limited by the rate of CO diffusion. The less negative Δ of I. lacustris (-6.0‰) is consistent with both dark acidification of CAM and CO limited C photosynthesis. This is in contrast to the terrestrial Isoetes durieui which is shown to have a Δ value which is similar to a terrestrial C plant. The carbon fixation patterns of these Isoetids suggest that the CO concentration in the loch may be growth limiting, and that root uptake and/or dark acidification are means of optimising CO supply. However, in view of the relatively high levels of CO in sediment and bulk water, it is suggested that low levels of nutrients may also limit growth in these plants.

Plant carbonic anhydrases (CAs) have a range of molecular weights (MW). Among flowering plants, dicotyledons with C3 photosynthesis have two isoenzymes of 140-250K each with 6 subunits, while monocotyledons have two isoenzymes of 42-45K. Plant and animal CAs have a similar amino acid content, subunit size and zinc content, suggesting they are homologous proteins, although the higher plant CAs have no esterase activity and are not strongly inhibited by sulfonamides. Algal CAs vary widely in MW and some are highly sensitive to sulfonamides like the animal enzymes. The two plant isoenzymes, from the chloroplast and cytosol, can be separated by gradient polyacrylamide gel electrophoresis and subsequently visualized by enzymic H+ ion production. In plants, CAs probably facilitate diffusion of CO2 to the site of photosynthetic fixation; they may also have a role in pH regulation, in the use of bicarbonate by aquatic plants and in concentrating inorganic carbon within the chloroplast.

Pinus radiata D. Don (half-sib families 20010 and 20062) and Pinus caribaea var hondurensis (an open-pollinated family) were grown for 49 weeks at seven levels of phosphorus and at CO2 concentrations of either 340 or 660 microliters per liter, to establish if the phosphorus requirements differed between the CO2 concentrations and if mycorrhizal associations were affected. When soil phosphorus availability was low, phosphorus uptake was increased by elevated CO2. This may have been related to changes in mycorrhizal competition. When the phosphorus concentration in the youngest fully expanded needles was above 600 milligrams per kilogram the shoot weight of all pine families was greater at high CO2 due to increases in rates of photosynthesis. whole plant level is that other factors, such as nutrient supply, may become limiting. In the majority of CO2 enrichment studies, the foliar nutrient concentrations have not been measured. Even when they were, the significance of the data is doubtful because the levels required to produce maximum growth at elevated CO2 have not been determined. However, a study with cucumber (Cucumis sativus) indicated that nutrient requirements may be increased by high CO2 (18). Nutrient availability is particularly relevant to the potential impact of atmospheric CO2 levels on tree growth because forests are typically restricted to infertile sites. P deficiency is of special interest because it eliminates the growth response to high CO2 in crop plants (9) and P. radiata (6).We report the growth of three Pinus genotypes (two halfsib families of P. radiata and an open-pollinated family of P. caribaea) at seven levels of P and at CO2 concentrations of either 340 or 660 uL CO2 L-'. Both the P. radiata families are known to produce more dry weight at elevated CO2 (7,8). Photosynthesis, sugar, and starch content of the needles and the level of mycorrhizal infection of the roots are also reported. The results clearly demonstrate increased P requirement of pines at elevated CO2. MATERIALS AND METHODS Plant CultureSoil was collected from a Pinus radiata plantation. It had a low level of available P and a high level of mycorrhizal inoculum. Other properties of this soil were previously described (8).There were ten pots for each of the seven P treatments planted with each Pinus family. Every pot contained 950 g of dry soil. P (CaHPO4) was added to the soil at the following rates (mg P kg-' soil): 0 (P0), 46 (P,), 92 (P2), 182 (P3), 274 (P4), 456 (P5), and 1368 (P6). Fertilizers other than P were added as previously described (6) and the soil and the fertilizers were mixed. Soluble P was added at 5 mg kg-' as NH4H2PO4 to all treatments at w2. Thereafter it was added on a regular basis to the P4, P5, and P6 treatments. N was applied as KNO3, Ca(NO3)2 .4 H20, Mg(NO3)2 .6 H20, (NH4)2SO4, and NH4NO3. The timing of these additions and the quantities of the various salts to be used were estimated from the fertilizer history and the chemical composition of the needles.

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