Abstract
Tomato seedlings (Lycopersicon esculentum Mill. ‘Heinz 1350’) were inoculated with the vesicular-arbuscular mycorrhizal fungus Glomus fasciculatus (Thaxter) Gerd. & Trappe and either exposed to 30 pphm (589 μg/m3) ozone or to filtered air for 3 hours once weekly, beginning 3 weeks after inoculation, under long photoperiods (12–13.5 hr). Root infection by G. fasciculatus in ozone-exposed plants was retarded from week 3 to 5 compared to controls but recovered by week 7. Growth rates of mycorrhizal control plants were significantly greater than ozone-exposed mycorrhizal plants, but there were no differences in growth rates of nonmycorrhizal controls, mycorrhizal ozone-exposed plants, and nonmycorrhizal ozone-exposed plants. Under short photoperiods (less than 12 hr), growth rates of mycorrhizal controls were less than nonmycorrhizal controls and ozone did not significantly affect growth rates of nonmycorrhizal plants relative to controls. Leaf chlorophyll levels were similar whether plants were mycorrhizal, nonmycorrhizal, or exposed to ozone.
Abstract
Three cultivars of greenhouse-grown apple trees (Malus domestica, Borkh.) were fumigated for single, 4-hour exposures with ozone (O3) and/or sulfur dioxide (SO2) at 0.40 and 0.80 ppm. Fumigations were performed in a plexiglass chamber situated within a controlled environment walk-in growth chamber. All 3 cultivars responded to treatments in a similar manner. When applied separately both gases induced characteristic foliar injury. In general, apple trees were more sensitive to 0.40 ppm O3 than to 0.40 ppm SO2; but they responded similarly to 0.80 ppm O3 or SO2. Foliar injury, leaf abscission, and shoot growth reduction were greatest when 0.80 ppm O3 and 0.80 ppm SO2 were combined. The data showed a less-than additive response when the 2 pollutants were combined; a response due, in part, to the high amount of injury induced by single pollutants at these concentrations. All O3 and/or SO2 fumigations resulted in stomatal closure.
Abstract
The inheritance of peroxyacetyl nitrate (PAN) resistance in Petunia hybrida Vilm. was studied using the inbred parents of ‘White Cascade’, a susceptible F1 hybrid, and ‘Coral Magic’, a resistant hybrid. In each of 6 experiments, 4-week-old plants of the parents, their reciprocal F1 hybrids, the F2 generation, and reciprocal backcross generations were simultaneously tested for PAN resistance. Plants were exposed to 742 μg/m3 (0.15 ppm) PAN for 1.5 hours in a controlled environment chamber. The percent area of bifacial necrosis was determined for each leaf on a plant and an average was calculated to yield an injury rating. Significant genetic variation was detected in each experiment, but the best fitting genetic model varied among experiments, indicating large genotype by environment interaction. In the experiment with the most severe PAN injury, genes for susceptibility exhibited almost complete dominance to those for resistance and epistatic effects were not significant. In other experiments with lower levels of PAN injury, resistance was partially dominant to susceptibility and one or more epistatic parameters were significant.
Abstract
The relative ozone sensitivities of a 7-parent diallel set of petunia hybrids were compared with their rates of ozone absorption, rates of transpiration, ascorbic acid concentrations, and shoot and root weights. Ozone sensitivity was highly correlated with both ozone and water vapor diffusion resistance, but not with ascorbic acid concentration or shoot-root ratio.
Abstract
Container-grown plants of carrot (Daucus carota L.) exposed intermittently to 0.19 or 0.25 ppm ozone throughout their growth increased in plant height and total number of leaves in spite of the development of chlorotic leaves. Leaf dry weight was unaffected by ozone, but root dry matter decreased 32 to 46%. As a result, the root weight/total dry weight ratio and root/shoot ratio declined significantly in the presence of ozone. A regression of root dry weight on chlorotic leaf dry weight explained 35% of the root loss and predicted that 1.5 g of root tissue is lost for every g of chlorotic leaf dry weight caused by ozone injury.
Abstract
The capacity of rhododendron (Rhododendron catawbiense Michx., cv. Nova Zembla) and firethorn (Pyracantha coccinea M. J. Roem. var. Lalandii (Duren) Dipp.) to change ambient SO2 levels in a closed fumigation system was studied. P. coccinea removed greater quantities of SO2 at faster rates than R. catawbiense. Differences in leaf surface characteristics between the 2 species suggest that at least part of the SO2 uptake mechanism may involve a surface-mediated response to the pollutant.
Abstract
[N-[2-(2-oxo-l-imidazolidinyl)ethyl]-N’-phenylurea (EDU or ethylenediurea) was applied as a soil drench and as foliar sprays to evaluate protection from ozone injury in controlled fumigations on 44 species of herbaceous plants. At least 4 doses of EDU were compared on 5 plant species: Begonia cucullata var. Hookeri Willd., (fibrous rooted begonia), Tagetes erecta L. (marigold), Antirrhinum majus L. (snapdragon), Lycopersicon esculentum Mill, (tomato), and Chrysanthemum morifolium Ramat. (chrysanthemum). Protection from ozone injury was directly related to EDU dose up to about 500 ppm. The spray and drench treatments gave about the same protection from ozone. EDU had no measurable effect on plant growth. Genera showing relatively high sensitivity to ozone and good protection with EDU included Ageratum, Amaranthus, Browallia, Capsicum, Celosiay Dahlia, Lobelia, Lycopersicon, Nicotiana, Perilla, Salvia, and Zinnia. The EDU treatments used did not protect adequately Hedera Lactuca, Rosa, or Zea mays (sweet corn). Species of several genera showed little or no foliar injury even at the highest ozone dose (0.60 ppm/3 hr), including Brassaia, Catharanthus, Chlorophytum, Coffeay Cyclamen, Dizygotheca, Philodendron, Saintpaulia, and Torenia. ‘Fred Shoesmith’ chrysanthemum was insensitive to ozone.
Abstract
Eight cultivars of azalea were tested for sensitivity to 0.25 ppm of nitrogen dioxide (NO2), sulfur dioxide (SO2) and ozone (O3), alone and in mixture. Sixty-eight days after pruning, the 1 yr-old liner plants were exposed to the pollutants for 6, 3-hr fumigations over a 4 week period. Cultivars demonstrated a range of sensitivity (tolerant to moderately sensitive) based on both visible injury and growth. Neither NO2 nor SO2 (alone and in combination) induced foliar injury on any of the cultivars. Ozone and mixtures of O3 with NO2 and/or SO2 induced small amounts of injury (10% or less) to foliage of ‘Pink Gumpo’, ‘Mme. Pericat’ and ‘Red Wing’. ‘Red Luann’, ‘Glacier’, and ‘Hershey Red’, sustained >10% foliar injury from mixture treatments containing O3. No significant interactions among NO2, SO2, and O3 were detected by measurements of plant weight. The pollutants did not change the weight of leaves or stems of ‘Pink Gumpo’ and ‘Mme. Pericat’. Significant weight loss occurred in leaves or stems from exposure of ‘Hershey Red’, ‘Red Luann’, and ‘Red Wing’ to treatments containing O3 and from exposure of ’Mrs. G. G. Gerbing’, ‘Glacier’, and ‘Red Luann’ to treatments containing SO2.
Abstract
Transpiration rate, stem diameter, and leaf temperature of satsuma mandarin (Citrus unshiu Marc.) were found to be sensitive indicators of stomatal response to ozone exposure. Time of reaction of each to 1.2 ppm ozone was 3 min. Stem diameter showed marked oscillation and leaf temperature slight oscillation, when ozone was applied. Correlation coefficiennt between ozone concentration and transpiration rate at the equilibrium status after the beginning of exposure was r = 0.718, and increasing the concentration of ozone decreased stomata size. Thus, it was determined that low sensitivity of satsuma mandarin to ozone is due to rapid stomatal closure by ozone.
Abstract
Eighteen bean cultivars were grown from seed in a growth chamber and exposed to 140 pphm ozone for 1 hr. ‘Sanilac,’ ‘Tenderette,’ ‘Blue Lake Stringless,’ ‘Bush Blue Lake 290,’ and ‘Spurt’ were the most sensitive to ozone; ‘Pinto 111’ was moderately sensitive; and ‘Black Turtle Soup’ and ‘French’s Horticultural’ were the most resistant. Necrotic flecking, dispersed over most of the leaf, characteristically developed on the cultivars ‘Spurt,’ ‘Early Gallatin,’ ‘Orbit,’ and ‘French’s Horticultural.’Necrotic patching, restricted to certain areas of the leaf, characteristically developed on ‘Sanilac,’ ‘Blue Lake Stringless,’ ‘Bush Blue Lake 290,’ ‘Bush Blue Lake 274,’ ‘Apollo,’ ‘Coloma,’ ‘Tempo,’ and ‘Black Turtle Soup.’ Pigmented lesions on adaxial surfaces developed on all ‘Sanilac’ plants and on some ‘Resistant Asgrow Valentine’ and ‘Pinto 111’ plants. A generalized chlorosis was observed on some plants of all cultivars. Cultivar sensitivity was evaluated by determination of chlorophyll concentration and visual observations. For most cultivars, similar estimates of injury were obtained by the 2 methods. Injury assessments differed the most for cultivars that developed the necrotic patching symptom.