Abstract
Anatomical observations were made on 2 petunia cultivars of Petunia hybrida Vilm., one ozone and sulfur dioxide susceptible and the other moderately tolerant with leaf cross and paradermal sections made from collections taken 4 hours to 30 days following fumigation. Disintegration of the circular chloroplast bodies into one homogenous mass was the first visible symptom of internal cell damage. Initially, O3 affected chloroplasts in palisade cells while SO2 affected chloroplasts in spongy cells. Plasmolysis, aggregation of cytoplasmic contents, and disintegration of nuclei occurred. Damage from SO2 proceeded more rapidly and was more extensive than that from O3; all cell components were destroyed over larger areas. Foliar sprays of succinic acid-2,2-dimethyl-hydrazide (daminozide) or benomyl soil drenches were applied 1 week before fumigation. Microscopic observations indicated that mesophyll tissue in both daminozide and benomyl treatments resembled to some degree the compact tissue typical of young, insensitive leaves.
The effects of SO2 and NO2, singly and in combination, on the growth and physiology of nontuberizing Solarium tuberosum L. `Russet Burbank' plants were studied in controlled conditions. Plants were exposed to 0.11 μl SO2 and/or 0.11 μl NO2/liter for 24 hours a day up to 10 days. Statistically significant effects were observed mainly in the SO2+ NO2 treatments compared with the control plants. Leaf area was reduced from day 2 onward, and root fresh and dry weights were reduced from day 4 onward. Significant reductions in leaf and stem dry weights occurred on day 6. Net CO2 exchange rates were reduced for SO2 exposed compared with control plants beginning on day 3, while water loss rates were increased with SO2 + NO2 beginning on day 3. The increases in water loss rate were possibly due to the development of cuticular injury observed as abaxial glazing on the upper and middle canopy leaves. Leaf osmotic potential (π) of plants with SO2 + NO2 became more negative within the first 24 hours of the exposure. This reduction was accompanied by an increase in reducing sugar concentration. Xylem water potential was reduced in the mature and expanding leaflets by day 2 of the SO2 + NO2 exposure. The most sensitive aspect of the action of SO2 + NO2 appeared to be the increase in reducing sugars that affected osmotic potential in the leaves. Considering the retardation of root growth, these data suggest that the pollutant gases may have interfered with partitioning of dry matter from the leaves to the roots.
Two-year-old seedlings of red maple (Acer rubrum L.) were fumigated with SO2 (0.0, 0.5, 2.0, and 4.0 ppm) 8 hours daily for two 3-day periods spaced 3 days apart. Response to acute SO2 stress was determined by measuring changes in ethylene biosynthesis and membrane permeability. Ethylene evolution was a useful indicator of the onset of SO2 stress in red maple, but was not a particularly good indicator of the degree of stress. Membrane permeability was not as sensitive to the initial stages of SO2 stress, and significant changes in permeability were noted only at higher concentrations of this pollutant (> 2.0 ppm).
Abstract
Early-season ‘Perlette’, ‘Cardinal’, ‘Flame Seedless’, and ‘Thompson Seedless’ table grapes (Vitis vinifera L.) were fumigated at 21°C with methyl bromide (MB) at 32 g m−3 for 3.5 hours, SO2 (0.5% for 0.5 hours), or the 2 fumigants in sequence. Quality evaluations were made following holding at 2.5° for 6 days and again after an additional 2 days at 21°. SO2 fumigation reduced the percentage of rotten berries and the combination of SO2 and MB reduced the amount of bunch rot (Rhizopus rot). SO2 slightly bleached the color of the dark-pigmented grapes. Bromine residues in MB-fumigated and untreated grapes averaged 10.8 and 1.4 ppm, respectively.
Abstract
Hand- and machine-harvested ‘Stover’ (a white Euvitis hybrid) and ‘Noble’ (a red Vitis rotundofolia cultivar) grapes were either treated with 100 mg SO2/kg (applied as potassium metabisulfite, K2S2O5) or not treated and held at ambient temperature (≈25°C) for 0, 24, and 48 hr after harvest. Raw fruit and wine quality from each treatment were evaluated. ‘Noble’ grapes of all treatments held for 24 hr had developed signs of microbial spoilage, and the machine-harvested grapes held without SO2 had the most. However, only the machine-harvested ‘Stover’ grapes held without SO2 had began to deteriorate during 24 hr. Grapes of both cultivars had deteriorated after 48 hr, but SO2 limited the deterioration of both machine- and hand-harvested grapes. In general, machine-harvested grapes deteriorated to a greater extent than hand-harvested grapes. Wines made from ‘Noble’ grapes that had been held for 0 or 24 hr had similar quality, but machine-harvested ‘Stover’ grapes held for 0 to 24 hr without SO2 produced a poorer wine than the other treatments. Wines from machine-harvested grapes held for 48 hr had poorer quality than wines from hand-harvested grapes. Postharvest additions of SO2 improved the quality of wine from machine-harvested but not hand-harvested fruit held for 48 hr.
Abstract
Pollen tube growth of ‘Tilton’ apricot (Prunus armeniaca L.) was reduced by exposure to SO2. An empirical model, based on modified spline functions, described the decrease in pollen tube growth due to increasing dose (hours exposure × concentration of SO2) expressed on logarithmic scale. The response curve, based on this analysis, was “S-shaped” with a decrease from 98.5% pollen tube growth (PTG) for unexposed pollen tubes, based on percent of the style that the longest pollen tubes had grown to 91.6% at ℓ n dose 4.0. These was then a very sharp decrease in PTG to about 45% at ℓn dose 5.7, then a gradual curvilinear response to <1% PTG at the maximum ℓn dose of 7.7. There data strongly indicate that there is a threshold response to SO2 with respect to PTG. Response of ‘Van’ PTG in ‘Napoleon’ sweet cherry (P.avium L.) styles was similar to apricot, but not as definitive because of greater within year variation and differences between years. In one year (1979), a spline function model of PTG in cherry suggested a threshold value at about ℓn dose of 2.1, while in another year (1978), there was a nearly linear decrease in PTG with increasing ℓn dose.
Abstract
Comparative SO2 sensitivity was determined for red, pink, marble, and white cultivars of poinsettia, Euphorbia pulcherrima Willd. ex Klotzsch, belonging to 4 groups of sports: ‘Paul Mikkelsen’, ‘Annette Hegg’, ‘Eckespoint C-l’, and ‘Oakleaf’. Based on injury to the bracts, sports of the ‘Eckspoint C-l’ group were the most insensitive, whereas sports from the ‘Annette Hegg’ and ‘Paul Mikkelsen’ groups were the most sensitive. However, based on the number of leaves showing SO2 injury, sports from the ‘Oakleaf’ group were the most insensitive and those of the ‘Paul Mikkelsen’ group were the most sensitive. True leaves were generally much more sensitive to SO2 exposure than were corresponding bracts. There was no consistent relationship between bract color and extent of SO2 injury.
Abstract
Nine cultivars/selections of muscadine grapes (Vitis rotundifolia Michx.) were stored for 49 days at O°C in 6 liter telescoping, corrugated-cardboard shipping containers with polyethylene liners, and 3 types of commercially available SO2 generators. Susceptibility to decay during storage varied greatly among selections (7 to 82% decay without SO2). The SO2 generators produced up to 29 ppm SO2 and all 3 types reduced decay. The genotypes also varied widely in their tolerance of SO2. Placement of newspaper in the shipping containers reduced the concentrations of SO2, reduced SO2 damage to the fruit by up to 74%, and had an inconsistent influence on the development of decay. Fruit of selection NC 67A015-17 appeared to be the best suited for long-term storage.
Abstract
Potted plants of ‘Merit’ tomato (Lycopersicon esculentum Mill.) were grown from seed to maturity in controlled-environment chambers and exposed to charcoal-filtered air or 288-314 μgm-3 (0.11-0.12 ppm) SO2 during weeks 1-5, 6-10, or 1-10 beginning about one week after transplanting. Red ripe fruit harvested from plants exposed to SO2 exhibited a slight but significant decrease in ascorbic acid expressed on a dry-weight basis. SO2 induced significantly greater levels of foliar sulfur, but did not increase sulfur content of the fruit. Exposure of plants to SO2 did not affect fruit yield or quality factors including soluble solids, total solids, or ascorbic acid on fresh-weight basis. A multiple regression model revealed low but significant R2 values, indicating a weak and indirect, yet significant, association between plant sulfur content and fruit ascorbic acid.
Watermelon, Citrullus lanatus (Thunb.) Matsum & Nakai cv. Sugar Baby, were grown in the field as a fall crop in open-top chambers (OTC) in southwestern Indiana with either charcoal-filtered (CF) or nonfiltered (NF) air. Ozone and sulfur dioxide were continuously monitored in OTC and ambient air. There was a significant decrease in marketable yield by weight (19.9%, P = 0.05), percentage of marketable fruit by number (20.8%, P = 0.10), and total yield by weight (21.5%, P = 0.05) from plants grown in the NF air treatment compared with those grown in CF air. Ozone-induced foliar injury was significantly greater on plants grown under NF conditions. Ambient concentrations of 03 in southwestern Indiana caused foliar injury (P = 0.10) and significant yield loss to a fall crop of watermelons.