Eight cultivars of poinsettia, Euphorbia pulcherrima Willd., were evaluated for sensitivity to α-cyclopropyl-α (4-methoxyphenyl)-5-pyrimidine methanol (ancymidol) and protection from ozone and sulfur dioxide injury afforded by applications of ancymidol and (2-chloroethyl) trimethyl ammonium chloride (chlormequat). Foliar sprays of ancymidol were at least 80 to 500 times and the soil drench 1000 times more active than chlormequat in retarding stem elongation. The diam of the bracts was reduced, but branching increased more on plants treated with ancymidol than on untreated plants. The cv. Annette Hegg (AH) was more sensitive to ozone fumigations than was ‘Eckespoint C-l’ (C-l). Sulfur dioxide also caused more injury to AH than to C-l. Ancymidol and chlormequat reduced visible injury induced by ozone and sulfur dioxide.
Potted seedlings of white birch (Betula papyrifera Marsh.) and pin oak (Quercus palustris Muenchh.) were grown in the field for 3 months in relatively high- and low-ambient sulfur dioxide air. Biweekly throughout the growing season, plants from each site were harvested, and height and leaf, stem, and root dry weight were measured. The overall growth of white birch, an SO2-sensitive species, was found to be greater in the higher, but sub-phytotoxic SO2 environment. Conversely, the growth of pin oak, an SO2-tolerant species, was greater at the low SO2 site.
Pea (Pisum sativum L. ‘Alsweet’) plants were grown in a controlled environment and exposed to ozone, sulfur dioxide, or a mixture of the 2 pollutants. Plants were preconditioned with low (36%) or high (77%) relative humidity (RH) for 6 days and then exposed to the pollutants for 2 hr in low (31%) or high (67%) RH. Injury was evaluated as both necrosis and chlorophyll concentrations. A high RH prior to exposure to air pollutants greatly increased subsequent plant injury from pollutants. The increased injury with high RH prior to exposure to pollutants was associated with increased stomatal conductance. Relative humidity during exposure to air pollutants had little effect on plant injury.
Necrosis, chlorophyll concentration, dry weight and surface area measurements were made to evaluate injury to leaves of Pisum sativum L. cv Alsweet (garden pea) grown under controlled environments and exposed to sulfur dioxide, ozone and combinations of sulfur dioxide plus ozone. Injury evaluations were made at low pollutant levels causing slight necrotic injury and high levels causing severe necrotic injury. At low levels, expanded leaves with a trace of necrotic injury had a 10% reduction in chlorophyll concentration but no reductions in dry weight or surface area, while expanding leaves, also with a trace of necrotic injury, had a reduction in chlorophyll concentration accompanied by reductions in dry weight and surface area. At high pollutant levels, expanded leaves with severe necrotic injury had a 70% reduction in chlorophyll concentration and significant reductions in dry weight and surface area, while expanding leaves had a smaller amount of necrotic injury and a smaller reduction in chlorophyll concentration, but reductions in dry weight and surface area similar to those in expanded leaves. Thus, the following measurements are proposed as reliable indicators of injury at pollutant concentrations just above the threshold for injury: chlorophyll concentration for expanded leaves and surface area for expanding leaves. Reliable indicators of injury at higher concentrations causing serious injury to leaves are: necrosis for expanded leaves and chlorophyll concentration, dry weight, and surface area for expanding leaves.
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.
Reduced doses of sulfur dioxide (SO2) were evaluated for the fumigation of marine containers with respect to the concentration × time (CT) product and gas penetration. Two commercial export containers were loaded at 32 °F (0 °C) with 20 metric pallets [40 × 48 inches (102.5 × 123.1 cm)] comprised of 72 expanded polystyrene foam boxes (12 tiers, 6 boxes/tier) of table grapes (Vitis vinifera) and fumigated with 1.0 and 0.5 lb (0.454 and 0.227 kg) SO2, respectively. A third marine container was loaded with 20 metric pallets comprised of 84 plastic boxes of table grapes (14 tiers, 6 boxes/tier) and fumigated with 0.25 lb (0.113 kg) SO2. The boxes contained 16 lb (7.3 kg) of table grapes distributed in nine polyethylene cluster bagsenclosed in a perforated polyethylene box liner. Fumigations were performed through the bottom seal of the rear door from pre-weighed compressed SO2 cylinders. CT product was calculated after taking samples of the atmosphere in the container every 5 to 10 min and measuring the ambient SO2 concentration with a gas sampling pump and colorimetric dosimeter tubes. Pallet and box penetration of the gas was assessed by placing passive colorimetric SO2 dosimeters inside the cluster bags in boxes located in both the third and ninth center boxes from the top of pallets located in the front, center, and rear of the load. Fumigations with 1.0, 0.5, and 0.25 lb SO2, with calculated CT products at 32 °F of 925, 360, and 40 ppm-h (μL·L-1·h-1) respectively, were found to provide excessive, adequate, and insufficient SO2 doses.
immediately after harvest with sulfurdioxide gas followed by additional sulfurdioxide application during storage using either direct gas treatment or fumigation through continuous-release sulfurdioxide (SO 2 ) -generating pads. However, the concentration of
The sensitivity of 26 cultivars of tomato (Lycopersicon esculentum Mill.) were compared at 2 concentrations of SO2 in specially designed exposure greenhouses. Cultivars studied included fresh market, processing, and specialty types. Insensitive and sensitive cultivars were identified by assessment of acute SO2-induced foliar necrosis. Cultivars found to be insensitive to SO2 included: ‘Ace’, ‘Bonanza’, ‘Heinz 1350’, ‘Tarquinia Tondino’, and ‘VF 145-B 7879’. Cultivars found to be sensitive to SO2 included: ‘Bellarina’, ‘Chico IIP, ‘Flora-Dade’, ‘Red Cherry Large’, ‘SubArctic Delight’, and ‘Vetomold’.
‘Thompson Seedless’ grapes (Vitis vinifera L.) were fumigated with 0.5% SO2 at 0°C, and the amount of residual sulfite in the berries was followed over time. To prevent autooxidation during analysis, sulfite was stabilized using a solution of tetrachloromercurate-glycine, pH 10. After 72 hr, over 90% of the sulfite was oxidized to sulfate. Kinetics of sulfite loss indicate 2 different rates of loss, giving half-lives for sulfite of about 4 hr (70% of the total sulfite) and 20 hr (30% of the total sulfite). Presumably this reflects 2 forms, free and bound sulfite.
Mechanically harvested fruit of the strawberry (Fragaria × ananassa Duch.) cv. Veeglow destined for processing can be stored at 1°C in bulk bins for 4 to 6 days if room-cooled, and for 6 to 8 days if forced-air cooled promptly after harvest, without appreciable loss due to rot development or of quality of processed product. Yields of puree from fresh fruit mechanically harvested on day 8 of the storage trial were lower than for fruit that had been forced-air cooled and stored at 0° for 8 days. Sulfur dioxide fumigation immediately after cooling reduced losses due to rot and lowered mold counts, particularly when the fruit was room cooled.