Abstract
Seeds of tomato (Lycopersicon esculentum Mill.) and barley (Hordeum vulgare L.) on germination media were exposed to hydrogen chloride gas for 20 min. Seeds incubated and exposed on filter paper suffered developmental effects which were dependent on gas concentration. While germination rate was slightly reduced for sensitive seeds at the higher concentrations, suppression of seedling growth was evident at all levels of HCl tested. There was little effect on either germination or seedling length in seeds exposed and incubated on soil. Filter paper and soil adsorbed HCl during 20-minute exposures in proportion to gas concentration, but the soil apparently buffered most adverse reactions of the acid.
Abstract
Tomato plants (Lycopersicon esculentum Mill. cv. Bonny Best) grown in sand culture and provided with a complete nutrient solution or solutions containing sub- or supraoptimal Mg concentrations were fumigated with hydrogen fluoride (HF) at 5.0 or 9.7 μg F/m3 for 7 days. The severity of HF-induced chlorosis on apical and medial leaves was enhanced in Mg-deficient plants and suppressed in plants grown at the highest level of Mg. Foliar accumulation of fluoride (F) from exposure to the highest HF concentration was inhibited in plants provided the lowest and highest Mg levels. The presence of necrotic tissue probably suppressed the accumulation of F in Mg-deficient plants; however, it was not a factor in plants given supraoptimal Mg. The interactive effects of HF and Mg on foliar injury and F accumulation revealed that Mg-deficient plants were more susceptible and plants given excess Mg were more tolerant to HF than plants cultured on complete nutrient medium.
Abstract
Four cultivars of bean (Phaseolus vulgaris L.), with different sensitivities to ozone (O3), were exposed to chronic doses of O3 for 7 hr/day in early and late-season studies. Plants were pot-cultured in open-top field chambers. Greater than ambient O3 doses were applied by supplementing the O3 present in nonfiltered air with additional O3 at a constant rate for 7 hr/day. Cultivar sensitivity, as determined using an acute exposure screening protocol, was maintained in both studies. Regression of yield against O3 concentrations showed that ‘BBL-254’ and ‘BBL-290’ were more sensitive to O3 than were ‘BBL-274’ and ‘Dwarf Horticultural’. Results suggest that the acute screen used can predict the relative yield response of cultivars grown under field conditions when very sensitive and very resistant cultivars are compared. The results support the contention that bean germplasm has traits for resistance to O3 at current levels of O3, but that resistance is lost with increasing O3 concentration. Predicted relative yield suppression at a 7 hr/day seasonal mean of 0.04 to 0.06 ppm (the common ambient range in eastern United States) was 2% to 4% for the two resistant cultivars and 10% to 26% for the two sensitive cultivars.
Abstract
The ozone-sensitive bean cultivars ‘Spurt’ and ‘Blue Lake Stringless’ and the ozone-resistant cultivars ‘Black Turtle Soup’ and ‘French’s Horticultural’ were grown from seed in a growth chamber. The resistant cultivars had 25% fewer stomata per mm2 leaf area than the sensitive cultivars and exhibited partial stomatal closure following exposure to 134 pphm ozone for 1 hr, while the sensitive cultivars did not. Stomatal closure was determined to be more important than reduced stomatal frequency in providing resistance to ozone. On the basis of previously established ozone dose-response data for P. vulgaris, the stomatal mechanisms appeared to account for the difference in ozone sensitivity between the sensitive and resistant cultivars. Neither leaf area nor leaf expansion rate were correlated with genetic resistance to ozone in these cultivars.
Abstract
Nine conifer species, including 3 selections of Scotch pine, were exposed to SO2 dosages of 1310 µg/m3 (0.5 ppm) for 5 hours, 2620 µg/m3 (1.0 ppm) for 4 hours, or 5240 µg/m3 (2.0 ppm) for 2 hours. Seedlings in the cotyledon and primary needle stages were utilized throughout the study. Significant injury occurred only at the highest concentration. Pine species (Pinus spp) were more susceptible to SO2 than were spruce (Picea spp.), fir (Abies spp.) or Douglas-fir (Pseudotsuga sp.). The 3 Scotch pine selections and ponderosa pine were more susceptible than Austrian pine species. Balsam fir, Douglas-fir, Fraser fir, white fir, blue spruce, and white spruce were not injured.
Abstract
Spinach (Spinacia oleracea L.) was exposed intermittently to NO2 and SO2 (2 hours/week; 0.8 or 1.5 ppm) in a simultaneous or sequential fashion over the 42-day growth period. Nighttime simultaneous exposure to NO2 and SO2 reduced growth and altered assimilate partitioning to the root. The relative growth rate of total plant and root was reduced significantly below controls early in the growth period. In contrast, neither daytime exposure to the pollutant mixture nor sequential exposure to the 2 pollutants affected growth.
Abstract
Field plots of bean (Phaseolus vulgaris L. cv. Tendergreen) and tomato (Lycopersicon esculentum Mill. cv. Fireball 861 VR) were exposed for 43 and 99 days, respectively, to filtered ambient air or air containing hydrogen fluoride (HF) at a mean concentration of 0.6 µgF m-3. Comparisons between these treatments revealed that chronic exposure of bean to HF did not affect growth or induce foliar injury, whereas the fresh mass of marketable pods was reduced by almost 25%. There was no effect of HF exposure on growth or fruiting in tomato.
The combined effects of O3 and acid rain on freeze resistance, growth, and mineral nutrition were studied using broadleaf-evergreen citrus and avocado trees. Using a factorial design, `Ruby red' grapefruit (Citrus paradisi L.) trees on either Volkamer lemon (Citrus volkameriana Ten. & Pasq.) or sour orange (Citrus aurantium L.) rootstock and `Pancho' avocado trees (Persea americana Mill.) on `Waldin' rootstock were exposed to O3 and acid rain for 8 months in open-top chambers under field conditions. The O3 treatments were one-third ambient (0.3X), ambient (1X), twice ambient (2X), or thrice ambient (3X). Ambient O3 concentrations averaged 39.1 nl·liter-3 over a 12-hour day. The acid rain treatments had a pH of 3.3, 4.3, or 5.3 and were applied to simulate long-term rainfall averages. In general, the effects of acid rain on growth and freeze resistance were small. Rain of high acidity (pH = 3.3) offset the negative effects of O3 on growth (total leaf mass) in avocado and grapefruit/Volkamer lemon trees. In contrast, rain of high acidity magnified the detrimental effects of O3 on electrolyte leakage of leaf disks at subzero temperatures, especially for citrus. Freeze resistance, determined by stem and whole-plant survival following freezing temperatures, was lower in the most rapidly growing trees. Consequently, for trees exposed to a combination of O3 and acidic rain, leaf electrolyte leakage did not correlate significantly with stem survival of freezing temperatures. We conclude that the danger of acid rain to citrus and avocado in Florida is rather slight and would only present a potential problem in the presence of extremely high O3.
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.
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.