Search Results
Abstract
Premature fruit drop by navel oranges at an early stage of development is indicated to be one of the effects caused by photochemical air pollutants in the Los Angeles Basin (9). Both “weather fleck” of tobacco and “stipple” of grape leaves have also been shown by Heggestad and Middleton (3) and Richards, Middleton and Hewitt (8), respectively, to be caused by ozone, one of the members of the photochemical oxidant complex.
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
Marked differential injury by air pollution to a group of sweet corn hybrids in 2 experimental field plantings in the Los Angeles Basin occurred in 1969. At Riverside, leaf damage ranged from nearly zero in 11 hybrids to slight to severe in 23 others. Damage was clearly related to cultivar and was associated with periods of high oxidant levels and high maximum temperatures. There was only a slight relationship between the market maturity date of a cultivar and its degree of damage.
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
‘Troyer’ citrange [Poncirus trifoliata (L.) Raf. × Citrus sinensis (L.) Osbeck] seedlings were exposed to 82 ppm HCl for 20 minutes or 100 pphm ozone for 4 hours at 5, 12, and 16 weeks after inoculation with the vesicular-arbuscular mycorrhizal fungus, Glomus fasciculatus (Thaxter) Gerd. & Trappe. One group of citrange seedlings was exposed in a 2nd experiment to ozone at 90 pphm for 6 hours, once weekly, and a second group was exposed to 45 pphm for 3 hours, twice weekly for a period of 19 weeks beginning 1 week after fungal inoculation. Intermittent HCl and ozone exposures significantly reduced height and dry weight of mycorrhizal, but not of non-mycorrhizal plants. Fungal chlamydospore production was reduced 57% in ozone treatments but was not reduced by HCl exposures. Weekly exposures to 90 pphm ozone levels significantly reduced total dry weight in mycorrhizal plants by 42%, but reduced that of non-mycorrhizal plants by only 19%. However, 45 pphm ozone levels did not cause a similar reduction in either mycorrhizal or non-mycorrhizal plants. Mycorrhizal infection was reduced 15% and spore production 39% at 90 pphm ozone. The lower ozone level (45 pphm) reduced infection 22%, but had no effect on spore production. Absorption of phosphorus was not reduced by ozone treatments in either mycorrhizal or non-mycorrhizal plants.
Abstract
Greenhouse-grown root, foliage, fruit, and seed crops were exposed to peroxyacetyl nitrate (PAN) at 0, 5, 10, 20, and 40 ppb, 4 hours per day, twice per week, from germination to maturity of harvestable product. A response of PAN dose and growth or yield parameters was significant only for lettuce (Lactuca sativa L. cv. Empire) and Swiss chard (Beta vulgaris L. var. cicla, cv. Fordhook). Leaf fresh weight was reduced by 13% in ‘Empire’ lettuce and by 23% in chard in the 40 ppb PAN treatments relative to 0 ppb PAN controls. Peroxyacetyl nitrate at 10 ppb appeared to stimulate the growth of most crops. The threshold for inhibition of growth by PAN, under conditions of 2 exposures per week, appeared to be between 10 and 20 ppb. These results suggest that PAN, at concentrations below the threshold for visible injury, can alter the growth of plants, but that significant reductions in growth or yield may occur only in highly susceptible cultivars of leafy crops.
Abstract
A multiple regression analysis of yields of ‘6718 VF’ tomato (Lycopersicon esculentum Mill.) from 11 field plots along an ambient ozone gradient in southern California indicated that ozone was responsible for a significant reduction in fruit size. Ozone dose accounted for 85% of the reduction in fruit size and was at least 3.3 times more important than any of the monitored meteorological variables in predicting the percentage of marketable fruit. High ambient ozone depressed production and caused a significant decrease in fruit size over time. A model describing the reduction in marketing container yield (% reduction = 0 + (.0232 x dose)) predicted a 50% reduction at a dose of 2000 pphm-hours > 10 pphm.
Abstract
Foliar ozone sensitivity evaluations of 5 fresh market tomato (Lycopersicon esculentum Mill.) cultivars from fumigation experiments were contrasted with field trial yields at Riverside, California, a high ambient dose location (3798 pphm-hour > 10 pphm). Foliar injury was not an accurate indicator of yield response as a correlation of foliar susceptibility and yield rankings was insignificant. Cultivar production characteristics at the South Coast Field Station (222 pphm-hour > 10 pphm) and at Riverside were identical with standardized field plots of ‘6718 VF’ from a concurrent experiment. Reduced fruit size and depressed early season production, previously correlated with ozone dose, were characteristic of all cultivars planted at Riverside. Comparisons of cultivar production rankings revealed that ‘H-ll’ and ‘6718 VF’ yielded significantly more, in terms of weight and number of fruit harvested than ‘Ace’, ‘Polepak’, or ‘Earlypak 7’. All cultivars except ‘Ace’ produced equivalent yields in terms of weight at South Coast Field Station.