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Open access

L. Knudson Butler and T. W. Tibbitts

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.

Open access

P. M. McCool, J. A. Menge, and O. C. Taylor

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.

Open access

L. Knudson Butler, T. W. Tibbitts, and F. A. Bliss

Abstract

Ozone sensitivity was compared in F1 and F2 populations from crosses between 2 ozone-sensitive bean cultivars, ‘Spurt’ and ‘Blue Lake Stringless’, and 2 ozone-resistant cultivars, ‘Black Turtle Soup’ and ‘French’s Horticultural’, under controlled environmental conditions. F1 plants were as sensitive as the sensitive parent. About 10% of the F2 progeny obtained by selfing F1 plants appeared to be as resistant as the resistant parent and 90% of the progeny could be divided equally between a group as sensitive as the sensitive parent and a group intermediate in sensitivity between the parent plants. However, precise separation of F2 progeny was not possible because of the variability in injury expression. The average injury on the F2 plants was greater than the parental midpoint value and the variance in injury on the F2 plants was about 3.5x greater than that for the parents. The heritability of resistance to ozone was estimated to be 0.83. It was concluded that ozone resistance is recessive in P. vulgaris and appears to be regulated by a few major genes.

Open access

T. Elkiey, D. P. Ormrod, and R. L. Pelletier

Abstract

Under the light microscope the stomata of 3 cultivars of Petunia hybrida Vilm. were similar in shape and type. However, scanning electron microscopic examination of ‘White Cascade’ petunia (O3 sensitive) revealed guard cell cuticle was not raised above the epidermal surface. ‘Capri’ (O3 insensitive) had the greatest number of stomata/mm2 and the shortest pore length whereas ‘White Cascade’ had the lowest number but the longest pore length. The cultivar with intermediate O3 sensitivity, ‘White Magic’, had an intermediate stomatal density and pore size. The stomatal pore area (mm2/mm2 leaf surface area) was found to be about equal in all 3 cultivars. ‘Capri’ had many more trichomes per unit area than ‘White Cascade’ while ‘White Magic’ had intermediate numbers. No major differences existed in leaf diffusive resistance among the cvs. in either light or dark. The O3 insensitivity of ‘Capri’ was not explained by inherently fewer stomata and/or smaller stomatal size and/or greater leaf diffusive resistance than those of the sensitive ‘White Cascade’. Number of trichomes, sizes of epidermal cells and configuration of guard cell cuticle in relation to epidermal cells may be related to sensitivity.

Open access

J. T. A. Proctor and D. P. Ormrod

Abstract

American ginseng (Panax quinquefolius L.), was injured by exposure to 20 pphm ozone and/or 50 pphm (v/v) sulfur dioxide for 6 hr daily for 4 days. Ozone induced upper surface leaflet stippling along the veins and interveinaily, and sulfur dioxide induced mild chlorosis to irregular necrotic areas. Ginseng was less sensitive to ozone and as sensitive to sulfur dioxide as ‘Cherry Belle’ radish (Raphanus sativus L.) and ‘Bel W-3’ tobacco (Nicotiana tabacum L.).

Open access

B. R. Roberts and S. C. Domir

Abstract

Two-year-old containerized seedlings of American sycamore (Platanus occidentals L.) were treated with maleic hydrazide (MH) before, after, or in the absence of sulfur dioxide (S02) fumigation. Exposure to S02 did not reduce the effectiveness of MH in controlling regrowth of this species. A strong negative linear trend was observed between SO2 concentration and sprout growth, either with or without MH treatment. In all instances, exposure to 1.0 ppm S02 resulted in high levels of phytotoxicity.

Open access

T. E. Starkey, D. D. Davis, E. J. Pell, and W. Merrill

Abstract

Bean plants (Phaseolus vulgaris L. cvs. Provider and Stringless Black Valentine) were exposed to 395 µg/m3 (0.08 ppm) peroxyacetyl nitrate (PAN) for 0.5 hr and subjected to drought stress following exposure. PAN influenced the plant water potential of ΡAN-sensitive ‘Provider’ resulting in visible wilting and reduced soil moisture content. There was no effect of PAN on the water relations of the PAN-tolerant ‘Stringless Black Valentine’.

Open access

C. R. Johnson, J. N. Joiner, and D. N. Gower

Abstract

‘Shasta’ chrysanthemum (Chrysanthemum morifolium Ramat) showed less SO2-induced leaf necrosis than ‘Hurricane’. The growth retardant a-cyclopropyl-a-(4-methoxy-phenyl)-5-pyrimidine methanol (ancymidol) at 0.16 and 0.48 mg ai/2.5 cm pot reduced SO2 damage on both cultivars. There was positive correlation between stomatal activity (water diffusion resistance) and degree of leaf necrosis from SO2.

Open access

E. J. Pell and W. Gardner

Abstract

The response of ‘White Cascade’ and ‘Coral Magic’ petunia (Petunia hybrida Vilm. -Andr.) plants to peroxyactyl nitrate (PAN) was tested 7 days after application of soil drenches of 0, 20, 40, 60, 80, 100, 120 μg benomyl/g drv weight of soil. The susceptible ‘White Cascade’, showed increased sensitivity to 745 μg/m3 PAN for 1.5 hr when soil was treated with benomyl levels of 60 μ/g soil or greater. Enhanced foilar response to PAN was similar at all concentrations of benomyl greater than 60 μ/g soil. Foliage of ‘White Cascade’ petunias treated with concentrations of benomyl below 60 μ/g soil, responded to PAN similarly to plants which were not treated with the fungicide. The PAN sensitivity of the tolerant ‘Coral Magic’ was unaffected by benomyl application.

Open access

W. E. Hogsett, M. L. Gumpertz, S. R. Holman, and D. T. Tingey

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.