Patrick J. Temple

Foliar injury responses of ponderosa pine seedlings to ozone, wet and dry acidic deposition, and drought

Abstract A 3-year field study of the potential interactions of ozone (O3), wet and dry acidic deposition, and soil water availability on foliar injury responses of 18 ponderosa pine (Pinus ponderosa Laws.) families was conducted in the Sierra Nevadas of California. Thirty-six 2-year-old seedlings in each of 30 open-top chambers (plus six ambient air plots) were exposed to combinations of three levels of O3 [charcoal-filtered (CF), non-charcoal filtered (NF), and NF plus 1.5 times ambient O3 (NF150)]; three simulated rain pH treatments (pH 3.5, 4.4, 5.3); two levels of dry deposition (60% filtration of ambient dry deposition and 90% filtration), and two irrigation regimes (approximately weekly watering vs irrigation every other week) for three growing seasons. One-third of the trees were harvested at the end of each year. O3, irrigation level, amount of dry deposition, and family (genotype) significantly affected degree of foliar injury responses to O3. The interactions of O3 with irrigation amount and O3 with dry deposition were also statistically significant. Drought-stressed seedlings had significantly less O3 injury than well-watered trees, but seedlings exposed to 60% filtration of dry deposition had significantly greater O3 injury than those in the 90% filtered treatments. Ponderosa pine families differed greatly in susceptibility to O3, ranging from two with an average of > 20% O3 injury to several with nearly no O3 injury. These results reflect the complex patterns ofponderosa pine responses to natural and pollutant stresses and emphasize the importance of long-term, multifactorial experiments to elucidate those patterns.

Injury and growth of Jeffrey pine and giant sequoia in response to ozone and acidic mist

Abstract A 2-year study of the interactive effect of sequential exposures of Jeffrey pine ( P. Jeffreyi ) and giant sequoia ( S. giganteum ) to simulated acidic mist and ozone (O 3 ) was conducted in 1985 and 1986. Two-year-old seedlings of each species were exposed to simulated mist acidified to pH 4.1, 3.4, 2.7 or 2.0 with 2:1 HNO 3 /H 2 SO 4 plus appropriate background ions 3 days per week from 0300 to 0600 in outdoor mist exposure chambers. On the same day the same plants were exposed to 0, 0.10 or 0.20 ppm O 3 from 1200 to 1600. Exposures were conducted in May and June of each year. Each O 3 × pH combination contained 12 plants of each species and each treatment was replicated twice. Half the trees were harvested after the first year and the rest after 2 years of exposure to O 3 and simulated acidic mist. In the first year, O 3 at both 0.10 and 0.20 ppm caused light to moderate chlorotic mottle on Jeffrey pine but O 3 had no effect on giant sequoia. Simulated mist at pH 2.0 caused severe foliar necrosis on both species. Ozone had no significant effect on growth of either species in 1985, but simulated acidic mist at pH 2.0 significantly reduced growth of both species. In 1986, similar visible foliar injury symptoms were observed on both species. Ozone significantly reduced leaf, stem and root growth of Jeffrey pine, but growth of giant sequoia was not affected by O 3 . Exposure to simulated acidic mist stimulated Jeffrey pine growth at intermediate pH (3.4 and 2.7) and significantly reduced growth at pH 2.0, relative to growth at pH 4.1. Simulated acidic mist significantly reduced root growth of giant sequoia, particularly at pH 2.0, and the combination of O 3 at 0.20 ppm and mist at pH 2.0 reduced sequoia root growth significantly more than the additive effects of either pollutant acting alone. The effects of both pollutants on root growth were attributed to reallocation of photoassimilates from roots to shoots to maintain growth of photosynthetic tissues.

Acid mist and ozone effects on the leaf chemistry of two western conifer species

Seedlings of Jeffrey pine (Pinus jeffreyi) and giant sequoia (Sequoiadendron gigantea) were more susceptible to leaf chemical changes following exposure to acid mist (pH 3.4-2.0) or acid mist/ozone combinations, than to ozone alone (0.1-0.2 microl/litre), when plants were exposed to alternating doses of these pollutants for 6-9 weeks. Under acid mist treatment, leaves exhibited higher levels of nitrogen and sulfur, two elements applied in acid mist. In addition, levels of foliar sodium, and, in the case of giant sequia, potassium, as well, increased under acid mist treatment. Iron and manganese were also mobilized, resulting in significant increases in these elements in pine, and decreases in manganese in giant sequoia foliage. The acid treatment also reduced chlorophyll b concentrations in pine, and, to a less significant extent, in giant sequoia. Calcium, magnesium, barium and strontium were differentially accumulated in giant sequoia compared to Jeffrey pine. Under acid mist treatment, all of these elements (except strontium) declined in concentration in giant sequoia, with calcium showing the most significant trend. The more extensive changes in leaf chemistry induced by acid mist are consistent with earlier observations of significant changes in spectral reflectance of these seedlings after 3 weeks of fumigation. Limited foliage samples collected from these two species in 1985 and 1986 in Sequoia/Kings Canyon National Parks in the southern Sierra Nevada do not in themselves indicate any clearcut or severe effects of ozone alone on leaf chemistry of these species, but a mild influence of nitrate-laden acid deposition, possibly in combination with ozone, is consistent with the rise in nitrogen and lignin levels in Jeffrey pine on sites observed to have moderate visible injury symptoms. No firm conclusions about effects of pollutants on leaf chemistry in these field sites is possible without further study.

Growth and yield responses of processing tomato (Lycopersicon esculentum Mill.) cultivars to ozone

Abstract Dose-response equations relating exposure to an air pollutant with yield losses in crops are essential elements in economic assessments of the impacts of air pollution on agriculture. However, dose-response equations for some crop species, such as tomato (Lycopersicon esculentum Mill.), are based upon research with a single cultivar, which may or may not represent the response of the species as a whole. This experiment was conducted to determine the relative susceptibility to yield losses of four cultivars of processing tomato plants exposed to ozone (O3) and to determine if physiological characteristics of the cultivars could be used to predict cultivar responses to O3. Four field-grown tomato cultivars were exposed in open-top chambers to charcoal-filtered air (CF), non-filtered air (NF), and NF plus 1.5 times ambient O3 (NF150) from July to October in Riverside, CA. Results showed that ambient levels of O3 had relatively little effect on vegetative growth or yields of these tomato cultivars, but that 1.5 times ambient O3 concentrations reduced yields from 17% in cv. “UC204C” to 54% for cv. “Hybrid 31”. However, the cultivar-by-O3 interaction term in the ANOVA of yield data was not statiscally significant, indicating that in this experiment the cultivars responded relatively uniformly to O3. Rates of stomatal conductance were also relatively uniform among the cultivars, and conductance rates were not correlated with cultivar responses to O3. The hypothesis that differences in cultivar responses to O3 could be predicted by measurements of rates of maximum stomatal conductance was not confirmed by this study.

Physiological and growth responses of differentially irrigated cotton to ozone

This study was conducted to determine the physiological and growth responses of cotton (Gossypium hirsutum L.) to the interaction of ozonee (O3) and drought stress. Cotton (cv SJ-2) was grown in open-top chambers in the field at three levels of soil water and exposed to charcoal-filtered air (CF), nonfiltered air (NF), and NF x 1.25, and NF x 1.5 ambient O3 concentrations in Riverside, CA, from June to October 1986. Ozone reduced carbon fixation an average of 74.6% in optimally watered (OW) plots, 63.4% in suboptimal (SO) plots, but only 19.3% in severely water-stressed (SS) plots. Leaf and stem biomass in OW and SO plots showed similar linear reductions in mass response to increased O3 concentrations, but SS plots showed no response to O3 except at the highest O3 treatment (seasonal 12-h O3 mean of 0.111 ppm 218 microm(-3)). These results showed that moderately water-stressed cotton had similar physiological and growth responses to O3 as well-watered plants, but severely water-stressed cotton showed little response to O3 at ambient O3 concentrations.

Effects of SO2 on stomatal conductance and growth of Phaseolus vulgaris

Abstract Exposure of intact pinto beans Phaseolus vulgaris L. and those with cotyledons removed immediately after germination to 0·15, 0·25 and 0·50 ml litre −1 SO 2 at an identical dose (0·5 ml litre −1 h −1 day −1 ) for four weeks reduced leaf area, shoot and root dry weights and increased shoot/root ratios and specific leaf areas in all exposed plants. Bean plants with cotyledons removed were smaller than intact plants, but responses to SO 2 were similar in both groups. Increasing the concentration of SO 2 reduced growth to a greater degree than increasing the duration of exposure. Stomatal conductances decreased immediately after exposure as a function of increased concentration of SO 2 but conductances returned to control levels one day after termination of exposures. Reductions in stomatal conductance in response to SO 2 were proportional to reductions in plant growth. These results support the concept that SO 2 at dosages below levels at which foliar injury symptoms develop can decrease stomatal conductance, reduce plant growth and alter partitioning of dry matter into leaves, shoots and roots. These results do not support the contention that slower growing plants show greater growth responses to SO 2 than more rapidly developing plants.

Oxidant air pollution effects on plants of Joshua Tree National Monument.

Joshua Tree National Monument (JOTR) is located about 100 km east of the Los Angeles Basin, site of the heaviest concentration of photochemical oxidant (O(3)) air pollution in the US. This investigation was conducted to measure O(3) concentrations in JOTR and to determine the effects of O(3) on vegetation in the park. Potentially phytotoxic concentrations of O(3) were recorded in JOTR in 1984 and 1985, but peak concentration occurred at night, when most plant species would be less sensitive to O(3). No O(3) effects were observed on permanent vegetation observation plots in JOTR in 1984 or 1985. Controlled exposures of native summer annual and woody perennial species to O(3) showed that most did not develop visible O(3) injury symptoms except at concentrations higher than those expected in the park. However, Rhus trilobata Nutt. was injured at 0.10 ppm O(3), 4 h per day for 4 days. This species would be a useful bioindicator to assess the effects of O(3) on native desert plants.

Effects of ozone on yield of two field-grown barley cultivars

Abstract Barley Hordeum vulgare L. is grown in some regions of the USA with potentially phytotoxic concentrations of ozone (O 3 ), yet relatively little is known of the growth and yield responses of this crop species to O 3 . A two-year study was conducted in the Central Valley of California to determine yield responses of two cultivars of spring barley grown in open-top chambers to a gradient of O 3 concentrations. Ozone concentrations were maintained in chambers in proportion to ambient levels. Exposure levels ranged from charcoal-filtered air to twice ambient concentrations. Results indicated that neither Poco, grown in 1982, nor CM-72, used in 1983, was injured or reduced in growth by the relatively low ambient O 3 concentrations (0·03–0·05 μl litre −1 ) found in late winter or spring in the Central Valley. Twice ambient concentrations of O 3 also had no effect on the growth and yield of these cultivars. These results suggest that the threshold for an effect of O 3 on the yield of these cultivars of spring barley is above a seasonal 7 h (0900–1600) mean of 0·06 μl litre −1 .

Interactive effects of simulated acidic fog and ozone on field-grown alfalfa

Abstract Acid precipitation events, primarily in the form of fogs with pH as low as 2.0, have been reported from both urban and agricultural areas of California. If low pH acidic precipitation increased stomatal conductance, flux of gaseous air pollutants into mesophyll spaces could increase, thereby increasing susceptibility of plants to air pollution injury. The potential for this interaction is acute in California because of high ambient ozone (O3) levels present in areas frequently subjected to fogs. A field experiment was conducted to determine the interactive effects of simulated acidic fog and O3 on stomatal conductance, photosynthesis, foliar injury, and yield of an established stand of alfalfa (Medicago sativa L.). Plants were exposed to five levels of O3 for 12 hr daily for 4 weeks. Ozone was added in proportion to its concentrations in ambient air. Levels ranged from 1 4 of ambient to twice ambient concentrations. Simulated fog solutions of pH 2.0, 3.2, 4.4, and 5.6 acidified with 2:1 HNO3:H2SO4 were applied from 0300 to 0500 three times per week for 4 weeks. Treatments were replicated twice. Alfalfa was harvested when plants were at 1 10 bloom stage and crown sprouts exceeded 4 cm in length. Results indicated that both stomatal conductance and photosynthesis decreased with increasing acidity of fog. Foliar injury attributable to acid deposition was observed only in the pH 2.0 fog treatment. Alfalfa yield was significantly reduced by both acid fog and O3, but the interaction between the two was not statistically significant. The threshold for significant growth reduction in alfalfa exposed to simulated fog in open-top chambers was pH 2.0 and pH 3.2 for alfalfa in ambient-air plots.

Yield response of head lettuce (Lactuca sativa L.) to ozone

Abstract Head lettuce ( Lactuca sativa L. cv ‘Empire’) was grown in the field and exposed in open-top chambers to proportional increments of ozone (O 3 ) from full charcoal filtration (CF) to twice ambient O 3 concentrations (NF × 2.0). Severe foliar injury developed on young plants exposed to O 3 concentrations 1.7 and 2.0 times greater than ambient (seasonal 7 hr means of 0.104 and 0.128 ppm, respectively). These exposure levels also reduced total head weight 13 and 35%, respectively, compared with CF plants. Marketable-sized head weight was reduced 21 and 80%, respectively. Plants in O 3 -added chambers matured 2–3 weeks later than plants in low O 3 chambers. Regression analysis of yield data indicated that the threshold for significant yield reduction of head weight was > 0.083 ppm (seasonal 7-hr O 3 mean).