Cherry Belle Research Articles

Dose-response studies with ethylenediurea (EDU) and radish

There is some concern that the antiozonant ethylenediurea (EDU), used for crop loss assessment due to ambient ozone (O 3) may per se affect plant growth and yield. In view of this, and to provide knowledge for later field experiments, dose-response studies with EDU and O 3 were carried out in greenhouses in winter and spring 1989, using radish ( Raphanus sativus L.) cv. ‘Cherry Belle’ and ‘Red Prince’, grown in two different substrates. EDU was applied as a single or repeated soil drench in concentrations ranging from 300 to 800 mg litre −1 in the first, and from 100 to 400 mg litre −1 in the second trial. In the second experiment, plants were exposed to a chronic level of O 3, mimicking ambient patterns, or to filtered air after the EDU-treatment. When applied in concentrations above 300 mg litre −1, EDU reduced growth, thereby affecting the development of the thickened hypocotyl far more than the shoot growth that was partially stimulated by lower doses of EDU. Phytotoxic symptoms on the leaves, attributable to EDU, were observed at concentrations above 200 mg litre −1, but complete protection from visible O 3-injury was provided by a single application of EDU at a concentration as low as 100 mg litre −1. Significant interactions on growth characters measured between O 3-exposure and EDU application were observed only in one of the substrates. While these results demonstrate the need for careful dose-response studies prior to field assessments, they also provide evidence of a dosage that is effective in protecting radish from O 3 damage without interfering with plant growth itself.

Response of radish to multiple stresses

SUMMARYExperiments were conducted 10 determine what impact ozone (O3) and/or soil moisture deficit had on tile growth and development of radish plums. Plants of Raphanus sativus L. Cherry Belle and Raphanus sativus × raphanistrum (wild type) grown in modified open‐top chambers, were treated with O3 and/or subjected to reduced soil moisture throughout growth and development. Experiments were performed in the spring and autumn of 1989. Plants nr both genotypes exhibited a more adverse response to soil moisture deficit in the spring experiment and in O3, in the autumn experiment. The higher light intensity and temperature prevailing in the spring, in contrast to those during the autumn, were thought to favour a negative impact of reduced soil moisture. The spring conditions fostered high relative growth rate and more rapid water loss by the shoot on both a relative and absolute basis. These same conditions may have placed the plants in a physiological state which minimized toxicity by O3. Carbon partitioning in the spring favoured reproduction while the autumn carbon was preferentially partitioned to the hypocotyl and foliage for Cherry Belle and Wild Type, respectively. The importance of these partitioning differences between genotype was explored as it related to injurious and compensatory responses to the two Stresses. Since the plants were not equally sensitive to reduced soil moisture and O3, in the same experiments, interactions were frequently absent. When interactions occurred, O3 injury was reduced in plants also grown in soil with reduced moisture content.

The influence of CO2 and O3 , singly and in combination, on gas exchange, growth and nutrient status of radish (Raphanus sativus L.).

Five days after emergence radish (Raphanus sativus L. ev. Cherry Belle) plants were transferred to a phytotron at the GSF München, where they were exposed in four large controlled climate chambers to two atmospheric concentrations of CO2 , ('ambient', daily means of ∼ 385 μmol-1 ; elevated, daily means of ∼ 765 μmol mol-1 ) and two O3 regimes ('non-polluted' air, 24 h mean of 20 nmol mol-1 ; polluted air, 24 h mean of 73 nmol mol-1 ). Leaf gas-exchange measurements were made at intervals, and visible O3 damage, effects on growth, dry matter partitioning and mineral composition were assessed at a final whole-plant harvest after 27 d. In 'non-polluted air' CO2 enrichment resulted in a progressive stimulation in Asat , whilst there was a decline in g which decreased E (i.e. improved WUEi ). The extra carbon fixed in elevated CO2 stimulated growth of the root (+ hypocotyl) by 43 %, but there was no significant effect on shoot growth or leaf area. Moreover, a decline in SLA and LAR in CO2 -enriched plants suggested that less dry matter was invested in leaf area expansion. Tissue concentrations of N, S, P, Mg and Ca were lower (particularly in the root + hypocotyl) in elevated CO2 , indicating that total uptake of these nutrients was not affected by CO2 , and there was an increase in the C:N ratio in root (+ hypocotyl) tissue. In contrast, O3 depressed Asat , (∼ 26%) and induced slight stomatal closure, with the result that WUE, declined. All plants exposed to 'polluted' air developed typical visible symptoms of O3 injury, and effects on carbon assimilation were reflected in reduced growth, with shoot growth maintained at the expense of the root. In addition, O3 increased the P and K concentration in shoot and root (+ hypocotyl) tissue, indicating enhanced uptake of these nutrients from the growth medium. However, there was no affect of O3 on tissue concentrations of N, S, Mg and Ca. Interactions between the gases were complex, and often subtle. In general, elevated CO2 counteracted (at least in part) the detrimental effects of phytotoxic concentrations of O3 , whilst conversely, O3 reduced the impact of elevated CO2 . Moreover, there were indications that cumulative changes in source: sink relations in O3 -exposed plants may limit plant response to CO2 -enrichment to an even greater extent in the long-term. The future ecological significance of interactions between CO2 and O3 are discussed.

Effects of ambient rain chemistry on field-grown radish ? An exploratory approach by multiple linear regression

In a modeling approach multiple regression was used to describe plant growth of radish (Raphanus sativus L. cv. ‘Cherry Belle’) by a range of environmental variables including chemical characteristics of ambient rain. In a 2-yr field study, staggered radish crops were harvested in 2-d intervals. During the entire vegetative growth, the weights of the major organs (shoot, hypocotyl, root) were determined and mean relative growth rates (RGR) were calculated. Different climatic variables, which were modified by a range of time lag periods, were combined to describe total plant RGR and hypocotyl RGR for each of 2 or 3 developmental phases of the crop. In a second step, variables characterizing the ion concentration and deposition of ambient rain (mean pH 4.35 and 4.15 in 1989 and 1990, respectively) were introduced and tested for their significance of contribution to the models. Generally, the earlier development stages of radish were more responsive to changes in environmental variables and the growth models were improved significantly by introducing variables of rain chemistry during these early growth phases only. Hypocotyl growth was not more sensitive to the chemical composition of rain than was total plant growth. Disparities in frequency and amount of rain between the 2 yr may have caused differences in the relative contribution of rain chemistry variables towards the models. The limitations and advantages of this modeling approach are discussed in respect to the importance of different growth stages on the sensitivity to acid rain stress.

Timing of ozone stress and resulting status of ribulose bisphosphate carboxylase/oxygenase and associated net photosynthesis

summaryExperiments were conducted to determine how the timing of an exposure to ozone influenced the impact of the gas on ribulose‐ 1,5‐bisphosphate carboxylase/oxygenase (Rubisco) throughout the life span of a designated leaf. Saplings of Populus maximowizii×trichocarpa NE 388 received 5‐d exposures to O3 in growth chambers during and at the termination of presumed synthesis of Rubisco in a designated leaf. Ozone had no detectable impact on Rubisco activity or quantity when the exposure occurred during the time of increasing concentration of the protein in the leaf. When the concentration of Rubisco was near its peak, O3 induced a reduction in quantity and activity of Rubisco, but after cessation of the O3 stress, levels converged with those of the untreated tissue. When O3exposure occurred after full leaf expansion, minimal effects of the gas could be detected. When plants of hybrid popular or Raphanus sativus L. cv. Cherry Belle received chronic O3 treatment throughout the lifespan of the leaf, Rubisco activity and quantity declined more rapidly and never converged with values of untreated tissue.Studies of gas exchange revealed that changes in Rubisco were associated with a decline in net photosynthesis (A) and that these effects preceded the observed reduction in foliar conductance. CO2 response curves were measured periodically, and the initial slope (linear portion) of the curve, reflecting carboxylation capacity, declined more rapidly with leaf age in O3‐treated than in untreated poplars. There was no effect of O3 on stomatal limitation to CO2, assimilation except for a slight increase during the last 2 wk of the 9‐wk experiment. This supported the hypothesis that O3 effects on A were associated with CO2‐fixing capability of the leaf.

Effects and Interactions of Ozone and the Anti-ozonant EDU at Different Stages of Radish {Raphanus sativusL.) Development

The use of the anti-ozonant ethylenediurea (EDU) to assess crop losses due to atmospheric ozone (03), is controversial because of incomplete knowledge on the optimal dosage, the extent of protection provided and potential effects on plant performance of EDU per se. In a greenhouse experiment, radish (Raphanus sativus L.) cv. 'Cherry Belle' plants were treated with EDU as a soil drench (150 mg l-1, 60 ml plant-1) at three stages of development: early, maximum and late hypocotyl thickening. Two days later the plants were exposed to 03, mimicking an ambient pattern (70 ni l-1 03, 7 h d_1, 5 d, and up to 120 ni l-1 03 on 2 d), or remained in filtered air. Assessment of leaf injury showed complete protection from ozone-induced leaf damage at all stages of growth due to EDU. EDU did cause slight leaf margin necrosis and hyponastic leaf deformation irrespective of the atmospheric treatment, but biomass and relative growth rate (RGR) of the shoot and leaf number duration were not altered and leaf area duration was increased when compared to control plants. EDU did not affect dry weight accumulation nor RGR of the hypocotyl. Ozone-induced reductions in growth of below-ground organs (hypocotyl and root), which were most prominent in the intermediate and early stage of growth, were largely suppressed by the EDU-treatment. Decreases of hypocotyl biomass due to 03 were transient and significant increases in RGR of the hypocotyl during the post-exposure period indicated a substantial capability of compensation during the period of recovery.

Acclimation to ozone stress in radish: leaf demography and photosynthesis

summaryWhole plant acclimation to ozone exposure in growth‐chamber cultivated radish (Raphanus sativus L. cv. Cherry Belle) was investigated. The primary goal was to separate developmental from physiological ozone acclimation processes. Plants were grown for 37 days at two different lengths of ozone exposure and a control treatment. After germination, seedlings were transplanted into controlled growth chambers and exposed to daytime (10 h) ozone (0.12 μl 1−1) either on the next day (continuous ozone treatment) or three days later (intermediate treatment) and compared to a control (average ambient ozone concentration (0.01–0.02 μml 1−1). Plants grown in ozone after transplanting accumulated considerably less biomass than the controls, but had higher dry weights than the intermediate treatment, implying an acclimation response. Photosynthetic capacity and nitrogen content of leaves decreased at high levels of ozone exposure resulting in an accelerated leaf senescence. No distinct leaf‐level physiological acclimation to ozone exposure was seen based on gas exchange measurements. As an apparent compensatory response, plants exposed to ozone had higher leaf production rates than control plants, at the expense of root and hypocotyl growth. This developmental, whole‐plant response appeared to be the most effective acclimation response to ozone exposure seen in radish. However, it did not fully compensate for the damage caused by ozone, since plants still showed considerable reductions in growth.

Response of radish to multiple stresses: I. Physiological and growth responses to changes in ozone and nitrogen.

Experiments were conducted to determine the impact of nitrogen and ozone (O3 ) stress on the growth of domestic radish Raphanus sativus L. cv. Cherry Belle. Plants were grown in field chambers with sub-, optimal and supra-optimal levels of nitrogenous fertilizer. Chamber air was either charcoal-filtered, or supplemented with one of two levels of O3 . The highest O3 treatment resulted in significant reduction in weight of hypocotyls and roots while elevated nitrogen treatments resulted in increased weight of all plant parts. Ozone did not affect the weight of plant foliage at any nitrogen level. Plants grown with lower levels of nitrogen had less leaf biomass but the tissue accounted for a greater percentage total weight than did the foliage of higher nitrogen treatments. Relative growth rate of whole plants was not affected by O3 or nitrogen treatments reflecting compensation in response to both stresses. Ozone-induced depression in biomass was observed in O3 -treated plants grown with higher nitrogen supply but not in those grown with limiting nitrogen. This observation could reflect compensation at the lower levels of nitrogen supply or inability to detect changes in biomass due to reduced weights of plants grown at the lowest nitrogen supply. The dry weight ratio of sink organs (hypocotyl plus root)/shoot was significantly correlated with the total non-structural carbohydrate (TNC) content of these organs, regardless of treatment. Initially, O3 induced a significant decrease and nitrogen an increase in percent TNC of sink organs. At later sampling times, plants adjusted to stress as effects on percent TNC were no longer evident.

Development of lines of radish differing in resistance to O3 and SO2

SUMMARYThe potential for developing intraspecific lines of radish (Raphanus sativus L. cv, Cherry Belle) based on their relative resistance to either O3 or SO2 was examined using growth‐analysis techniques. Plants were exposed to either 0–10μ 1−1 O3 or 0.50 μ 1 −1 SO2 for 4 h day−1, 3 days week−1, for 3 weeks. Resistant and sensitive individuals were then selected and divided into four groups: O3 resistant (O3R), O3 sensitive (O3S), SO2 resistant (SO2R), and SO2 sensitive (SO2S) Cross‐pollinations were made among plants within the selected groups and seed collected. F1 populations were raised from the resulting seed and exposed to the same exposure regime. Net photosynthesis and stomatal conductance were measured during the final two fumigations, and plants were harvested immediately following the final exposure, divided into component parts, dried and weighed.O3 and SO2 generally caused biomass reductions in all the F1 groups. O3 reduced below ground growth more than SO2 leading to greater reductions in root/shoot ratios. O3R plants were resistant to both pollutants, showing little biomass reduction particularly from O3. Root/shoot ratios of these plants were altered less by pollutant exposure than non‐selected radishes. Shoot growth of SO2R plants was greater in O3 or SO2 than non‐selected plants, but below ground growth was similar. Selection for plants sensitive to either pollutant was not apparent from growth analysis, as growth of the sensitive plants was generally the same as that of non‐selected plants. Gas exchange results indicated greater stomatal conductance in O3S plants in filtered air than either non‐selected or O3R plants, while O3S plants had lower conductance rates in the O3 treatment.

Growth and mineral composition of radish under different nitrification inhibitors and nitrogen sources

Abstract Captan [N‐(trichloromethylthio)‐4‐cyclo‐hexene‐l, 2‐dicarboximide] and benomy1[methyl 1‐(butylcarbamoyl)‐2‐benzimidazolecarbamate] were evaluated as nitrification inhibitors and compared with nitrapyrin [2‐chloro‐6‐(trichloromethyl)pyridine]. Nitrapyrin, captan, and benorayl were applied at 0, 20, 40, and 60 mg/kg with three nitrogen sources, KNO3, (NH4)2SO4, and urea, at 300 mg N/kg to ‘Cherry Belle’ radish (Raphanus sativusL). Nitrapyrin and captan inhibited nitrification effectively, but benomyl was not an effective inhibitor. Growth of radish roots and shoots was restricted with application of nitrapyrin and captan combined with (NH4)2SO4or urea relative to the comparable KNO3treatments. The concentrations of Ca, Mg, and NO3‐N in plants, especially in shoots, fell, and the percentage of ? was increased with the addition of nitrapyrin and captan. Benomyl did not affect plant growth or composition

Critical calcium concentrations in radish grown under various regimes of nitrogen nutrition

Abstract Ammonium nutrition of radish plants (Raphanus sativus L.) suppresses their accumulation of Ca. The objective of this study was to determine the critical Ca concentration of radish in order to assess if NH4 + nutrition induces Ca deficiency in this crop. Cultivar Cherry Belle was grown in sand culture in a greenhouse. Nitrogen was provided as nitrate or ammonium salts, and Ca was varied from 1 to 200 mg/liter in solution. With N03’ nutrition, plant growth increased curvilinearly with increased Ca in solution. Calcium accumulation in shoots was a good index of relative root (edible radish) growth. The critical Ca concentration in shoots for optimum root growth was 2% of the dry matter. With NH4+ nutrition, plant growth declined linearly with increased Ca in solution and with Ca accumulation in the shoots. A critical Ca concentration could not be determined for plants grown with NH4 + nutrition. The antagonism between Ca and NH4 + nutrition could not be explained by deficiencies or toxicities of other elements.

The relationship between changes in photosynthesis and growth for radish plants fumigated with SO2 and O3

SUMMARYThe effects of possible ambient concentrations of SO2 and O3 on biomass production and gas exchange of radish (Raphanus sativus L, cv. Cherry Belle) are examined, the relationship between photosynthesis and growth is defined and the mechanisms behind pollutant induced changes in growth are elucidated.Ozone was shown to be considerably more phytotoxic than SO2. Fumigation at a concentration as low as 5 μmol O3 m−3 (0.12μl 1−1) produced ‘visible’ injury. No ‘visible’ injury symptoms were apparent with plants fumigated with SO2. The effect of fumigation with Oa at concentrations greater than 2.5 μmol m−3 (0.06 μl 1−1) was to reduce biomass production and alter carbon partitioning. This was not so for SO2, fumigated plants. Ozone‐fumigated plants showed a significant reduction in their photosynthetic efficiency (NAR) and despite an increase in LAR, RGR was still depressed below control values.The relationship between photosynthesis and biomass production for fumigated plants was examined and whole plant carbon acquisition was calculated from gas‐exchange measurements. On comparing calculated carbohydrate production with measured biomass accumulation, it was dear that changes in A were closely related to changes in growth.Light‐ and CO2‐response curves were used to determine maximum light‐saturated photosynthesis (Amax), incident quantum yield (QY) and carboxylation efficiency (d.A/de1), RuBP‐regeneration capacity (Jmax) respectively. The presence of SO2 over a concentration of 2.5–8.3 μmol m−3 (0.12–0.20 μl −1) enhanced Amax. QY and Jmax, However, dA/dc1, was reduced at all concentrations. This reduction was offset by an increase in Jmax. At the smallest O3 concentration (2.5 μmol m−3) Amax was stimulated and at the higher concentration severely reduced. Q Y was not negatively influenced by the presence of O3, but d.A/dc1 and Jmax were reduced, particularly as the dose increased.

Sensitivity of Plants to Acidic Fog

AbstractSeveral crop species were exposed to simulated acidic fog from pH 1.6 to 3.2 or to 5.6 in greenhouse experiments. Foliar injury and growth of radish (Raphanus sativus L. cv. Cherry Belle), tomato (Lycopersicon esculentum Mill. cv. Tiny Tim), onion (Allium cepa L. cv. Southport White Globe), spinach (Spinacia oleracea L. cv. Bloomsdale Long Standing), bean (Phaseolus vulgaris L. cvs. Pinto and Improved Kentucky Wonder), alfalfa (Medicago sativa L. cvs. Mesa Sirsa and Moapa 69), sweet orange (Citrus sinensis L. cv. Valencia), and trifoliate orange (Poncirus trifoliate L.) were determined after exposure to simulated fog at acidites down to pH 1.6. Potted plants were exposed for 2 h after sunset on 2 consecutive days every week for 4 (radish) or 12 (others) weeks. Acidic fog at ambient pH levels injured plants, but large amounts of acidic input were required for injury to occur. Although crop species varied in magnitude of response to acidic fog, in general, pH 3 or below was required to induce foliar injury and pH 2 or below was required to induce foliar injury and pH 2 or below to reduce growth. Radish, spinach, alfalfa, and Valencia orange were sensitive to foliar necrosis from acidic fog, while onion was tolerant. Acidic fog reduced yields of dry bean and spinach, reduced root weight of tomato, and delayed maturity of bean and alfalfa.

Accumulation of di‐n‐butylphthalate in plants and its effect on pigment and protein content

Seedlings of radish (Raphanus salivas L. cv. Cherry Belle) and wheat (Triticum aestivum L. cv. Starke II, Weibull) placed in air containing vapour of di‐n‐butyl‐phthalate accumulate phthalate to a concentration that is 106 times that of the surrounding air within 3 days. Particularly high accumulation is found in the cuticular and wax layers. Plants earlier found not to respond to di‐n‐butylphthalate (wheat) show toxic symptoms (carotenoid and chlorophyll deficiency in strong light, conco‐mittant with chloroplast destruction and swollen mitochondria) when the phthalate concentration is further increased by addition to the nutrient medium. Phthalate‐affected, white leaves lack the protein moieties normally belonging to the light harvesting complex.

Accumulation of Selenium in Crops Grown on Sludge‐treated Soil

AbstractUptake by barley (Hordeum vulgare L. var. Briggs), Swiss chard (Beta vulgaris L. var. Fordhook), and radish (Raphanus sativas L. var. Cherry Belle) of Se from composted Los Angeles County sewage sludge applied to land was studied in a long‐term field study. Sludge was applied at 0, 22.5, 45, 90, and 180 Mg/ha per year for 8 to 10 yr and the data reported here are for the last year of the study. Total surface (0–15 cm) soil Se increased with the highest rate of sludge addition from <0.1 mg/kg in the control soil to 1.2 mg/kg. Only 13 to 25% of the sludge‐applied Se could be accounted for in the 0‐ to 15‐cm depth of incorporation and there was no measurable Se (<0.1 mg/kg) in the subsoil to 150 cm. There was little or no measurable uptake of Se by barley leaf and grain at the level of detection (0.05 mg/kg) of this study, and there were also no significant increases in chard or radish Se concentrations with sludge addition. Selenium concentrations in chard (0.05–0.11 mg/kg) were severalfold lower than those in radish (0.17–0.26 mg/kg).

Long‐term Sludge Applications on Cadmium and Zinc Accumulation in Swiss Chard and Radish

AbstractSwiss chard (Beta vulgare var. Fordhook) and radish (Raphanus sativus var. Cherry Belle) were grown twice annually (spring and fall) on a Ramona sandy loam (fine‐loamy, mixed thermic, Typic Haploxeralfs) soil treated with 0, 22.5, 45, 90, and 180 Mg ha−1 yr−1 of composted sludges from Los Angeles. The soil received two sludge inputs of equal amounts each year and crops were planted shortly after each sludge incorporation. Cadmium and Zn accumulation of the plant tissue from 1976 to 1985 was examined. Results from the analysis of variance indicated that effects due to sludge application rates, seasons plants were grown, number of years of sludge application, and their interactions were all significant. If the data sets were partitioned according to sludge application rates and seasons, metal concentrations of the plant tissue may be expressed as a nonlinear regression model, y = a + b (1 − e−cx), where y is the metal concentration of the plant tissue, x is the cumulative sludge loading, and a, b, and c are constants. All but two nonlinear regressions were significant at p <0.05 with R2 from 0.38 to 0.95. The deviation of the observed values from the predictions of the regression model indicated that other factors might have also affected the metal uptake by plants. Stepwise multiple regression analysis of the partitioned data sets indicated that soil pH, soil salinity, soil temperature, and length of growing season influenced the metal accumulation in plant tissue.

Boron nutrition and mobility, and its relation to the elemental composition of greenhouse grown root crops. II radish

Abstract The elemental distribution between the leaves and roots of mature radish (Raphanus sativus cv Cherry Belle) plants grown in the greenhouse with various concentrations of nutrient solution B or Ca was determined to assess the role of phloem in the provision of nutrients to the root, and the retranslocation of B under deficient conditions. The relative composition and accumulation of elements in different parts, and the ratio of their concentrations in leaves:roots were used as a measure of their uptake, relative mobility and retranslocation. The data indicate that B, but not Ca is retranslocated in the phloem to the roots when that particular element was in short supply in the nutrient solution. B deficiency induced brown heart disorder in radish roots but the severity was dependent on the degree of deficiency below 28 μg g‐l DM in the root. These symptoms were alleviated when the root B concentrations were enhanced by foliar applications of B. It is concluded that radish responded to B deficiency in a fashion similar to that reported previously for rutabaga and that it might serve as a time‐saving model system for examining the mechanisms responsible for brown heart in rutabaga.

Growth and Mineral Composition of Radish in Response to Nitrification Inhibitors

Abstract Nitrapyrin, etridiazol, fenaminosulf, sodium azide, and a formulated product of aromatic substances and alkenes were evaluated as nitrification inhibitors under greenhouse conditions for radish (Raphanus sativus L. ‘Cherry Belle’) fertilized with sewage sludge. Nitrapyrin and etridiazol inhibited nitrification, but their use restricted plant growth and lowered the Ca and Mg concentrations of the plants. Nitrification was inhibited slightly by fenaminosulf, which had little effect on plant growth and composition. Sodium azide and the formulated product were not effective as nitrification inhibitors. The azide was phytotoxic, but the formulated product had no toxic effects on growth. The toxic effects of chemicals with efficacy as nitrification inhibitors were due largely to the accumulation of NH4-N in the medium. Chemical names used: 2-chloro-6-(trichloromethyI)pyridine (nitrapyrin); 5-ethoxy-3-trichloromethyl-1,2,4-thiadiazole (etridiazol); and sodium p-(dimethylamino)benzenediazosulfonate (fenaminosulf).

Ethylene production by potato, radish and soybean leaf tissue treated with simulated acid rain

Solanum tuberosum cv. ‘Norland’, Raphanus sativus cv. ‘Cherry Belle’ and Glycine max cv. ‘Amsoy 71’ were treated with simulated acid rain solutions of pH 2.8, 3.8, 4.6 and 5.6. Two treatment durations were used: 1-hr/day for a single day, or 1-hr/day for three consecutive days. There was also a ‘no rain’ treatment. Petioles of excised leaves were immersed in 2 ml of 0.5 mM 1-aminocyclopropane-1-carboxylic acid (ACC) and 200 mM NaHCO 3 in the base of a 50 ml flask. Flasks were sealed and incubated for 24 hr in the dark. Air was sampled and ethylene concentrations quantified on a nl/g dry weight basis using a gas chromatograph fitted with an activated alumina column and a flame ionization detector. Potato leaves exhibited 1% injury after 1-hr or three 1-hr treatments. After three 1-hr treatments, radish leaves sampled exhibited 10–25% injury. No injury was observed on soybean, potato, or radish leaves at any other treatment level. No species exhibited increased ethylene production in response to 1-hr rain treatments. After multiple rain treatments, plants treated with pH 2.8 rain generally exhibited increased ethylene production; however, no direct relationship between ethylene production and treatment acidity was observed. Regardless of treatment pH or duration, radish foliage produced more ethylene than did potato or soybean foliage. Although differential ethylene production among species was observed, production in response to acid rain did not appear to be a sensitive indicator of plant stress.

Comparative Toxicology of Laboratory Organisms for Assessing Hazardous Waste Sites

AbstractMulti‐media/multi‐trophic level bioassays have been proposed to determine the extent and severity of environmental contamination at hazardous waste sites. Comparative toxicological profiles for algae (Selenastrum capricornutum), daphnia (Daphnia magna), earthworms (Eisenia foetida), microbes (Photobacterium fisherii, mixed sewage microorganisms) and plants; wheat “Stephens,” (Triticum aestivum), lettuce, butter crunch, (Lactuca sativa L.), radish, “Cherry Belle,” (Raphanus sativa L.), red clover, “Kenland,” (Trifolium pratense L.) and cucumber, “Spartan Valor,” (Cucumis sativa L.) are presented for selected heavy metals, herbicides and insecticides. Specific chemical EC50 values are presented for each test organism. Differences in standard deviations were compared between each individual test organism, as well as for the chemical subgroup assayed. Algae and daphnia are the most sensitive test organisms to heavy metals and insecticides followed in order of decreasing sensitivity by Microtox (Photobacterium fisherii), DO depletion rate, seed germination and earthworms. Higher plants were most sensitive to 2,4‐D, (2,4‐Dichlorophenoxy acetic acid) followed by algae, Microtox, daphnia and earthworms. Differences in toxicity of 2,4‐D chemical formulations and commercial sources of insecticides were observed with algae and daphnia tests.