@article{blum_2022, title={The challenges of using treatment solution properties to determine concentrations for the inhibition of seedling processes by monoprotic phenolic acids}, volume={12}, ISSN={["1573-5036"]}, DOI={10.1007/s11104-022-05837-z}, journal={PLANT AND SOIL}, author={Blum, Udo}, year={2022}, month={Dec} }
 @article{blum_2021, title={Pioneers of Allelopathy: XVII. Udo Blum}, volume={52}, ISSN={["0973-5046"]}, DOI={10.26651/allelo.j/2021-52-2-1313}, abstractNote={Udo Blum had a teaching and research career of 34 years. His primary role was teaching, advising, and mentoring undergraduate and graduate students. He authored or co-authored research publications on plant-plant allelopathic interactions, air pollution biology, and salt marsh biology. He retired in 2002 and has subsequently written a three-volume retrospective analysis of his research on plant-plant allelopathic interactions involving phenolic acids. His primary research goals were to understand: (i) how cinnamic and benzoic acids released from plants into the soil affect sensitive seedlings and soil and rhizosphere microorganisms, (ii) how phenolic acids are distributed and partitioned in seedling-microbe-soil-sand systems and (iii) how their effects on sensitive seedlings are modified by abiotic soil factors (soil pH, soil moisture, soil nutrients, presence of other organic compounds) and soil processes (microbial utilization and soil sorption) in laboratory and field model systems. In 1999 he received the Molisch Award from the International Allelopathic Society for his research contributions to our understanding of Plant-plant allelopathic interactions.}, number={2}, journal={ALLELOPATHY JOURNAL}, author={Blum, Udo}, year={2021}, month={Mar}, pages={143–162} }
 @book{blum_2014, title={Plant-plant allelopathic interactions II: Laboratory bioassays for water-soluble compounds with an emphasis on phenolic acids}, publisher={New York: Springer Verlag}, author={Blum, U.}, year={2014} }
 @article{blum_gerig_2006, title={Interrelationships between p-coumaric acid, evapotranspiration, soil water content, and leaf expansion}, volume={32}, ISSN={["1573-1561"]}, DOI={10.1007/s10886-006-9111-2}, abstractNote={Increasing concentrations of p-coumaric acid applied to (cucumber seedling)-[Cecil A( p ) soil-sand mixture (or soil)] systems inhibited evapotranspiration (primarily transpiration) and leaf area expansion of cucumber seedlings and increased soil moisture. Higher soil moisture resulting from the inhibition of evapotranspiration lowered soil solution concentrations of p-coumaric acid by 14-40% but did not significantly influence the inhibitory effects of p-coumaric acid on seedlings. Inhibition of evapotranspiration and total leaf area and increases in lowest daily soil water were observed 1-3 d after the first p-coumaric acid treatment, whereas inhibition of absolute and relative rates of leaf expansion was observed within a 24-hr period. Development of the maximum effects of p-coumaric acid required several additional days. Recovery from effects, i.e., return to control levels, after p-coumaric acid depletion from soil solution was a gradual process requiring days for evapotranspiration, lowest daily soil water, and total leaf area, but was slightly faster for leaf area expansion. It appears, at least for short-term studies, that the initial input or treatment concentrations of p-coumaric acid represented a reasonable estimate of dose despite the dynamic nature of soil solution concentrations, and that the lowering of available p-coumaric acid concentrations, associated with the elevation of soil moisture, did not result in a concurrent detectable seedling response. However, increased soil moisture associated with p-coumaric acid treatments of sensitive species suggests a means by which the magnitude of some allelopathic interactions may be modified and resource competition and allelopathy could interact.}, number={8}, journal={JOURNAL OF CHEMICAL ECOLOGY}, author={Blum, Udo and Gerig, Thomas M.}, year={2006}, month={Aug}, pages={1817–1834} }
 @article{blum_gerig_2005, title={Relationships between phenolic acid concentrations, transpiration, water utilization, leaf area expansion, and uptake of phenolic acids: Nutrient culture studies}, volume={31}, ISSN={["0098-0331"]}, DOI={10.1007/s10886-005-5934-5}, abstractNote={Phenolic acid treatments of cucumber seedlings (Cucumis sativus cv "Early Green Cluster") inhibited transpiration, water utilization, leaf area, and absolute and relative rates of leaf expansion. The cinnamic acids, ferulic and p-coumaric acids, were two to five times more inhibitory than the benzoic acids, p-hydroxybenzoic acid and vanillic acid. When phenolic acid concentrations were maintained at inhibitory concentrations through multiple successive treatments, percent inhibition of water utilization remained relatively constant for a given concentration and phenolic acid, percent inhibition of leaf area initially increased and then leveled off to a constant percent, and percent inhibition of transpiration and rates of leaf area expansion declined over time. Subsequently, p-coumaric acid was chosen as the model compound for further study. When p-coumaric acid was inhibitory, percent inhibition of transpiration, water utilization, and rates of leaf area expansion of actively growing leaves rapidly declined (i.e., was lost) as p-coumaric acid concentrations surrounding roots decreased. Absolute and relative rates of leaf expansion, for example, declined approximately 12 and 14%, respectively, for every 0.1 mM decline in p-coumaric acid concentration. Uptake of p-coumaric acid by cucumber seedling roots was continuous over the 24- or 36-hr periods monitored, but was not consistently related to the initial p-coumaric acid treatment concentrations. However, declining p-coumaric acid concentrations monitored at 6- or 12-hr intervals over the 24- or 36-hr periods continued to be highly correlated to the initial p-coumaric acid treatment concentrations. A 25% depletion by 1 3-d-old cucumber seedlings took 8.5, 12, 19.5, 25, and 29.5 hr for 0.125-, 0.25-, 0.5-, 0.75-, and 1-mM treatments, respectively. Uptake during periods when phenolic acid concentrations and root uptake (depletion from solution) were related appeared to represent periods dominated by apoplastic movement into the intercellular spaces of roots. Uptake during periods without this relationship likely represented periods dominated by symplastic movement. The ability of cucumber seedlings to modify active phenolic acid concentrations surrounding their roots suggests that cucumber seedling can directly influence the magnitude of primary and secondary effects of phenolic acids through feedback regulation.}, number={8}, journal={JOURNAL OF CHEMICAL ECOLOGY}, author={Blum, U and Gerig, TM}, year={2005}, month={Aug}, pages={1907–1932} }
 @article{wright_warren_blazich_blum_2004, title={Root and shoot growth periodicity of Kalmia latifolia 'Sarah' and Ilex crenata 'Compacta'}, volume={39}, number={2}, journal={HortScience}, author={Wright, A. N. and Warren, S. L. and Blazich, F. A. and Blum, U.}, year={2004}, pages={243–247} }
 @article{blum_king_brownie_2002, title={Effects of wheat residues on dicotyledonous weed emergence in a simulated no-till system}, volume={9}, number={2}, journal={Allelopathy Journal}, author={Blum, U. and King, L. D. and Brownie, C.}, year={2002}, pages={159–176} }
 @article{staman_blum_louws_robertson_2001, title={Can simultaneous inhibition of seedling growth and stimulation of rhizosphere bacterial populations provide evidence for phytotoxin transfer from plant residues in the bulk soil to the rhizosphere of sensitive species?}, volume={27}, ISSN={["1573-1561"]}, DOI={10.1023/A:1010362221390}, abstractNote={In order to demonstrate that allelopathic interactions are occurring, one must, among other things, demonstrate that putative phytotoxins move from plant residues on or in the soil, the source, through the bulk soil to the root surface, a sink, by way of the rhizosphere. We hypothesized that the incorporation of phytotoxic plant residues into the soil would result in a simultaneous inhibition of seedling growth and a stimulation of the rhizosphere bacterial community that could utilize the putative phytotoxins as a sole carbon source. If true and consistently expressed, such as relationship would provide a means of establishing the transfer of phytotoxins from residue in the soil to the rhizosphere of a sensitive species under field conditions. Presently, direct evidence for such transfer is lacking. To test this hypothesis, cucumber seedlings were grown in soil containing various concentrations of wheat or sunflower tissue. Both tissue types contain phenolic acids, which have been implicated as allelopathic phytotoxins. The level of phytotoxicity of the plant tissues was determined by the inhibition of pigweed seedling emergence and cucumber seedling leaf area expansion. The stimulation of cucumber seedling rhizosphere bacterial communities was determined by the plate dilution frequency technique using a medium containing phenolic acids as the sole carbon source. When sunflower tissue was incorporated into autoclaved (to reduce the initial microbial populations) soil, a simultaneous inhibition of cucumber seedling growth and stimulation of the community of phenolic acid utilizing rhizosphere bacteria occurred. Thus, it was possible to observe simultaneous inhibition of cucumber seedlings and stimulation of phenolic acid utilizing rhizosphere bacteria, and therefore provide indirect evidence of phenolic acid transfer from plant residues in the soil to the root surface. However, the simultaneous responses were not sufficiently consistent to be used as a field screening tool but were dependent upon the levels of phenolic acids and the bulk soil and rhizosphere microbial populations present in the soil. It is possible that this screening procedure may be useful for phytotoxins that are more unique than phenolic acids.}, number={4}, journal={JOURNAL OF CHEMICAL ECOLOGY}, author={Staman, K and Blum, U and Louws, F and Robertson, D}, year={2001}, month={Apr}, pages={807–829} }
 @article{blum_staman_flint_shafer_2000, title={Induction and/or selection of phenolic acid-utilizing bulk-soil and rhizosphere bacteria and their influence on phenolic acid phytotoxicity}, volume={26}, ISSN={["0098-0331"]}, DOI={10.1023/A:1005560214222}, number={9}, journal={JOURNAL OF CHEMICAL ECOLOGY}, author={Blum, U and Staman, KL and Flint, LJ and Shafer, SR}, year={2000}, month={Sep}, pages={2059–2078} }
 @inbook{blum_1999, title={Designing laboratory plant debris-soil bioassays: Some reflections}, booktitle={Principles and practices in plant ecology: Allelochemical interactions}, publisher={Boca Raton, Fla.:  CRC Press}, author={Blum, U.}, editor={Inderjit, K. M. M. Dakshini and Foy, C.Editors}, year={1999}, pages={17–23} }
 @article{lehman_blum_1999, title={Evaluation of ferulic acid uptake as a measurement of allelochemical dose: Effective concentration}, volume={25}, number={11}, journal={Journal of Chemical Ecology}, author={Lehman, M. E. and Blum, U.}, year={1999}, pages={2589–2600} }
 @article{blum_shafer_lehman_1999, title={Evidence for inhibitory allelopathic interactions involving phenolic acids in field soils: Concepts vs. an experimental model}, volume={18}, DOI={10.1080/07352689991309441}, abstractNote={The accepted criteria for identifying allelopathic interactions in the field that have been proposed in the literature offer heuristic function, but to date have failed as a framework for research and diagnostics. If the present criteria are to be modified to make them useful empirically, their shortcomings must be identified. For this review, data from the literature and from defined model systems consisting of plants, soil, and/or microbes are used to evaluate the applicability of the accepted criteria to defined systems in which plants are responding to known allelochemicals. Based on this evaluation, modified criteria are proposed. In many respects, however, the modified criteria are as difficult to satisfy in the field as those proposed previously. The new criteria have value as a research framework because they clearly suggest that a shift in research focus to the soil environment, specifically the barrier of the rhizosphere through which allelochemicals must pass, is essential if the role of allelopathic interactions in the field is to be established.}, number={5}, journal={Critical Reviews in Plant Sciences}, author={Blum, Udo and Shafer, S. R. and Lehman, M. E.}, year={1999}, pages={673–693} }
 @article{lehman_blum_1999, title={Influence of pretreatment stresses on inhibitory effects of ferulic acid, an allelopathic phenolic acid}, volume={25}, ISSN={["1573-1561"]}, DOI={10.1023/A:1020828630638}, number={7}, journal={JOURNAL OF CHEMICAL ECOLOGY}, author={Lehman, ME and Blum, U}, year={1999}, month={Jul}, pages={1517–1529} }
 @inbook{blum_austin_shafer_1999, title={The fates and effects of phenolic acids in a plant-microbe-soil model system}, ISBN={8477865051}, booktitle={Recent advances in allelopathy:  I. A. science for the future}, publisher={Cadiz, Spain: Servicio de Publicaciones, Universidad de Cadiz}, author={Blum, U. and Austin, M. F. and Shafer, S. R.}, editor={F. A. Macias, J. G. C. Galindo and Molinillo, J. M. G. and Cutler, H.Editors}, year={1999}, pages={159–166} }
 @article{shafer_blum_horton_hesterberg_1998, title={Biomass of tomato seedlings exposed to an allelopathic phenolic acid and enriched atmospheric carbon dioxide}, volume={106}, ISSN={["0049-6979"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0032145076&partnerID=MN8TOARS}, DOI={10.1023/A:1004944731826}, number={1-2}, journal={WATER AIR AND SOIL POLLUTION}, author={Shafer, SR and Blum, U and Horton, SJ and Hesterberg, DL}, year={1998}, month={Aug}, pages={123–136} }
 @article{blum_1998, title={Effects of microbial utilization of phenolic acids and their phenolic acid breakdown products on allelopathic interactions}, volume={24}, ISSN={["1573-1561"]}, DOI={10.1023/A:1022394203540}, number={4}, journal={JOURNAL OF CHEMICAL ECOLOGY}, author={Blum, U}, year={1998}, month={Apr}, pages={685–708} }
 @article{blum_1997, title={Benefits of citrate over EDTA for extracting phenolic acids from soils and plant debris}, volume={23}, ISSN={["0098-0331"]}, DOI={10.1023/B:JOEC.0000006364.17425.75}, number={2}, journal={JOURNAL OF CHEMICAL ECOLOGY}, author={Blum, U}, year={1997}, month={Feb}, pages={347–362} }
 @article{lehman_blum_1997, title={Cover crop debris effects on weed emergence as modified by environmental factors}, volume={4}, number={1997}, journal={Allelopathy Journal}, author={Lehman, M. E. and Blum, U.}, year={1997}, pages={69–88} }
 @article{blum_king_gerig_lehman_worsham_1997, title={Effects of clover and small grain cover crops and tillage techniques on seedling emergence of dicotyledonous weed species}, volume={12}, DOI={10.1017/s0889189300007487}, abstractNote={Abstract}, number={4}, journal={American Journal of Alternative Agriculture}, author={Blum, Udo and King, L. D. and Gerig, T. M. and Lehman, M. E. and Worsham, A. D.}, year={1997}, pages={146–161} }
 @article{blum_1996, title={Allelopathic interactions involving phenolic acids}, volume={28}, number={3}, journal={Journal of Nematology}, author={Blum, U.}, year={1996}, pages={259} }
 @article{blum_1995, title={The value of model plant-microbe-soil systems for understanding processes associated with allelopathic interaction. One example}, ISBN={0841230617}, DOI={10.1021/bk-1995-0582.ch009}, abstractNote={ADVERTISEMENT RETURN TO BOOKPREVChapterNEXTThe Value of Model Plant—Microbe—Soil Systems for Understanding Processes Associated with Allelopathic InteractionOne ExampleUdo BlumUdo BlumDepartment of Botany, North Carolina State University, Raleigh, NC 27695-7612More by Udo BlumDOI: 10.1021/bk-1995-0582.ch009Publication Date (Print):December 9, 1994Publication History Published online23 July 2009Published inprint 9 December 1994Request reuse permissions Copyright © 1995 American Chemical SocietyAllelopathyChapter 9pp 127-131ACS Symposium SeriesVol. 582ISBN13: 9780841230613eISBN: 9780841215061 Chapter Views 44 Citations - LEARN ABOUT THESE METRICS Chapter Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days. Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options SUBJECTS:Organic acids,Plants,Soils Get e-Alerts}, journal={Allelopathy : organisms, processes, and applications}, publisher={Washington, D.C. : American Chemical Society}, author={Blum, Udo}, editor={Inderjit, Dakshini K. M. M. and Einhellig, F. A.Editors}, year={1995}, pages={127} }
 @article{blum_gerig_worsham_king_1993, title={MODIFICATION OF ALLELOPATHIC EFFECTS OF P-COUMARIC ACID ON MORNING-GLORY SEEDLING BIOMASS BY GLUCOSE, METHIONINE, AND NITRATE}, volume={19}, ISSN={["1573-1561"]}, DOI={10.1007/BF00980584}, abstractNote={Studies of allelopathy have emphasized primarily the identification and quantification of phytotoxins in soils, with only limited attention directed toward how organic (carbon) and inorganic constituents (nutrients) in the soil may modify the action of such phytotoxins. In the present study, increasing carbon (C) levels (up to 108μg C/g soil) supplied as glucose, phenylalanine, orp-hydroxybenzoic acid did not alter morning-glory biomass, but similar C levels supplied as leucine, methionine, orp-coumaric acid were inversely related to morning-glory biomass. Similar joint action and multiplicative analyses were used to describe morning-glory biomass response to various C sources and to generate dose isolines for combinations ofp-coumaric acid and methionine at two NO3-N levels and for combinations ofp-coumaric acid and glucose at one NO3-N level. Methionine, glucose, and NO3-N treatments influenced the inhibitory action ofp-coumaric acid on biomass production of morning-glory seedlings. For example, results from the multiplicative analysis indicated that a 10% inhibition of morning-glory biomass required 7.5μgp-coumaric acid/g soil, while the presence of 3.68μg methionine/g soil thep-coumaric acid concentration required for 10% inhibition was only 3.75μg/ g soil. Similar response trends were obtained forp-coumaric acid and glucose. The higher NO3-N (14 vs. 3.5μg/g) treatments lowered the methionine and increased thep-coumaric acid concentrations required for 10% inhibition of morning-glory biomass. These results suggested that allelopathic interactions in soil environments can be a function of interacting neutral substances (e.g., glucose), promoters (e.g., NO3-N), and/or inhibitors (e.g., methionine andp-coumaric acid) of plant growth.}, number={12}, journal={JOURNAL OF CHEMICAL ECOLOGY}, author={BLUM, U and GERIG, TM and WORSHAM, AD and KING, LD}, year={1993}, month={Dec}, pages={2791–2811} }
 @article{blum_gerig_worsham_holappa_king_1992, title={ALLELOPATHIC ACTIVITY IN WHEAT-CONVENTIONAL AND WHEAT-NO-TILL SOILS - DEVELOPMENT OF SOIL EXTRACT BIOASSAYS}, volume={18}, ISSN={["1573-1561"]}, DOI={10.1007/BF00984946}, abstractNote={The primary objective of this research was to determine if soil extracts could be used directly in bioassays for the detection of allelopathic activity. Here we describe: (1) a way to estimate levels of allelopathic compounds in soil; (2) how pH, solute potential, and/or ion content of extracts may modify the action of allelopathic compounds on germination and radicle and hypocotyl length of crimson clover (Trifolium incarnatum L.) and ivyleaved morning glory (Ipomoea hederacea L. Jacquin.); and (3) how biological activity of soil extracts may be determined. A water-autoclave extraction procedure was chosen over the immediate-water and 5-hr EDTA extraction procedures, because the autoclave procedure was effective in extracting solution and reversibly bound ferulic acid as well as phenolic acids from wheat debris. The resulting soil extracts were used directly in germination bioassays. A mixture of phenolic acids similar to that obtained from wheat-no-till soils did not affect germination of clover or morning glory and radicle and hypocotyl length of morning glory. The mixture did, however, reduce radicle and hypocotyl length of clover. Individual phenolic acids also did not inhibit germination, but did reduce radicle and hypocotyl length of both species. 6-MBOA (6-methoxy-2,3-benzoxazolinone), a conversion product of 2-o-glucosyl-7-methoxy-1,4-benzoxazin-3-one, a hydroxamic acid in living wheat plants, inhibited germination and radicle and hypocotyl length of clover and morning glory. 6-MBOA, however, was not detected in wheat debris, stubble, or soil extracts. Total phenolic acids (FC) in extracts were determined with Folin and Ciocalteu's phenol reagent. Levels of FC in wheat-conventionaltill soil extracts were not related to germination or radicle and hypocotyl length of either species. Levels of FC in wheat-no-till soil extracts were also not related to germination of clover or morning glory, but were inversely related to radicle and hypocotyl length of clover and morning glory. FC values, solute potential, and acidity of wheat-no-till soil extracts appeared to be independent (additive) in action on clover radicle and hypocotyl length. Radicle and hypocotyl length of clover was inversely related to increasing FC and solute potential and directly related to decreasing acidity. Biological activity of extracts was determined best from slopes of radicle and hypocotyl length obtained from bioassays of extract dilutions. Thus, data derived from the water-autoclave extraction procedure, FC analysis, and slope analysis for extract activity in conjunction with data on extract pH and solute potential can be used to estimate allelopathic activity of wheat-no-till soils.}, number={12}, journal={JOURNAL OF CHEMICAL ECOLOGY}, author={BLUM, U and GERIG, TM and WORSHAM, AD and HOLAPPA, LD and KING, LD}, year={1992}, month={Dec}, pages={2191–2221} }
 @article{blum_rebbeck_1989, title={INHIBITION AND RECOVERY OF CUCUMBER ROOTS GIVEN MULTIPLE TREATMENTS OF FERULIC ACID IN NUTRIENT CULTURE}, volume={15}, ISSN={["0098-0331"]}, DOI={10.1007/BF01015187}, abstractNote={Ferulic acid, a frequently cited allelopathic agent, inhibited photosynthesis, leaf expansion, and root elongation of cucumber seedlings grown in aerated nutrient cultures in a growth chamber. Other effects were a reduction in the proportion of radioactivity fixed by photosynthesis translocated to roots, a stimulation in secondary root initiation, and an increase in root-shoot ratios. Inhibition of leaf expansion and root elongation induced by multiple ferulic acid treatments was rapidly lost once ferulic acid was removed from the root environment. The changes in general root morphology, i.e., average root length and root number, associated with ferulic acid treatments, were partially reversed or not affected when ferulic acid was removed from the root environment.}, number={3}, journal={JOURNAL OF CHEMICAL ECOLOGY}, author={BLUM, U and REBBECK, J}, year={1989}, month={Mar}, pages={917–928} }
 @article{blum_mrozek_johnson_1983, title={INVESTIGATION OF OZONE (O3) EFFECTS ON C-14 DISTRIBUTION IN LADINO CLOVER}, volume={23}, ISSN={["0098-8472"]}, DOI={10.1016/0098-8472(83)90013-8}, abstractNote={Ladino clover plants were exposed to 0, 0.05, 0.10 or 0.15 ppm O3 for 4 hr per day for 6 days starting 32 days after planting. Leaf injury was estimated and 14CO2 exposures were given 48 hr after the last O3 exposure. One mature leaf per plant with visible injury roughly equivalent to whole plant injury was exposed to 14CO2 in a plexiglass chamber for 15 min. Twenty-four hours later, plants were harvested, placed on herbarium sheets, frozen and freeze-dried. Radioautographs were subsequently used to determine the distribution of 14C and as a guide in partitioning plant material for quantification of radioactivity. Ozone exposures reduced root dry weight more than shoot dry weight of ladino clover. The maximum reduction for shoot dry weight was 24% while the maximum reduction for root dry weight was 42%. Total plant radioactivity values, determined 24 hr after the 14CO2 exposure, indicated that increasing O3 concentrations reduced net photosynthesis of clover plants. The proportion of carbon allocated to the roots increased gradually from 35 to 52% with increasing O3 levels up to 0.10 ppm and then decreased rapidly to 21% at 0.15 ppm. Carbon allocation to developing leaves decreased from 64 to 48% with increasing O3 levels up to 0.10 ppm and then increased to 79% at 0.15 ppm.}, number={4}, journal={ENVIRONMENTAL AND EXPERIMENTAL BOTANY}, author={BLUM, U and MROZEK, E and JOHNSON, E}, year={1983}, pages={369–378} }
 @article{blum_heagle_burns_linthurst_1983, title={THE EFFECTS OF OZONE ON FESCUE-CLOVER FORAGE - REGROWTH, YIELD AND QUALITY}, volume={23}, ISSN={["1873-7307"]}, DOI={10.1016/0098-8472(83)90029-1}, abstractNote={A fescue—clover stand (Festuca arundinacea Schreb. cv. Kentucky 31 and Trifolium repens L. cv. Tillman) was established in November of 1977. Plants were grown and exposed to ambient air (ambient air plots), and in open-top chambers to charcoal-filtered air, nonfiltered air with enough O3 added for 7 hr per day (0930–1630 hr EDT) to compensate for losses associated with the air-handling system (NF-1), or enough O3 added to approximate 0.03 ppm above ambient concentrations (NF-2). Plants were cut to 7.5 cm whenever they reached a height of 20 cm. The effects of O3 on the regrowth of clover and fescue varied with season and year. Ozone had a greater negative impact on clover than on fescue. Annual forage yield of the fescue—clover mixture was reduced 14% (NF-1) and 27% (NF-2) in 1979. Fescue regrowth was enhanced by O3 for one growth period in 1978 and 1979. Ozone reduced % N and % estimated digestibility of clover for various growth periods during 1978 and 1979. Percent N of fescue was increased by O3 for several growth periods during 1978 and reduced for several growth periods in 1979. Percent estimated digestibility of fescue was reduced for one growth period in 1979. The maximum change for % N was 1.5% and for estimated digestibility 7%. The O3 induced yield reductions of clover (22% for NF-1 and 54% for NF-2 in 1979) from the fescue—clover pasture also decreased forage quality. The differential growth responses of clover to O3 in 1978 and 1979 appeared to be associated with drought. Data suggest that ambient levels of O3 in the south-eastern U.S. can have a negative impact on forage quality and quantity of fescue-ladino clover pastures.}, number={2}, journal={ENVIRONMENTAL AND EXPERIMENTAL BOTANY}, author={BLUM, U and HEAGLE, AS and BURNS, JC and LINTHURST, RA}, year={1983}, pages={121–132} }
 @article{blum_smith_fites_1982, title={EFFECTS OF MULTIPLE O-3 EXPOSURES ON CARBOHYDRATE AND MINERAL CONTENTS OF LADINO CLOVER}, volume={22}, ISSN={["0098-8472"]}, DOI={10.1016/0098-8472(82)90033-8}, abstractNote={Ladino clover plants of various ages were exposed for 5 consecutive days for 6 hr/day to either carbon-filtered air or 0.1 ppm O3 during one of two growth periods (August or April). The plants were grown during June–August and during January–April. Plants were harvested 1 week after receiving the final O3 exposure. Ozone reduced root, shoot and plant dry weights and total non-structural carbohydrate (TNC, mg/g). Root TNC was not modified by O3. When O3 induced reductions were expressed on a per cent basis, the reductions were identical for the two experimental growth periods. Plant size and TNC content were greater for plants grown during the January–April growth period whereas mineral content (% or ppm) was greater plants from June to August. When mineral content was altered by O3 (and this varied with growth period), O3 increased mineral content except for reductions in plant Na (during June–August growth period) and shoot S (determined only for January–April growth period). The potential effects of multiple O3 exposures on forage quality and quantity are discussed.}, number={2}, journal={ENVIRONMENTAL AND EXPERIMENTAL BOTANY}, author={BLUM, U and SMITH, GR and FITES, RC}, year={1982}, pages={143–154} }
 @article{blum_heck_1980, title={EFFECTS OF ACUTE OZONE EXPOSURES ON SNAP BEAN AT VARIOUS STAGES OF ITS LIFE-CYCLE}, volume={20}, ISSN={["0098-8472"]}, DOI={10.1016/0098-8472(80)90222-1}, abstractNote={Snap beans (Phaseolus vulgaris L. ‘BBL-290’) were exposed to ozone (O3) at 0 (carbon-filtered air), 30 and 60 pphm for two 1.5 h periods that were 3 days apart. Plants were exposed to O3 at six different stages (8+11, 14+17, 20+23, 26+29, 32+35, or 38+41 days after seeding). Half of the plants were harvested 7 days after the second exposure and the other half were harvested 48 days after planting. Ozone reduced relative growth rate, absolute growth rate, pod production, nodulation, and total nitrogen content, but increased the amount of nitrogen per gram of plant tissue. The magnitude of these responses of growth, nodulation and nitrogen content varied with the O3 concentration and plant age at the time of exposure. Recovery of growth and nodulation at the final harvest was partial for plants exposed at 8+11 and 14+17 days. Nitrogen content was correlated with both plant dry weight (root + top dry wt; r2 = 0.95) and nodule number (r2 = 0.93). These relationships were described by exponential equations.}, number={1}, journal={ENVIRONMENTAL AND EXPERIMENTAL BOTANY}, author={BLUM, U and HECK, WW}, year={1980}, pages={73–85} }