Spatial Distribution of Ethylene Production by Individual Needles Along a Shoot ofPinus sylvestrisL.: Relationship with Peroxidase Activity

Spatial distribution of ethylene production by individual currentyear needles and the relationship with peroxidase activity wasstudied along a shoot of Scots pine (Pinus sylvestrisL.). Muchvariation in ethylene production between and within individualseedlings was found. There was a significant difference in meanintensity of ethylene production between orthostichies withinindividual seedlings. The capacity of individual needles toconvert 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylenedid not correlate with the basal rate of ethylene production.Mean ethylene production intensity by orthostichies correlatedpositively with mean peroxidase activity. A positive correlationbetween the intensity of ethylene production by individual needlesand detachment-induced peroxidase activity was found. The datasuggests that the rate of ethylene production by individualneedles may be directly related to their peroxidase activityand at least in part to their antioxidative capacity.Copyright1998 Annals of Botany Company Pinus sylvestris,pine, ethylene production, spatial distribution, individual needles, peroxidase, seasonal changes.     

Changes in intracellular localization of peroxidase during Microsporogenesis in Gymnosperms

Cytochemical investigations on peroxidase localization during microsporogenesis inLarix europaea D.C.,Taxus baccata L. andPinus sylvestris L. have revealed striking differences in the localization and activity level of this enzyme linked with the developmental stage. The localization and level of activity of peroxidase, typical of each stage, changed in the course of microsporogenesis in a strictly orderly way, giving a characteristic and stable pattern. The pattern of intracellular peroxidase localization proved to be the same for microsporogenesis of all the gymnosperms in question. It is suggested that the identity of that pattern in plants so phylogenetically distant asTaxus baccata L. andPinus sylvestris L. indicates that peroxidase activity in gymnosperms’ microsporogenesis is connected with the fundamental and genetically well stabilized processes of meiotic cytodifferentiation. Moreover, enhanced peroxidase activity has been found in the sites of callose walls synthesis of dyads and tetrads, which suggests the participation of this enzyme in callose synthesis.     

Peroxidase activity in the leaf elongation zone of tall fescue : I. Spatial distribution of ionically bound peroxidase activity in genotypes differing in length of the elongation zone

Cessation of cell expansion has been associated with cell wall cross-linking reactions catalyzed by peroxidase. This study utilized two genotypes of tall fescue (Festuca arundinacea Schreb.) that differ in length of the leaf elongation zone to investigate the relationship between ionically bound peroxidase activity and the spatial distribution of leaf elongation. Peroxidase activity was also localized histochemically in transverse sections of the leaf blade using 3,3′ -diaminobenzidine. Soluble or soluble plus ionically bound peroxidase activities were extracted from homogenized segments of the elongating leaf blade and assayed spectrophotometrically. Activity of the ionically bound fraction, expressed per milligram fresh weight or per microgram protein, increased as cells were displaced through the distal half of the elongation zone, corresponding to the region in which the elongation rate declined. In both genotypes, the initial increase in activity preceded the onset of growth deceleration by about 10 hours. In the basal region where elongation began, histochemical localization showed that peroxidase activity was found only in vascular tissues. As cells were displaced farther through the elongation zone, peroxidase activity appeared in walls of other longitudinally continuous tissues such as the epidermis and bundle sheaths. Increase in ionically bound peroxidase activity and changes in localization of peroxidase activity occurred at comparable developmental stages in the two genotypes. The results indicate that cessation of elongation followed an increase in cell wall peroxidase activity.     

Distribution and population genetic structure of the Mediterranean pine shoot beetle Tomicus destruens in the Iberian Peninsula and Southern France

1 The Mediterranean pine shoot beetle Tomicus destruens has long been indistinguishable from its congeneric Tomicus piniperda. Both species attack pines, and can be found in sympatry. The geographical distribution of T. destruens is still unclear in most of the Mediterranean Basin. 2 We aimed to describe the geographical distribution and zones of sympatry of both species in the Iberian Peninsula and France, and to study the molecular phylogeographical pattern of T. destruens. 3 Tomicus spp. adults were sampled in Portugal, Spain and France, and a portion of the mitochondrial genes COI and COII was sequenced for 84 individuals. Sequences were aligned to a data set previously obtained from French localities. 4 Tomicus destruens was found in all populations, except for one locality in Portugal and in the Landes (France). It was in sympatry with T. piniperda in two locations on Pinus pinaster and one location on Pinus radiata. 5 Within‐population genetic diversity was high, but we found a significant pattern of spatial distribution of genetic variation, as well as a significant effect of the host tree. 6 The data suggest the existence of two glacial refugia, from which T. destruens recolonized its current range. One refugium was located in Portugal where the beetle probably evolved on P. pinaster. The corresponding haplotypes show a West–East frequency gradient. The other refugium was probably in the eastern range, where the beetles evolved on Pinus halepensis and P. pinea. The corresponding haplotypes show an East–West frequency gradient.     

Fungal elicitor-mediated responses in pine cell cultures

A tissue culture system has been developed to examine phenylpropanoid metabolism induced in pine tissues by an ectomycorrhizal symbiont. An elicitor preparation from the ectomycorrhizal fungus Thelephora terrestris Fr. induced enhanced phenolic metabolism in suspension cultured cells of Pinus banksiana Lamb., as indicated by tissue lignification and accumulation of specific methanol-extractable compounds in the cells. Induction of lignification was observed as early as 12 h after elicitation. The activity of phenylalanine ammonia-lyase (PAL, EC 4.3.1.5), the entry-point enzyme into phenylpropanoid metabolism, also increased within the same time-frame in elicited cells. Significant increases in PAL activity were evident by 6 h after elicitation, and, by 12 h after elicitation, PAL activity in elicited cells was ten times greater than that in the corresponding controls. Lignification of the elicited tissue was also accompanied by an increase in the activity of other enzymes associated with lignin synthesis, including caffeic acid O-methyl transferase (EC 2.1.1.46), hydroxycinnamate:CoA ligase (EC 6.2.1.12), cinnamyl alcohol dehydrogenase (EC 1.1.1.-), coniferin glucosidase (EC 3.2.1.21) and peroxidase (EC 1.11.1.7). The increase in total peroxidase activity was associated with a change in the pattern of soluble peroxidase isoforms. The pine cell culture-ectomycorrhizal elicitor system provides a good model for molecular analysis of the process of lignification in an economically important softwood species.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - 4CL hydroxycinnamate:Coenzyme A ligase (EC 6.2.1.12) - CAD cinnamyl alcohol dehydrogenase (EC 1.1.1.-) - COMT S-adenosyl-l-methionine:caffeate O-methyl transferase (EC 2.1.1.46) - HPLC high-pressure liquid chromatography - PAL phenylalanine ammonia-lyase (EC 4.3.1.5) - TGA thioglycolic acid To whom correspondence should be addressedFinancial assistance for this work was provided by the Natural Sciences and Engineering Research Council of Canada.     

Neodiprion sertifer defoliation causes long-term systemic changes of oxidative enzyme activities in Scots pine needles

The aim of the experiments reported here was to study possible long-term effects of Neodiprion sertifer Geoff. (Hymenoptera: Diprionidae) herbivory, or artificial defoliation, on oxidative enzyme activities in Scots pine (Pinus sylvestris L.) needles as a consequence of induced defense responses. During year 1 (the first season), defoliation by N. sertifer, which feeds on previous season’s needles, did not result in statistically significant changes in polyphenol oxidase activity in the current year’s needles. In contrast, defoliation did lead to increased peroxidase activity in those needles. In the second season (year 2) N. sertifer defoliation of pine seedlings, also defoliated in the previous season either by larvae or artificially, resulted in a decrease of peroxidase activity in the current year’s needles. No significant differences between treatments carried out in year 1 were found in year 2 for peroxidase activity in the previous year’s needles. However, defoliation in year 1 by N. sertifer resulted in decreased needle consumption, and higher mortality of larvae, in year two. These results indicate the existence of long-term changes in needle oxidative enzyme activities as a consequence of N. sertifer feeding.     

Identifying the abiotic and biotic drivers behind the elevational distribution shift of a parasitic plant

• Climate change will alter the biotic and abiotic environment and dissipate ecological barriers, reorganising maps of current distribution of parasites and their hosts. In this study, we analyse the population dynamics of the parasitic plant Viscum album subsp. austriacum and explore key biotic (host availability and seed dispersal) as well as abiotic (temperature) factors influencing elevational distribution.
• The study was conducted along an elevational gradient of a Mediterranean mountain, covering the distribution belts of three potential pine hosts: Pinus halepensis (1300–1500 m), P. nigra (1300–1900 m) and P. sylvestris var. nevadensis (1600–2000 m). Along this gradient, we measured multiple variables of mistletoe population (prevalence, abundance and demographic profile) and different factors that might define the current mistletoe distribution (host suitability and availability, temperature and seed dispersal services).
• We found a decline in mistletoe prevalence and abundance with increasing elevation, detecting larger values of both variables at lower elevations of the most suitable host (Pinus nigra). Pinus sylvestris var. nevadensis was a suboptimal but suitable host for the parasite at high elevations. Mistletoe found suitable temperatures and seed dispersal services all along the gradient, being able to recruit at any site.
• With warming temperatures, the presence of suitable vectors for parasite dispersion, and the presence of a sub‐optimal host (P. sylvestris var. nevadensis) at the mountain top, mistletoe currently has a window of opportunity to expand its present geographic distribution to the summits.

     

Changes in Peroxidase Activity Associated with Cell Walls During Pine Hypocotyl Growth

Peroxidase active against 2,2'-azino-bis-[3-ethylbenzthiazoline-6-sulphonicacid] (ABTS) and guaiacol were found in the apoplastic fluid,as well as ionically and covalently associated with pine cellwalls. The highest activity was found covalently bound to cellwalls, while the lowest activity was in the apoplastic fluid.Both ABTS and guaiacol peroxidases increased with the hypocotylage in the three fractions, apoplastic, ionically and covalentlybound. Furthermore, the changes in both peroxidases along thehypocotyl were also studied. Both apoplastic ABTS- and guaiacol-peroxidasesincreased from the apical towards the basal region of the hypocotylsof 10-d-old seedlings. A relation between peroxidase activityin the apoplastic fluid and the cell wall stiffening in pinehypocotyls is proposed.Copyright 1995, 1999 Academic Press Cell wall, growth, hypocotyl, peroxidase, pine, Pinus pinaster Aiton     

Distribution of isoflavones in lupin hypocotyls. Possible control of cell wall peroxidase activity involved in lignification

The distribution of 4 key isoflavones (luteone, genistein, 2'-hydroxygenistein and wighteone) in lupin ( Lupinus albus L. cv. multolupa) hypocotyls shows a gradient that diminishes from young to old tissues. A spatial gradient occurs within the hypocotyl, and a temporal gradient in both the outermost vascular and epidermal tissues. Not only does a gradient exist in respect to the quantity of isoflavones, but there is also a gradient in respect to the type of isoflavone. Thus, wighteone is mainly associated with the non-meristematic zones of the lupin hypocotyl. A close relationship was found between the distribution and the localization in the walls of phloem cells of both peroxidase (EC 1.11.1.7) and isoflavones. This observation suggests an in vivo peroxidase-isoflavone interconnection. In fact, lupin isoflavones are able to inhibit the peroxidase-catalyzed oxidation of the lignin precursor coniferyl alcohol, probably due to the co-oxidation of isoflavones in the reaction media. The results are discussed on the basis of a possible role for isoflavones in controlling cell wallperoxidase activity involved in the lignification of phloem cells.     

Seasonal changes in plasma membrane H<Superscript>+</Superscript>-ATPase activity of <Emphasis Type="Italic">Vaccinium myrtillus</Emphasis> (L.) and <Emphasis Type="Italic">Pinus sylvestris</Emphasis> (L.)

Seasonal changes in vanadate sensitive plasma membrane H⁺-ATPase activity of bilberry (Vaccinium myrtillus L.) and Scots pine (Pinus sylvestris L.) were studied in a period from February to August in northern Finland. The plasma membrane isolation was performed by sucrose gradient centrifugation, and the H⁺-ATPase activity was assayed by spectrophotometrical determination of released inorganic phosphate. The studied species showed seasonal changes from high winter to low spring activity, indicating probable physiological changes between hardened and dehardened tissue. ATPase activity of bilberry peaked up at the beginning of the growth period, obviously due to active phloem loading of photosynthates.     

Peroxidase activity of desiccation-tolerant loblolly pine somatic embryos

Summary Desiccation tolerance can be induced by culturing somatic embryos of loblolly pine (Pinus taeda L.) on medium supplemented with 50 μM abscisic acid (ABA) and/or 8.5% polyethylene glycol (PEG₆₀₀₀). Scanning electron microscopy of desiccated somatic embryos showed that the size and external morphology of the desiccation-tolerant somatic embryos recovered to the pre-desiccation state within 24–36 h, whereas the non-desiccation-tolerant somatic embryos did not recover and remained shriveled, after rehydration. Peroxidase activity of desiccated somatic embryos increased sharply after 1 d of desiccation treatment at 87% relative humidity (RH), and desiccation-tolerant somatic embryos had higher peroxidase activity compared to sensitive somatic embryos. Higher peroxidase activity of desiccation-tolerant somatic embryos may have allowed them to catalyze the reduction of H₂O₂ produced by drought stress, and protected them from oxidative damage.     

Effect of culture temperature on the heterologous expression of <Emphasis Type="Italic">Pleurotus eryngii</Emphasis> versatile peroxidase in <Emphasis Type="Italic">Aspergillus</Emphasis> hosts

Production of recombinant versatile peroxidase in Aspergillus hosts was optimized through the modification of temperature during bioreactor cultivations. To further this purpose, the cDNA encoding a versatile peroxidase of Pleurotus eryngii was expressed under control of the alcohol dehydrogenase (alcA) promoter of Aspergillus nidulans. A dependence of recombinant peroxidase production on cultivation temperature was found. Lowering the culture temperature from 28 to 19 °C enhanced the level of active peroxidase 5.8-fold and reduced the effective proteolytic activity twofold. Thus, a maximum peroxidase activity of 466 U L^-1 was reached. The same optimization scheme was applied to a recombinant Aspergillus niger that bore the alcohol dehydrogenase regulator (alcR), enabling transformation with the peroxidase cDNA under the same alcA promoter. However, with this strain, the peroxidase activity was not improved, while the effective proteolytic activity was increased between 3- and 11-fold compared to that obtained with A. nidulans.     

酚酸物质对红松种子萌发及苗木生长和生理特性的影响

通过室内模拟试验,阐明阔叶红松林中已测得含量较高的3种酚酸物质（苯甲酸、丁香酸和香草酸）对红松种子萌发及苗木生长的影响,为探索阔叶红松林内化感作用机理及解决红松更新障碍问题提供科学依据。采用培养皿培养法及室内盆栽培养法,以红松种子和3年生红松苗为试验对象,设置不同浓度（2、20、200 mg/L）苯甲酸、丁香酸、香草酸处理液,以蒸馏水为对照（CK）,进行红松种子萌发试验及红松苗木生长试验,研究3种酚酸物质对红松种子发芽、苗木生长、光合色素、抗氧化酶活性、膜脂过氧化作用及渗透调节物质的影响。结果表明,（1）不同浓度3种酚酸均抑制红松种子萌发,但酚酸浓度变化仅对红松种子发芽率影响差异显著。（2）3种酚酸对红松苗木生长及物质积累抑制作用显著。浓度变化对红松苗株高及地径影响不显著,对生物量、根干重和茎干重影响显著。（3）针叶叶绿素a、叶绿素b、类胡萝卜素含量变化对酚酸处理反应一致,20 mg/L的3种酚酸均显著抑制光合色素产生,而200 mg/L丁香酸溶液及2 mg/L香草酸溶液均显著促进叶绿素a和类胡萝卜素积累。（4）酚酸处理使红松苗针叶中POD、CAT活性降低,SOD活性增加。针叶中MDA含量显著增加,200 mg/L丁香酸溶液处理组针叶MDA含量高于CK处理组70.51%。（5）不同浓度苯甲酸溶液促进可溶性糖增加,抑制可溶性蛋白增加;不同浓度丁香酸溶液促进可溶性蛋白增加,而不同浓度香草酸溶液抑制可溶性蛋白增加,二者对可溶性糖含量影响受浓度变化影响显著。苯甲酸、丁香酸、香草酸影响红松种子萌发,通过对红松苗光合色素、抗氧化酶活性及渗透调节物质的影响导致其生长受抑制、生物量减少,产生膜脂过氧化伤害。因此,解决阔叶红松林内红松更新障碍问题时,凋落物及土壤中酚酸物质的化感作用不容忽视。     

Analysis of the distribution of epiphytic lichens within homogeneousFagus sylvatica stands along an altitudinal gradient (Mount Olympos,Greece)

Epiphytic lichen vegetation onFagus sylvatica sas studied in 4 sites along an altitudinal gradient from 930 to 1500 m on SE facing slopes of Mount Olympos (Greece). The crucial factor determining the spatial heterogeneity of epiphytic lichens onF. sylvatica is the altitude and not the height on the trunk at which lichen community is established. 17 out of 26 taxa are confined to a particular elevation range, while another three are clearly ubiquitous in their distribution. The number of lichen species at breast height is higher than at the base of the trunks. The results were compared with those gathered earlier in an analogous study on the vertical distribution of epiphytic lichens onPinus nigra along an altitudinal gradient from 750 to 1510 m of the same mountain. Comparison suggests that spatial heterogeneity of epiphytic lichens onF. sylvatica is different from the one onP. nigra.     

The origin of remnant forest stands of Pinus tabulaeformis in southeastern Inner Mongolia

Pinus tabulaeformis is an endemic species in northern China. The northern edge of its distribution corresponds to the northern margin of the monsoon climate. Several stands of Pinus tabulaeformis beyond its major range of distribution were found on the southeastern edge of the Inner Mongolia Plateau. Phytosociological analysis shows that the community structure, species composition and regeneration ability of Pinus trees in these stands are quite different from those within its continuous range of distribution. This paper presents palynological evidence to explain how and when these remnant communities were formed. Pinus tabulaeformis entered the study area in the mid-Holocene as the summer monsoon intensified, and declined when the summer monsoon weakened. Climatic change was the driving factor for the migration of Pinus tabulaeformis. It might be supposed that the competition between pine and oak forest during the mid-Holocene warm period also affected the immigration of pine. The remnant stands of Pinus tabulaeformis were apparently favored by the microhabitat of the sandy soils in valleys when the climate became drier. The remnant stands of Pinus tabulaeformis help stabilize the stand dunes. The protection of these stands is an important task of natural conservation in the study area.     

Early effects of phenolic compounds, extracted from two forest litters, on ammonium uptake and assimilation in Pinus laricio and Pinus pinaster seedlings

The early effects of low molecular weight phenolic compounds, released by Pinus laricio and Pinus pinaster litter, on ammonium uptake and its assimilation in two Pinus species were studied. In Pinus laricio seedlings, the exposure to phenols extracted from Pinus laricio litter increased not only the ammonium uptake but also the activity of the main enzymes involved in its assimilation, whereas the phenols extracted from Pinus pinaster litter had a negative effect on these metabolic processes. In Pinus pinaster seedlings, the exposure to both phenols decreased the ammonium uptake and the activity of the main enzymes involved in its assimilation. Histological analysis carried out in Pinus laricio roots showed that phenols extracted from Pinus laricio litter induced the greatest growth of cortex, element through which occurs the ions uptake in plants, whereas phenol extracted from Pinus pinaster litter inhibited cortex development. On the other hand, in Pinus pinaster seedlings the observation showed that both phenols inhibited cortex growth indicating a strict correlation between cortex development and ammonium uptake and its assimilation.     

Seasonal fluctuations in soil phenolics of a coniferous forest: effects on seed germination of different coniferous species

This study examined seasonal variations in the content of water-soluble phenolics extracted from litter and Ah horizon of forest soil under Pinus laricio Poiret trees. After having identified and quantified different phenolics, the effects of seasonal phenolic extracts, single phenolic acids and synthetic phenol mixtures on seed germination of Pinus laricio Poiret, Pinus pinaster Aiton and Pinus halepensis Mill. were evaluated, and the activity of phenolics on the main enzymes involved in the glyoxylate cycle was tested. The results indicated a seasonal variation of phenol content in soil, with largest concentrations of water-soluble phenolic acids in autumn and smallest concentrations in summer. Addition of phenol extracts to germination medium reduced seed germination showing phytotoxic effects which differed, depending on the species and the fractions tested. Phenols extracted from litter and Ah horizon in autumn and winter, vanillic acid, and synthetic mixtures reproducing phenols extracted from soil in winter inhibited seed germination of Pinus laricio, pinaster and halepensis more than other treatments. A greater inhibitory effect was observed on seed germination of Pinus pinaster and halepensis compared to Pinus laricio. The phenols also had the greatest inhibitory effect on glyoxylic enzyme activities. Section Editor: H. Lambers     

PHENOLIC COMPOUNDS ASSOCIATED WITH DEVELOPMENT IN THE LIVERWORT MARCHANTIA POLYMORPHA

Extracts of Marchantia polymorpha contain substances which, in vitro, strongly inhibit or enhance indoleacetic acid oxidation by both horseradish peroxidase and an IAA oxidase enzyme from M. polymorpha. The extracts can be partially freed of such activity by dialysis, passage through a column of polyvinylpyrrolidone powder, or extraction with an anion exchange resin. Chromatographic separation of the extract revealed the presence of four as yet unidentified phenolic compounds. Two inhibited and two enhanced IAA oxidase activity. Inhibitory activity was not destroyed by horseradish peroxidase in the absence of IAA. The level of these compounds in various regions of thallus was measured. Inhibitors were present throughout the tissue, with some localization in the basal and apical areas; there was an acropetal gradient of increasing cofactor concentration.     

Spatial Distribution of Lectin Activity in Perilesional Areas of Tobacco Leaves Inoculated with Tobacco Mosaic Virus

The activities of lectins and peroxidase and lignin content were studied in the perilesional area of leaves in two tobacco species (Nicotiana tabacumL., cultivar Samsun NN, and N. glutinosa L.) inoculated with tobacco mosaic virus. The development of hypersensitivity response proved to be accompanied by a complex spatial and temporal distribution of lectin activity. The area 5–9 mm away from the lesion center was characterized by the highest activity of loosely bound membrane lectins eluted with 0.05% Triton X-100. In the fraction of tightly bound membrane lectins (eluted with 0.5% detergent), lectin activity decreased during the first two days but increased on day 4 after inoculation. The activity of loosely bound membrane lectins increased in the leaf areas distant from the lesion. Two-phase dynamics in the interlesional area were also observed for lectin activity in the tightly bound membrane fraction (decrease on day 2 days and increase on day 4 after inoculation) and for peroxidase activity (increase on day 2 days and decrease on day 4). The relationship between the dynamics and spatial distribution of lectins in the perilesional area and the possible involvement of these proteins in pathogen-induced changes in photosynthesis are discussed.     

The effects of various nutrients on extracellular peroxidases and acid-precipitable polymeric lignin production byStreptomyces chromofuscus A2 andS. viridosporus T7A

Summary The relationships between growth, medium pH, assimilation of glucose and amino acids, presence or absence of lignocellulose in the medium, lignin solubilization, and the appearance of extracellular peroxidase activity were compared for two lignin-solubilizing actinomycetes, Streptomyces chromofuscus A2 and S. viridosporus T7A. In a mineral salt medium containing yeast extract and three amino acids S. chromofuscus A2 grew faster than S. viridosporus T7A. When d-glucose was added to this medium, it was used in preference to the amino acids, the assimilation of which was delayed. Extracellular peroxidase activity peaked during the stationary phase, and glucose supplementation delayed peroxidase production. The eventual peak in peroxidase activity was higher in glucose-containing medium than in medium without glucose. Supplementation of the medium with lignocellulose did not affect either the level or time of appearance of extracellular peroxidase. However, lignin solubilization in lignocellulose-supplemented medium correlated positively with peroxidase activity: both increased after the cells entered the stationary phase. Supplementation of lignocellulose-containing medium with glucose delayed peroxidase production and lignin solubilization until the glucose had been assimilated. With S. viridosporus T7A, addition of d-glucose to the standard medium affected amino acid assimilation differently from S. chromofuscus A2. Glucose was consumed concomitantly with the amino acids. In the medium supplemented with lignocellulose, peroxidase activity and lignin solubilization correlated as they did for S. chromofuscus A2. A correlation of unknown significance was observed between the peroxidase activities of both strains and increasing medium pH. S. chromofuscus A2 produced more peroxidase and solubilized more lignin from lignocellulose than did S. viridosporus T7A. Overall, these findings show that extracellular peroxidases of both Streptomyces ssp. appear extracellularly primarily after cells cease growing and nutrients have been depleted from the medium. Also, increasing extracellular peroxidase activity and rates of lignin solubilization in both organisms are correlated and subject to glucose repression. These results point to the involvement of stationary-phase active peroxidases in the Streptomyces-catalyzed solubilization of lignin.Paper No. 90518 of the Idaho Agricultural Experiment Station Offprint requests to: D. L. Crawford