The respiratory metabolism of selected lumbricidae

Summary Open-system infra red gas analysis was used to measure the CO₂ output throughout a year of four species of earthworm. The respiratory quotients (R.Q.s) of the four species were determined by means of a Warburg apparatus and it was found that they varied with season. In some instances R.Q.s did not fall within the expected range of 0.7 to 1.0 and the low values were attributed to calciferous gland activity and the fixation of metabolic CO₂.The results from CO₂ output measurements at 10°C and R.Q.s were used to calculate oxygen uptake, this varied seasonally but the mean annual values at 10°C for adult, large immature and small immature A. rosea were 64.17, 72.66 and 78.56 l O₂ g^-1 fresh wt h^-1 respectively. Mixed size groups of L. castaneus had a mean annual oxygen consumption at 10°C of 155.83 l O₂ g^-1 fresh wt h^-1 and equivalent values for D. rubida and O. cyaneum were 112.02 and 69.35 l O₂ g^-1 fresh wt h^-1. The apparent relationship between a high respiratory rate per unit weight and a litter dwelling habit (e.g. L. castaneus and D. rubida) disappeared when allowance was made for the weight of gut contents. Mean annual values for oxygen uptake in l O₂ g^-1 gut free fresh wt h^-1 at 10°C were L. castaneus (194.79), D. rubida (142.22), A. rosea (95.70) and O. cyaneum (139.28). No size specific metabolism could be demonstrated either within or between species, this is believed to be correlated with the different levels of activity shown by different species and their life stages.Rates of oxygen consumption per unit weight for A. rosea were shown to be proportional to ambient temperature. Q ₁₀ slopes of this relation, between 6 and 15°C, were higher for large immature A. rosea (2.42) and small immatures (1.96) than for adult clitellate worms (1.42). The mean Q ₁₀ relationship for all size classes of A. rosea was 1.93 over the same temperature range and the equivalent value for cocoons was 1.63. The relationship between the oxygen consumption rate of all size classes of A. rosea and ambient temperature was not significantly affected by acclimatisation at 5 and 10° C prior to measurements being made at 6, 10 and 15° C.     

Biological removal of inorganic Hg(II) as gaseous elemental Hg(0) by continuous culture of a Hg-resistant Pseudomonas putida strain FB-1

A strain of broad-spectrum, mercury-resistant Pseudomonas putida FB1 was used to remove mercury as the gaseous element (Hg(0)) from a continuous axenic culture, fed with a synthetic medium containing 1 mg Hg l^-1 as HgCl₂. Mercury determinations were performed in steady-state cultures using various culture fractions [whole culture, filtered supernatant, bacterial cells (dry wt), recovery trap liquid] in order to determine the removal efficiency at different dilution rates (from 0.1 to 3.0 day^-1). The removal efficiency ranged from 99.2% to 99.8%, and the residual Hg was maintained below 5 l^-1 (the maximum allowable concentration of Hg in liquid wastes according to Italian law) at a dilution rate of 1.0 day^-1, corresponding to a Hg flux of 40 g l^-1 h^-1. Hg accumulation by cell biomass was negligible for dilution rates under 1.0 day^-1. A progressive accumulation of Hg, both in the liquid phase and in cells, occurred at a higher dilution rate (3.0 day^-1; close to washout), corresponding to a Hg concentration of 25 g g^-1 (dry wt). The estimated K_m and V_max for Hg reduction were 0.241 mg l^-1 and 9.5 mg g^-1 h^-1, respectively. In batch experiments maximum Hg removal occurred at the optimum growth temperature (28°C) of P. putida. The maximum recovery of Hg in the liquid trap was 78%.     

Production of plumbagin from cell cultures of Plumbago rosea L.

Callus and suspension cultures derived from leaf explants of Plumbago rosea were established and plumbagin, a naphthoquinone, was isolated from them and confirmed by ¹H NMR and electron-ionization mass spectroscopy. Maximum content of plumbagin was obtained in the stationary phase of growth (4.3 mg g^–1 dry cell wt). Media pH, phytohormones and carbon sources were optimized for biomass and plumbagin accumulation. Cell aggregates, measuring 500 m in diam, produced 8.2 g dry cell wt l^–1, but larger aggregates (above 500 m) favored plumbagin accumulation with an yield of 4.5 mg g^–1 dry cell wt.     

Accelerated degradation of <Emphasis Type="Italic">N,N′</Emphasis> (DBU) upon repeated application

In a recent study on the degradation of N,N-dibutylurea (DBU), a breakdown product of benomyl [methyl 1-(butylcarbamoyl)-2-benzimidazole carbamate], the active ingredient in Benlate^® fungicides, degradation half-lives of 1.4–46.5days were observed across several soils incubated at various combinations of soil moisture potential (–0.03 and –0.1MPa) and temperature (23, 33, and 44°C) for a single DBU application of 0.08 and 0.8 g g^–1 (Lee et al. 2004). However, Benlate^® can be applied as often as every 7days resulting in the repeated application of DBU likely to be present in the Benlate^® over a growing season. In this study, the effect of seven repeated DBU applications on mineralization rate was investigated in two soils, which encompass the range in rates previously observed. For the slower degrading soil, repeated DBU application increased mineralization from 0.029 to 0.99day^–1 at the 0.08 g g^–1 rate, and 0.037 to 0.89day^–1 at the 0.8 g g^–1 rate. For the faster degrading soil, effects on mineralization of repeated DBU applications were small to negligible. For the latter soil, the effect on mineralization of applied DBU concentrations from 0.0008 to 80 g g^–1 was also investigated. Mineralization rates decreased from 0.43 to 0.019day^–1 with increasing DBU concentrations. However, the amount of DBU mineralized by day 70 was similar across concentrations and averaged 83% of applied. Microbial respiration was not affected by increasing DBU concentrations. These findings support the supposition that DBU is readily degraded by soil microorganisms, thus unlikely to accumulate in agricultural soils.     

Uptake and distribution of cadmium in maize inbred lines

Genotypic variation in uptake and distribution of cadmium (Cd) was studied in 19 inbred lines of maize (Zea mays L.). The inbred lines were grown for 27 days on an in situ Cd-contaminated sandy soil or for 20 days on nutrient solution culture with 10 µg Cd L^-1. The Cd concentrations in the shoots showed large genotypic variation, ranging from 0.9 to 9.9 µg g^-1 dry wt. for the Cd-contaminated soil and from 2.5 to 56.9 µg g^-1 dry wt. for the nutrient solution culture. The inbred lines showed a similar ranking for the Cd concentrations in the shoots for both growth media (r²=0.89). Two main groups of inbreds were distinguished: a group with low shoot, but high root Cd concentrations (shoot: 7.4±5.3 µg g^-1 dry wt.; root: 206.0±71.2 µg g^-1 dry wt.; shoot Cd excluder) and a group with similar shoot and root Cd concentrations (shoot: 54.2±3.4 µg g^-1 dry wt.; root: 75.6±11.2 µg g^-1 dry wt.; non-shoot Cd excluder). The classification of the maize inbred lines and the near equal whole-plant Cd uptake between the two groups demonstrates that internal distribution rather than uptake is causing the genotypic differences in shoot Cd concentration of maize inbred lines. Zinc (Zn), a micronutrient chemically related to Cd, showed an almost similar distribution pattern for all maize inbred lines. The discrepancy in the internal distribution between Cd and Zn emphasizes the specificity of the Cd distribution in maize inbred lines.     

Isolation and characteristics of Thiopedia rosea (neotype)

Four new strains of Thiopedia rosea were isolated in pure culture from blooms of platelet-forming purple sulfur bacteria in the top layers of the anoxic hypolimnia of two freshwater lakes. Individual cells of the new strains as well as of T. rosea strain 4211 were spherical to oval, nonmotile and contained gas vesicles in the central part. The predominant photosynthetic pigments were bacteriochlorophyll a and okenone. All strains were strictly anaerobic and obligately phototrophic. Optimal growth occurred at low light intensities of 100 E · m^-2 s^-1 (tungsten lamp); intensities above 150 E · m^-2 s^-1 inhibited growth completely. Photoautotrophic growth was possible at sulfide concentrations up to 0.6 mM; higher concentrations were inhibitory. Acetate, butyrate and valerate supported photoorganotrophic growth in the presence of bicarbonate and sulfide concentrations below 1 mM. Sulfide was required as a source of cellular sulfur because assimilatory sulfate reduction is lacking. All strains were assigned to the species Thiopedia rosea with strain 4211 as a neotype.Dedicated to Prof. Dr. H. G. Schlegel on the occasion of his 66th birthday     

Field metabolic rate and water turnover of the numbat (<Emphasis Type="Italic">Myrmecobius fasciatus</Emphasis>)

The numbat (Myrmecobius fasciatus) is a diurnal and exclusively termitivorous marsupial. This study examines interrelationships between diet, metabolic rate and water turnover for wild, free-living numbats. The numbats (488±20.8 g) remained in mass balance during the study. Their basal metabolic rate (BMR) was 3.6 l CO₂ day^–1, while their field metabolic rate (FMR) was 10.8±1.22 l CO₂ day^–1 (269±30.5 kJ day^–1). The ratio FMR/BMR was 3±0.3 for numbats. We suggest that the most accurate way to predict the FMR of marsupials is from the regression log FMR=0.852 log BMR+0.767; (r²=0.97). The FMR of the numbat was lower than, but not significantly different from, that of a generalised marsupial, both before (76%) and after (62–69%) correction for the significant effect of phylogeny on FMR. However the numbat's FMR is more comparable with that of other arid-habitat Australia marsupials (98–135%), for which the regression relating mass and FMR is significantly lower than for nonarid-habitat marsupials, independent of phylogeny. The field water turnover rate (FWTR) of free-living numbats (84.1 ml H₂O day^–1) was highly correlated with FMR, and was typical (89–98%) of that for an arid-habitat marsupial after phylogenetic correction. The higher than expected water economy index for the numbat (FWTR/FMR=0.3±0.03) suggests that either the numbats were drinking during the study, the water content of their diet was high, or the digestibility of their termite diet was low. Habitat and phylogenetic influences on BMR and FMR appear to have pre-adapted the numbat to a low-energy termitivorous niche.Abbreviations BMR basal metabolic rate - FMR field metabolic rate - EWL evaporative water loss - FWTR field water turnover rate - MR metabolic rate - PVR phylogenetic vector regression - RER respiratory exchange ratio - T_a ambient temperature - T_b body temperature - TBW total body water - CO₂ rate of carbon dioxide production - O₂ rate of oxygen consumption - WEI water economy index - WER water efflux rate - WIR water influx rateCommunicated by I.D. Hume     

Interactions of feeding rates on growth,food conversion and body composition of the freshwater catfish Mystus vittatus (Bloch)

Food intake, growth, conversion efficiency and body composition of the non-air breathing catfish Mystus vittatus (Bloch) were studied in relation to different feeding levels. Fish weighing 817.9 ± 104.00 mg was found to consume a maximum of 156.0 mg live Tubifex worm/g day^-1. Geometrically derived feeding rates of 6.75, 23.00 and 26.00 mg dry food/g live fish day^-1 represent the maintenance, optimum and maximum levels respectively. The SDA increased from 6.75 mg/g day^-1 at maintenance to 13.50 mg/g day^-1 at maximum feeding rate. Starvation brougt about increase in body water content, while there was concomitant decrease in fat and crude protein.     

Artificial feeding and successful reproduction inOrnithodoros moubata moubata (Murray, 1877) (Acarina: Argasidae)

The increasing demand for laboratory-reared argasid and ixodid ticks for research and control purposes makes it necessary to develop effective and standardized tick feeding methods without using live animals as hosts. The in vitro maintenance technique, described in this paper, has been used successfully for rearingOrnithodoros moubata moubata by feeding all nymphal and adult instars through Parafilm^R M sealing film on heparinized bovine blood (fresh standard). The technique is based on a specially designed tick feeding apparatus with a capacity to feed 2000 first nymphal instars (N 1) or up to 200 adults at one time. For different 1-month-old instars feeding rates were between 80–100%. Using this feeding technique the subsequent egg production of female ticks was remarkably high, producing an average of 210.2 eggs per tick with a hatch rate of 96.72%. There was no overall difference in the reproductive capacity of 1-month-old femaleO. m. moubata fed on heparinized and haemolyzed bovine blood (kept deep-frozen), heparinized rat blood and defibrinated ovine blood when compared with those fed on heparinized bovine blood (fresh standard).     

The role of substrate feeding earthworms (Lumbricidae) for bioturbation in a beechwood soil

Summary Burrow formation (burrow length and faeces production) of the substrate feeding earthworm Aporrectodea caliginosa (Savigny) in relation to three temperatures (5, 10 and 15°C) and soil moisture contents (48, 60 and 73% water of dry wt) was determined. Soil moisture content affected the burrowing activity of A. caliginosa only below a distinct threshold (60% water of dry wt). At sufficient moisture an, increase in temperature by 5° C approximately doubled the amount of egesta produced. Another substrate feeding earthworm (Octolasion lacteum (Örley)) showed a similar pattern of burrowing activity.The data for the dependence of the faeces production of A. caliginosa on soil temperature and moisture content were combined with field data. The amount of faeces produced by the population of this earthworm species in a beechwood on limestone was calculated to be about 4.23 kg ha^-1 a^-1. The amount of egesta produced by all substrate feeding species is assumed to exceed 6 kg ha^-1 a^-1, which is equivalent to a soil layer of approximately 9 mm. This group of earthworms is therefore considered to be of greater importance for bioturbation and the formation of mull than previously assumed.     

Contrasts in energy intake and expenditure in sit-and-wait and widely foraging lizards

Summary Daily energy metabolism and water flux were measured with doubly labeled water in the free-living insectivorous lizards Cnemidophorus tigris (mean body mass 15.7 g) and Callisaurus draconoides (8.6 g) in June 1979 in the Colorado Desert of California. C. tigris was an active forager; it spent 91% of its 5-h daily activity period in movement. C. draconoides was a sit-and-wait predator; it spent less than 2% of its 10-h activity period in movement. C. tigris had significantly higher rates of field energy metabolism and water influx (210 Jg^-1 day^-1, 36.8 ul H₂O g^-1 day^-1, N=19) than C. draconoides (136, 17.1, N=18). There were no significant differences between the sexes within either species.The extra costs of free existence were calculated from differences between field metabolic rates and maintenance costs estimated from laboratory respirometry. Rates of energy metabolism during the field activity period were about 1.5x resting levels at 40° C (field active body temperature) for C. draconoides and 3.3 x resting levels at 40° C (field active body temperature) for the more active C. tigris. Feeding rates calculated from water influx data were 13.3 mg g^-1 day^-1 for C. tigris and 5.8 mg g^-1 day^-1 for C. draconoides. Though C. tigris had a high rate of energy expenditure, its foraging efficiency was higher than C. draconoides'.     

Increased taxane accumulation in callus cultures of Taxus cuspidata and Taxus × media by some elicitors and precursors

In Taxus cuspidata callus, vanadyl sulfate (10 mg l^–1) induced a high (146 g g^–1 dry wt) production of 10-deacetylbaccatin III in comparison to 7 g g^–1 dry wt of the control. The content of paclitaxel in this species increased from 16 g g^–1 to 74 g g^–1 dry wt when 20 mg phenylalanine l^–1 was used. In T. media, p-aminobenzoic acid induced the highest content of 10-deacetylbaccatin III (481 g g^–1 dry wt) versus 181 g g^–1 in the control. Paclitaxel increased from 89 to 139 g g^–1 dry wt after adding chitosan (20 mg l^–1) to the cultures.     

The influence of earthworms (Lumbricidae) on the nitrogen dynamics in the soil litter system of a deciduous forest

Summary The influence of earthworms (Aporrectodea caliginosa (Savigny) and Lumbricus castaneus (Savigny)) on the rate of nitrogen net mineralization of the soil was studied in the laboratory and in the field. The additional mineralization of nitrogen cause by the burrowing activity of the substrat feeding earthworm A. caliginosa (N _L )was directly correlated to the biomass of the lumbricids independently of their number. A rise in temperature caused an exponential increase in N _L values. The Q ₁₀ value of this process (2.18) was found to be much higher than that of the nitrogen mineralization without earthworms (Q ₁₀=1.22). At 15°C the N _L value caused by A. caliginosa was calculated to be about 250 g N g^-1 fresh body wt d^-1. Using the experimentally determined exponential relationship between temperature and N _L values, the additional nitrogen mineralization caused by a population of A. caliginosa in a beechwood on limestone was calculated to be 4.23 kg ha^-1 a^-1.In contrast to A. caliginosa the litter dwelling species L. castaneus lost considerable amounts of biomass (56%) during the 4 week incubation period. Only 1/3 of the nitrogen equivalent to the weight loss of the animals was recovered in the mineral nitrogen pool.The addition of litter (old beech leaf litter, freshly fallen beech and ash leaf litter) had a pronounced effect on both nitrogen net mineralization and N _L values of the soil. Presence of old beech leaves caused an increase in both values, wheres the other litter types effected a decrease in nitrogen net mineralization. Fragmented ash litter was found to have the most distinct effect on N _L values (-69%) and nitrogen net mineralization (-74%).     

Chlorobenzoate-Degrading Bacteria in Similar Pristine Soils Exhibit Different Community Structures and Population Dynamics in Response to Anthropogenic 2-, 3-, and 4-Chlorobenzoate Levels

A study was conducted to determine the diversity of 2-, 3-, and 4-chlorobenzoate (CB) degraders in two pristine soils with similar physical and chemical characteristics. Surface soils were collected from forested sites and amended with 500 g of 2-, 3-, or 4-CB g^–1 soil. The CB levels and degrader numbers were monitored throughout the study. Degraders were isolated, grouped by DNA fingerprints, identified via 16S rDNA sequences, and screened for plasmids. The CB genes in selected degraders were isolated and/or sequenced. In the Madera soil, 2-CB and 4-CB degraded within 11 and 42 d, respectively, but 3-CB did not degrade. In contrast, 3-CB and 4-CB degraded in the Oversite soil within 14 and 28 d, respectively, while 2-CB did not degrade. Approximately 10⁷ CFU g^–1 of degraders were detected in the Madera soil with 2-CB, and the Oversite soil with 3- and 4-CB. No degraders were detected in the Madera soil with 4-CB even though the 4-CB degraded. Nearly all of the 2-CB degraders isolated from the Madera soil were identified as a Burkholderia sp. containing chromosomally encoded degradative genes. In contrast, several different 3- and 4-CB degraders were isolated from the Oversite soil, and their populations changed as CB degradation progressed. Most of these 3-CB degraders were identified as Burkholderia spp. while the majority of 4-CB degraders were identified as Bradyrhizobium spp. Several of the 3-CB degraders contained the degradative genes on large plasmids, and there was variation between the plasmids in different isolates. When a fresh sample of Madera soil was amended with 50, 100, or 200 g 3-CB g^–1, 3-CB degradation occurred, suggesting that 500 g 3-CB g^–1 was toxic to the degraders. Also, different 3-CB degraders were isolated from the Madera soil at each of the three lower levels of 3-CB. No 2-CB degradation was detected in the Oversite soil even at lower 2-CB levels. These results indicate that the development of 2-, 3-, and 4-CB degrader populations is site-specific and that 2-, 3-, and 4-CB are degraded by different bacterial populations in pristine soils. These results also imply that the microbial ecology of two soils that develop under similar biotic and abiotic environments can be quite different.     

Highly efficlent plant regeneration from mesophyll protoplasts of Indian field cultivars of tomato (Lycopersicon esculentum)

Three Indian cultivars ofL. esculentum were assessed for shoot regeneration from protoplast-derived calli. Consistent yields of viable protoplasts (>9.0×10⁶ g f.wt.^-1) were obtained from leaflets of 14 days old cultured shoots. Protoplast viability (88–94%) and planting efficiency (55–70%) were recorded for the three cultivars. Up to 71% of the protoplast-derived tissues regenerated shoots.Abbreviations BAP 6-benzylaminopurine - 2,4-d 2,4-dichlorophenoxyacetic acid - g f.wt. gram fresh weight - IAA indoleacetic acid - MS Murashige & Skoog (1962) - NAA -naphthaleneacetic acid - Zea zeatin     

Oxygen consumption of Astyanax fasciatus (Characidae,Pisces): a comparison of epigean and hypogean populations

Synopsis The standard and routine oxygen consumptions of Astyanax fasciatus from one surface population (Rio Teapao) and three cave populations (Chica, Micos and Pachon caves: sAnoptichthys jordani, the Micosfish and Anoptichthys antrobius) were determined individually over 24 hours by the use of a flow-through respirometer and polarographic oxygen electrodes. The phylogenetically oldest Pachon fish had a significantly lower standard metabolic rate (0.230 ± 0.036 mg O₂ g^-1 h^-1) than the epigean Teapao fish, the hybrid Chica fish and the phylogenetically younger Micos fish (0.314 ± 0.081 mg O₂g-^-1h^-1, 0.284 ± 0.048 mg O₂g^-1h^-1, 0.277 ± 0.063 mg O₂g^-1h^-1). No significant differences could be determined among the latter three populations. A significant difference in routine metabolic rate existed only between the Pachon fish (0.309 ± 0.0.56 mg O₂g^-1h^-1) and the Teapao fish (0.415 ± 0.071 mg O₂g^-1h^-1). The Chica fish (0.356 ± 0.084 mg O₂g^-1h^-1) and the Micos fish (0.355 ± 0.080 mg O₂ g^-1h^-1) could not be separated from either the Teapao or the Pachon fish, but a decreasing trend from the surface population through the Chica and the Micos to the Pachon population was obvious. During a starvation period of 29 days the metabolic rate of epigean Teapao and hypogean Pachon fish decreased significantly by 32.5% and 34.8% (standard oxygen consumption rate) and 27.5% and 28.2% (routine oxygen consumption rate), respectively. Body mass loss during the starvation period was 16.3% for the Teapao fish and 9.5% for the Pachon fish.     

Growth,graviresponsiveness and abscisic-acid content of Zea mays seedlings treated with Fluridone

Ten-d-old seedlings of Zea mays L. cv. Tx 5855 treated with 1-methyl-3-phenyl-5-(3-[trifluoromethyl]phenyl)-4-(1H)-pyridinone (Fluridone) were analyzed for abscisic acid (ABA) content using high-performance liquid chromatography with an analysis sensitivity of 2.5 ng ABA g^-1 fresh weight (FW). Seedlings were divided into three portions: leaves, detipped roots, and root tips (terminal 1.5 mm). Control plants (water treatment only; no Fluridone) were characterized by the following amounts of ABA: leaves, 0.114±0.024 (standard deviation) g ABA g^-1 FW; detipped roots, 0.260±0.039±g ABA g^-1 FW; root tips, no ABA detected. We did not detect any ABA in tissues of Fluridone-treated plants. Primary roots of treated and untreated seedlings were strongly graviresponsive, with no significant differences between the curvatures or the growth rates of primary roots of Fluridone-treated and control seedlings. These results indicate that 1) Fluridone completely inhibits ABA synthesis, and 2) ABA is not necessary for positive gravitropism by primary roots of Zea mays.Abbreviations ABA abscisic acid - Fluridone 1-methyl-3-phenyl-5-(3-[trifluoromethyl]phenyl)-4-(1H)-pyridinone - FW fresh weight - SD standard deviation     

Production of ajmalicine and ajmaline in hairy root cultures of Rauvolfia micrantha Hook f., a rare and endemic medicinal plant

Hairy roots of Rauvolfia micrantha were induced from hypocotyl explants of 2–3 weeks old aseptic seedlings using Agrobacterium rhizogenes ATCC 15834. Hairy roots grown in half-strength Murashige & Skoog (MS) medium with 0.2 mg indole 3-butyric acid l^–1 and 0.1 mg -naphthaleneacetic acid l^–1 produced more ajmaline (0.01 mg g^–1 dry wt) and ajmalicine (0.006 mg g^–1 dry wt) than roots grown in auxin-free medium. Ajmaline (0.003 mg g^–1 dry wt) and ajmalicine (0.0007 mg g^–1 dry wt) were also produced in normal root cultures. This is the first report of production of ajmaline and ajmalicine in hairy root cultures of Rauvolfia micrantha.     

Enhanced colchicine production in root cultures of Gloriosa superba by direct and indirect precursors of the biosynthetic pathway

Excised root cultures of Gloriosa superba reached 7.5 g dry wt l^–1 and accumulated 240±40 g colchicine g^–1 cell dry wt after 4 weeks growth. While all precursors (except trans-cinnamic acid) enhanced colchicine content of root cultures without adversely affecting root growth, treatment with p-coumaric acid + tyramine (each at 20 mg l^–1) increased colchicine content to 1.9 mg g^–1 cell dry wt.     

Nature of the phytochrome effect on the binding of glycolate oxidase to peroxisomes in vitro

The attachment of glycolate oxidase to the peroxisomal fraction derived from etiolated barley leaves (Hordeum vulgare L. cr. Dvir) is affected by light. The effect of red irradiation is reversed by subsequent far-red irradiation, indicating the involvement of phytochrome. This phytochrome effect is assumed to be related to phytochrome binding. Indeed, prevention by filipin (1.2·10^-6 mol g^-1 f wt) or cholesterol of phytochrome binding to membranes abolishes the effect of light on the interaction between glycolate oxidase and the peroxisomal fraction. Glycolate oxidase binding is affected by addition of quasi-ionophores such as gramicidin and filipin at a concentration of 0.6·10^-3 mol g^-1 f wt. This fact indicates that peroxisome-glycolate oxidase interaction may be affected by membrane potential. Since both ion transport and membrane potential are known to be affected by phytochrome, it is proposed that phytochrome acts in the light-induced modulation of glycolate oxidase attachment as a quasi-ionophore.Abbreviations GO glycolate oxidase - Pr and Pfr phytochrome forms absorbing in red and far-red, respectively - R and F red and far-red irradiation - Cumulative 20 Kp 20,000 g pellet obtained by centrifugation of the crude extract - 1 Kp 1,000 g pellet - 20 Kp 20,000 g pellet, obtained by centrifugation of 1 Kp supernatant - 1 Kp, 20 Kp and cumulative 20 Kp pellets obtained after density centrifugation through a sucrose cushion