Bioconversion of agricultural lignocellulosic wastes through the cultivation of the edible mushrooms Agrocybe aegerita,Volvariella volvacea and Pleurotus spp.

Ten selected wild and commercial strains of Pleurotus ostreatus,Pleurotus eryngii,Pleurotus pulmonarius, Agrocybe aegerita andVolvariella volvacea were cultivated on three agricultural wastes, i.e. wheat straw (WS), cotton waste (CW) and peanut shells (PS). All species demonstrated significantly higher colonization rates on WS and CW than on PS. WS supported faster growth of A. aegerita and Pleurotus spp., whereas V. volvacea performed better on CW. Comparison of growth rates on composted and non-composted WS and CW substrates revealed that in the latter case faster colonization was achieved, particularly for Pleurotus spp. However, one commercial strain of V. volvacea presented higher growth rates when the composted CW medium was used. Furthermore, earliness in the fructification of P. ostreatus, P. pulmonarius and V. volvacea strains was promoted in CW substrates, while WS favoured earliness of P. eryngii and A. aegerita. Similarly, high sporophore yields were obtained by P. ostreatus and P. pulmonarius on both wastes, whereas WS enhanced yield and basidioma size of P. eryngii and A. aegerita strains and CW production of V. volvacea. The substrates cellulose:lignin ratios were found to be positively correlated to mycelial growth rates and to mushroom yield of P. ostreatus and P. pulmonarius; in addition, positive correlation was also detected for carbon:nitrogen ratio and mushroom yield in P. eryngii and A. aegerita and between cellulose content and mushroom yield for V. volvacea strains.     

Structural investigation of a polysaccharide (Fr. I) isolated from the aqueous extract of an edible mushroom, Volvariella diplasia

A water-soluble polysaccharide, (Fr. I) isolated from the aqueous extract of an edible mushroom, Volvariella diplasia, is composed of D-glucose, D-mannose, and D-galactose in a molar ratio 3:1:1. Compositional analysis, methylation analysis, periodate oxidation study, Smith degradation, and NMR studies (1H, 13C, DQF-COSY, TOCSY, NOESY, ROESY, HMQC, and HMBC) revealed the presence of the following repeating unit in the polysaccharide: [FORMULA: SEE TEXT].     

Sources of resistance to downy mildew (<Emphasis Type="Italic">Peronospora parasitica</Emphasis> (Pers. (ex Fr.) Fr.) in Sicilian germplasm of cauliflower and broccoli

Downy mildew (Peronospora parasitica (Pers. ex Fr.) Fr.) is a serious disease of brassicas in several countries. Seedlings are very susceptible to this pathogen and crops require frequent fungicide treatments to reach a good marketable yield. The use of resistant cultivars can be the most economical, reliable and environmental friendly method for managing this disease. In this work 32 Sicilian landraces and 16 commercial cultivars of cauliflower and broccoli (B. oleracea) were screened for downy mildew resistance at the cotyledon stage using one P. parasitica strain from Portugal and one from Sicily (Italy). Seven-day old seedlings were inoculated by deposing a droplet of a spore suspension on the cotyledons, incubated under controlled environment and scored 7 days later using a seven-class scale of interaction phenotype (IP), which took into consideration host response and pathogen sporulation. There were no differences in virulence between the two P. parasitica isolates. Accessions ranged from very susceptible to highly resistant to downy mildew showing a variable number of resistant individuals per accession. Forty accessions were very susceptible to downy mildew and are of no interest as sources of resistance, since most of the seedlings were scored in the most susceptible IP classes. Seven accessions had intermediate resistance and included individuals that expressed some degree of resistance. Accession Cv 90 (Cavolfiore Torino) and Br 63 (Sparaceddu) showed the majority of seedlings in the resistant IP classes and may constitute valuable sources of resistance to downy mildew to be used in breeding programs.     

Induction of the activities of antioxidative enzymes and the levels of malondialdehyde in cucumber seedlings as a consequence of Bemisia tabaci (Hemiptera: Aleyrodidae) infestation

The activities of antioxidative enzymes and the concentration of malondialdehyde were assayed in cucumber leaves (Cucumis sativus L.) 0, 6, 12, 24, 48, 72, and 96 h after the cucumber seedlings were infested by Bemisia tabaci (Gennadius). The results indicated that the activities of antioxidative enzymes were increased after herbivore infestation, including superoxide dismutase (SOD), and peroxidase (POD), and the levels of malondialdehyde (MDA), which is a product of membrane lipid peroxidation in the leaves. The enzymes and MDA showed peaks of different activity levels at 24 and 48 h after the infestation. SOD activity reached the highest peak, 10.4% higher than control, at 24 h, POD activity reached the highest peak, 213.2% higher than control, at 6 h, catalase (CAT) activity was not statistically significant compared with the control, and MDA content reached the highest peak, 59.9% higher than control, at 48 h. The results suggested that the enhanced activities of antioxidative enzymes and MDA content may contribute to bioprotection of cucumber plants against B. tabaci infestation. Handling editor: Henryk Czosnek     

Changes in antioxidant enzyme activity in the fine roots of black poplar (Populus nigra L.) and cottonwood (Populus deltoides Bartr. ex Marsch) in a heavy-metal-polluted environment

The effect of heavy metal deposition onto soil from a copper smelter on lipid peroxidation and antioxidant enzyme activity in the fine roots of two poplars (Populus nigra L. and Populus deltoides Bartr. ex Marsch) was analyzed. The subjects were mature trees growing in real environments. In both analyzed species, heavy metals stimulated the overproduction of free radicals in fine roots (measured as malondialdehyde level), which was directly proportional to advancing senescence. In young fine roots, heavy metals caused a decrease in guaiacol peroxidase activity and presumably disturbed the lignification process. Catalase was highly sensitive to the presence of heavy metals in the soil. In contrast, ascorbate peroxidase and glutathione reductase activities were unaffected by heavy metals. In the case of superoxide dismutase, a clear increase in enzyme activity was observed only in P. nigra under drought conditions, whereas it was inhibited in polluted stands.     

Pine wilt disease as promising causal agent of the mass mortality of Pinus armandii Franch. var. amamiana (Koidz.) Hatusima in the field

The causal agent of the mass mortality of field populations of Pinus armandii Franch. var. amamiana (Koidz.) Hatusima (PAA) was investigated with special respect to the involvement of pine wilt disease. Wood chips, branches and/or increment cores for detecting the pinewood nematode, feeding marks of the vector insect and environmental stress in the past, respectively, were taken from live and dead PAA trees grown in three locations, Yaku-shima and Tanega-shima Islands and a plantation in Kagoshima City, from 1997 to 1998. Five trees died after the spring of 1996 and, of these, four were inhabited by the pinewood nematode. Feeding marks of the vector insects were found on the branches of all dead trees and most of the live trees investigated. These results suggest that the infection of pine wilt disease in PAA trees occurs in the field. Annual ring growth of the sample trees showed neither intervention nor growth reduction, which implies strong environmental stress that may cause mortality in PAA trees.     

Effects of Na2CO3 and NaCl stresses on the antioxidant enzymes of chloroplasts and chlorophyll fluorescence parameters of leaves of Puccinellia tenuiflora (Turcz.) scribn.et Merr.

Antioxidant enzymes in chloroplasts and chlorophyll fluorescence parameters of leaves of Puccinellia tenuiflora (Turcz.) scribn.et Merr. under isotonic Na₂CO₃ and NaCl stresses were studied. Ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities showed a similar increasing trend and then decreased with the decreasing osmotic potential of culture solution, peaking at −4.74 × 10⁵ Pa under NaCl stress and at −3.40 × 10⁵ Pa under Na₂CO₃ stress. APX, glutathione transferase and SOD activities were higher under NaCl stress than those under Na₂CO₃ stress, and higher activities of antioxidant enzymes in chloroplasts were accompanied by lower MDA content under NaCl stress. F _v/F _m, F _v/F _o and F _v′/F _m′ all initially increased and then decreased with the decreasing osmotic potential of culture solution, while Φ _PSII, qNP and HDR showed a constant increase. F _v/F _m, F _v/F _o, Φ _PSII and qNP under NaCl stress were also shown to be higher than those under Na₂CO₃ stress. The present study suggested that acidity played an important role in the hurt toPuccinellia tenuiflora seedlings, which was due to higher activities of antioxidant enzymes, qNP and Φ _PSII, and the Na₂CO₃ resistance to Puccinellia tenuiflora was also supposed to be less than NaCl resistance in present work.     

Differences in response to the toxin sirodesmin PL produced by Phoma lingam (Tode ex fr.) Desm. on protoplasts,cell aggregates and intact plants of resistant and susceptible Brassica accessions

Summary The selective property of sirodesmin PL, a toxin produced by Phoma lingam, was studied on protoplasts, cell aggregates, leaves and roots. Directly after isolation, protoplasts from all the different Brassica accessions were sensitive when treated with toxin in a concentration higher than 1 M. When more differentiated plant tissue. i.e. cell aggregates, leaves or roots, were investigated, insensitivity to the toxin was found in the plant material resistant to P. lingam, while the plant material susceptible to P. lingam was sensitive. The results reveal that a clear correlation between resistance to P. lingam and insensitivity to sirodesmin PL is present, and that the toxin can be used to distinguish resistant plant material from susceptible both in vivo and in vitro.     

Newly isolated bacterial strains belonging to Bacillaceae (Bacillus sp.) and Micrococcaceae accelerate death of the honey bee mite, Varroa destructor (V. jacobsoni), in laboratory assays

Newly isolated bacterial strains belonging to Bacillaceae (Bacillus sp.), Micrococcaceae and three unidentified strains were tested for their pathogenicity against the mite, Varroa destructor. The Bacillus sp. strain and two of the strains belonging to the Micrococcaceae family significantly decreased the time for 50% mortality of the mite population (up to 57%) and hence may be potential control agents. In in vitro bioassay whole cells, extracellular broth and cellular extract of the Bacillus sp. strain effectively killed the mites, suggesting that both endotoxins and exotoxins contributed to the killing.     

Immunochemical properties and localization of lectin from the basidiomycete <Emphasis Type="Italic">Grifola frondosa</Emphasis> (Fr.) S.F. Gray

The complex of immunochemical methods was applied to study the ability of the lectin from the fungus Grifola frondosa (Fr.) S.F. Gray to interact with homologous and non-homologous rabbit and human polyclonal antibodies. The results of immunodot assay with the fragments of proteolytically cleaved antibodies demonstrated the binding of the lectin only with the Fab fragments (antigen-binding center) of homologous antibodies, which is evidence of specific “antigen-antibody” interaction. The revealed interaction of the lectin with non-homologous antibodies (rabbit antibodies to bacterial O-antigens and the commercial preparation of human g-globulin) is most likely accomplished due to the contact of the carbohydrate-binding region of the lectin with the carbohydrate moiety of the antibodies (“lectin-carbohydrate”). Immunofluorescence microscopy with homologous antibodies revealed that lectin was diffusely and unevenly distributed over the surface of the hyphae, forming agglomerates in the region of buckles and young shoots.     

RAPDs as an aid to evaluate the genetic integrity of somatic embryogenesis-derived populations of Picea mariana (Mill.) B.S.P.

Summary The usefulness of random amplified polymorphic DNA (RAPD) in assessing the genetic stability of somatic embryogenesis-derived populations of black spruce [Picea mariana (Mill.) B.S.P.] was evaluated. Three arbitrary 11-mer primers were successfully used to amplify DNA from both in-vivo and in-vitro material. Twenty-five embryogenic cell lines, additional zygotic embryos and megagametophytes from three controlled crosses involving four selected genotypes of black spruce were used for the segregation analysis of RAPD variants. Ten markers were genetically characterized and used to evaluate the genetic stability of somatic embryos derived from three embryogenic cell lines (one cell line per cross, 30 somatic embryos per cell line). No variation was detected within clones. The utilization of RAPD markers both for the assessment of genetic stability of clonal materials and to certify genetic stability throughout the process of somatic embryogenesis is discussed.     

Cladosporium sphaerospermum as a new plant growth-promoting endophyte from the roots of Glycine max (L.) Merr.

Endophytic fungi are plant symbionts that produce a variety of beneficial metabolites for plant growth and protection against herbivory and pathogens. Fourteen fungal samples were isolated from the roots of soybean cultivar Daemangkong and screened on waito-c rice for their plant growth-promoting capacity. Twelve of the fungal isolates promoted plant growth, while two inhibited it. The fungal isolate DK-1-1 induced maximum plant growth in both waito-c rice and soybean. The plant growth promotion capacity of DK-1-1 was higher than the wild type Gibberella fujikuroi. Gibberellin (GA) analysis of culture filtrate of DK-1-1 showed the presence of higher amounts of bioactive GA₃, GA₄, and GA₇ (6.62, 2.1 and 1.26 ng/mL, respectively) along with physiologically inactive GA₅, GA₁₅, GA₁₉, and GA₂₄. Phylogenetic analysis of 18S rDNA sequence identified the fungal isolate as a new strain of Cladosporium sphaerospermum. Gibberellin production and plant growth-promoting ability of genus Cladosporium are reported for the first time in the present study. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Specific binding of a hypersensitive lignification elicitor from Puccinia graminis f. sp. tritici to the plasma membrane from wheat (Triticum aestivum L.)

We have recently reported the isolation and characterization of a glycoprotein (M_r 67 000) from germ-tube walls of Puccinia graminis f. sp. tritici which elicits the cellular hypersensitive lignification response in wheat (G. Kogel et al., 1988, Physiol. Mol. Plant Pathol. 33, 173–185). The present study uses this glycoprotein, referred to as Pgt elicitor, to identify putative elicitor targets in wheat cell membranes. In enzyme-linked immunosorbent assays using anti-Pgt elicitor antibodies, specific binding sites for Pgt elicitor were detected in highly purified plasma-membrane vesicles of wheat (Triticum aestivum L.) primary leaf cells. Binding proved to be independent of the presence or absence in wheat of the Sr5 gene for rust resistance, and also occurred on barley (Hordeum vulgare L.) plasma membrane. The binding sites have an Mr of 30 000 and 33 000, respectively, and binding activity was not lost in the presence of sodium dodecyl sulfate. [¹⁴C]imido-Pgt elicitor was used to determine the apparent K _d value for specific binding, found to be 2.0 M, and the maximum content of binding sites, found to be 250 pmol per mg of plasma-membrane protein. The relevance of the elicitor binding for the outcome of the interaction of P. graminis and wheat is discussed.Abbreviations BSA bovine serum albumin - ELISA enzyme linked immunosorbent assay - IDPase inosine 5-diphosphatase - MPLC medium-pressure liquid chromatography - MF microsomal fraction - Pgt elicitor elicitor of Puccinia graminis f. sp. tritici - SDS sodium dodecyl sulfate - Pre U₃, Pre U₁ pure plasma membrane from wheat cultivar Prelude and plasma membrane contaminated by intracellular membrane, respectively This work was supported by the Deutsche Forschungsgemeinschaft. We wish to thank C. Larsson, Lund, Sweden for his kind support in the preparation of plasma membrane.     

Physiological responses of Uroleucon jaceae (L.) to seasonal changes in the quality of its host plant Centaurea jacea L.: multilevel control of adaptations to the life cycle of the host

Summary Exploiters of short-lived plants have evolved strategies in response to physiological changes that occur during the development of their hosts. The ability to adapt to host quality changes is necessary particularly if the mobility of an animal is poor or risk-constrained. In the plant-aphid system Centaurea jaceae-Uroleucon jaceae, the responses of the aphid to the seasonal changes in its host plant grown in poor and good quality soil were investigated. Coarse- and fine-tuned physiological reactions were observed in discrete aphid generations which were reared on plants grown either in a growth chamber or in a greenhouse. The number of ovarioles and developmental time depended on extrinsic factors (length of photoperiod) not directly related to plant quality. The reproductive investment of the aphids was also independent of their total dry weight. However, within the gonadal system high correlations were found at the embryonic level (e.g. the number of sclerotized embryos or the length of the oldest embryos per ovariole were highly correlated with gonadal dry weight). Aphids which were living on the 4-leaf stage of high-quality host plants showed a significantly higher investment in their gonads than aphids feeding on senescenting hosts. Factor analysis corroborated that aphids reared on poor-quality hosts revealed no grouping of variables measured, whereas those which were reared on high-quality plants showed clustering in respect of somatic (tibia length, dry weight of soma) and gonadal (number of sclerotized and unsclerotized embryos, length of the oldest embryos, ovariole number, gonad dry weight) factors. Three different levels of adaptive response to plant quality are distinguished: individual response to host quality, maternal influences on offspring and response to changes not specific to habitat (photoperiod). These different levels of regulation are thought to enable the aphids to adapt to a host of a given nutritional quality and anticipate deteriorating habitat quality simultaneously. It is concluded that physiological constraints in aphids are only revealed when aphids are exposed to severe nutritional stress for several generations.     

Oscillations of apoplasmic K+ and H+ activities in Desmodium motorium (Houtt.) Merril. pulvini in relation to the membrane potential of motor cells and leaflet movements

The lateral leaflets of Desmodium motorium exhibit rhythmic upward and downward movements with a period in the minute range. Apoplasmic K⁺ and H⁺ activities were monitored in situ in the abaxial part of the pulvini with ion-selective microelectrodes. An extracellular electric potential was recorded simultaneously. The apoplasmic H⁺ activity of all pulvini exhibiting a regular rhythm of the extracellular electric potential oscillated with the same period between about 10 and 20 mM. The apoplasmic K⁺ activity was high when the membrane potential of the motor cells was depolarized (about 36 mV) and the cells were shrunken. In contrast, the apoplasmic K⁺ activity was low in the swollen state of the motor cells, when the membrane potential was hyperpolarized (about -136 mV). The volatile anesthetic enflurane suppressed reversibly the movement of the leaflets. The same treatment also arrested spontaneous oscillations in the apoplasmic K⁺ activity in the pulvinus. The apoplasmic K⁺ activity oscillated roughly in phase with the K⁺ activity between pH 6.6 and 6.0. Application of white light disturbed the rhythm and increased the extracellular pH. Our results indicate that the physiological mechanism that drives the lateral leaflet movements of Desmodium motorium is closely related to the osmotic motors mediating the leaf movements of Mimosa, Samanea and Phaseolus.Abbreviations E_m membrane potential - E_ex extracellular electric potential - H_ex extracellular H⁺ activity - K_ex extracellular K⁺ activity - R_ex extracellular electrical resistance B. Antkowiak was supported by the Stiftung Volkswagenwerk.     

东北天然针阔混交林凋落物磷素空间异质性及其影响因素

以天然云冷杉(Picea jezoensis var.microsperma(Lindl.) W.C.ChengL.K.Fu and Abies nephrolepis(Trautv.) Maxim.)针阔混交林为研究对象,基于4块1 hm~2固定样地林分调查数据和等距离网格布点取样的400个半分解层凋落物样品的养分测定数据,采用地统计学方法,分析凋落物磷浓度、归还量及利用效率的空间格局特征及其影响因素。结果表明:4块样地凋落物磷浓度均值为1.26 g/kg,归还量均值为24.57 kg/hm~2,利用效率均值为841.74,均表现为中等强度变异,具有明显的空间异质性,且同一样地,变异程度呈现出磷归还量磷利用效率磷浓度。凋落物磷浓度、归还量(样地III和IV结构比大于75%,其空间异质性主要由随机效应引起,不适合进行空间插值)和利用效率主要受结构性因素影响,具有较高的空间自相关性。同一样地磷利用效率的空间异质性较磷浓度及归还量低,各样地磷浓度、归还量和利用效率空间自相关范围分别为9.9—40.5 m、11.9—52.9 m和8.1—39.3 m。同一样地磷利用效率的分形维数高于磷浓度,空间格局较磷浓度复杂,磷浓度空间依赖性更强,具有更好的结构性。凋落物磷浓度、归还量(除样地III和IV)和利用效率呈现条带状和斑块状梯度性分布,且磷浓度和利用效率的空间分布格局相似。凋落物磷浓度、归还量和利用效率受到郁闭度、物种数和植物多样性等多种因子的影响。     

Taxonomic position of a Chinese <Emphasis Type="Italic">Pleurotus</Emphasis> “Bai-Ling-Gu”: it belongs to <Emphasis Type="Italic">Pleurotus eryngii</Emphasis> (DC.: Fr.) Quél. and evolved independently in China

The Chinese Bai-Ling-Gu is a mushroom named Pleurotus eryngii var. tuoliensis C.J. Mou. This species has been identified as P. nebrodensis or P. eryngii var. nebrodensis. We examined its taxonomic position by analysis of mating, cultivation, and rDNA sequences, and concluded as follows. (1) Bai-Ling-Gu mated with P. eryngii var. eryngii, and the F₁ and F₂ formed fruit bodies. (2) Bai-Ling-Gu mated with P. eryngii var. ferulae, and the F₁ formed fruit bodies. (3) In the di-mon mating test, P. eryngii var. nebrodensis from Sicily mated with monokaryons of P. eryngii var. eryngii but mated hardly at all with those of Bai-Ling-Gu and P. eryngii var. ferulae. The di-mon mating pattern of Bai-Ling-Gu resembled those of P. eryngii var. ferulae. (4) The partial sequences of rDNA ITS1 and IGS1 from the epitype of P. nebrodensis were identical with those from P. eryngii var. nebrodensis from Sicily but differed from those from Bai-Ling-Gu. (5) The strains of P. eryngii var. eryngii and P. eryngii var. ferulae were in a group, the strains of P. eryngii var. nebrodensis from Sicily were in another group, and the strains of Bai-Ling-Gu were in the other group in both the phylogenetic trees based on the ITS1 and the IGS1 sequences. These results led to the conclusion that Bai-Ling-Gu is a variety of P. eryngii and evolved independently in China. It is satisfactory to identify Bai-Ling-Gu with P. eryngii var. tuoliensis C.J. Mou.     

Take-off capacity as a criterion for quality control in mass-produced predators,Rhizophagus grandis (Col.: Rhizophagidae) for the biocontrol of bark beetles,Dendroctonus micans (Col.: Scolytidae)

Time spent by adult beetles in cold storage at 3–7°C accounted for 81% of the loss of take-off capacity inRhizophagus grandis Gyllenhal in windtunnel experiments. At the age of three weeks, the insects were at their highest take-off capacity at about 80%. This was followed by a steady decrease, 7% of the insects failing to take-off each month. Changes in the fat reserves during cold storage could explain at least partly this reduction of flight capacity although there was no significant difference in fresh weight between insects that were able/unable to take-off. Sex had a significant influence on take-off rates, with an 8.7% higher take-off rate in females. Take-off capacity was further reduced when the insects were mass-produced in cultures using parent beetles submitted to a blend of synthetic oviposition stimulants instead of live prey larvae. Response to synthetic attractants by those insects which took-off, however, was not influenced by cold storage or by the use of synthetic stimulants in the culture medium.

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Résumé Le temps passé en conservation à basse température (3–7°C) depuis la métamorphose est intervenu pour 81% dans la perte de la capacité d'envol chez le coléoptère prédateurRhizophagus grandis Gyll. lors d'expériences en tunnel de vol. A l'age de trois semaines, les insectes sont à leur plus haut niveau d'envol (envol d'environ 80% des insectes). Par la suite, il y a un déclin constant de la capacité d'envol, à raison de 7% des insectes chaque mois. Des changements dans les réserves lipidiques peuvent partiellement expliquer cette réduction, bien qu'il n'y ait pas eu de différence entre le poids frais d'insectes capables de s'envoler et celui d'individus qui en étaient incapables. Le sexe a une influence sur le taux d'envol, avec un taux d'envol significativement plus élevé de 8.7% chez les femelles. La capacité d'envol est encore réduite chez des insectes qui ont été produits dans des élevages de masse où les parents étaient soumis à un mélange de stimuli de ponte de synthèse au lieu d'être mis en présence de larves deD. micans vivantes. Chez les insectes qui prennent leur vol, cependant, la réponse aux attractifs de synthèse est indépendante de l'age ainsi que des conditions d'élevage.

     

Rapid turnover of the D1 reaction-center protein of photosystem II as a protection mechanism against photoinhibition in a moss,Ceratodon purpureus (Hedw.) Brid.

Susceptibility of a moss,Ceratodon purpureus (Hedw.) Brid., to photoinhibition and subsequent recovery of the photochemical efficiency of PSII was studied in the presence and absence of the chloroplast-encoded protein-synthesis inhibitor lincomycin.Ceratodon had a good capacity for repairing the damage to PSII centers induced by strong light. Tolerance against photoinhibition was associated with rapid turnover of the D1 protein, since blocking of D1 protein synthesis more than doubled the photoinhibition rate measured as the decline in the ratio of variable fluorescence to maximal fluorescence (F_v/F_max). Under exposure to strong light in the absence of lincomycin a net loss of D1 protein occurred, indicating that the degradation of damaged D1 protein inCeratodon was rapid and independent of the resynthesis of the polypeptide. The result suggests that synthesis is the limiting factor in the turnover of D1 protein during photoinhibition of the mossCeratodon. The level of initial fluorescence (F_o) correlated with the production of inactive PSII centers depleted of D1 protein. The higher the F_o level, the more severe was the loss of D1 protein seen in the samples during photoinhibition. Restoration of F_v/F_max at recovery light consisted of a fast and slow phase. The recovery of fluorescence yield in the presence of lincomycin, which was added at different times in the recovery, indicated that the chloroplast-encoded protein-synthesis-dependent repair of damaged PSII centers took place during the fast phase of recovery. Pulse-labelling experiments with [³⁵S]methionine supported the conclusion drawn from fluorescence measurements, since the rate of D1 protein synthesis after photoinhibition exceeded that of the control plants during the first hours under recovery conditions.