How appropriate that at the turn of a century that has overseen a second industrial revolution in agriculture, there is an increasing appreciation of the central role played by the mycorrhizal symbiosis, first described in the latter part of the nineteenth century (Frank, 1885). Simply stated, nearly all families of plants form root symbiotic organs, termed mycorrhizas, with soil fungi belonging to all the main phyla, namely Zygomycotina, Ascomycotina, Basidiomycotina and the Fungi Imperfecti (Harley & Harley, 1987). The importance of this symbiosis in controlling plant nutrient status and growth is well established (Smith & Read, 1997), but a report in this issue now provides, long awaited, nitrogen and phosphorus budgets for mycorrhizal trees (Perez-Moreno & Read, pp. 301–309).

Monstera acuminata is a plant with a problem – it attains a large body size, yet has no secondary growth. For many years, observers have noted the differences in architecture between monocots and woody dicots, particularly in terms of overall size and comparisons of tree-like forms. However, very little is known about the functional morphology of smaller-bodied and ecologically significant climbing and hemiepiphytic monocots, of which M. acuminata is one. In its wider context, the diversity of plant growth forms contributes to the complex structure of many terrestrial ecosystems, where herbs, trees, shrubs, vines, lianas, root-climbers, epiphytes and hemiepiphytes may be said to comprise the ‘skeleton’ of the ecosystem (Speck & Rowe, 1999). This is seen readily, for example, in the humid tropics, which arguably possess the highest taxonomic and structural diversity that has ever been formed by plants on earth. In this issue, López-Portillo et al. (pp. 289–299) investigate the development of plant architecture in Monstera, and demonstrate a range of novel hydraulic parameters.

Summary 167

I. INTRODUCTION 168

II. THE IMPACT OF PROTEIN STRUCTURAL INFORMATION ON THE UNDERSTANDING OF THE PRIMARY REACTIONS IN PHOTOSYNTHESIS 169

1. The structure of the purple bacterial reaction centre 170

2. The structure of PSI 172

3. The structure of PSII 173

4. The structure of antenna complexes 176

(a) Light-harvesting complexes from purple photosynthetic bacteria 177

III. DEVELOPING OVEREXPRESSION SYSTEMS FOR THE STUDY OF PLANT PROTEIN 188

1. Expression of heterologous proteins in Escherichia coli 189

2. Protein expression in the methylotrophic yeast Pichia pastoris 189

3. Expression of recombinant protein in insect cells: the baculovirus system 190

IV. CONCLUSIONS 190

This review sets out the case that now is the time for plant science to establish the technologies required for routinely studying the structure and function of plant proteins. The impact that protein structural information can have is illustrated here with reference to photosynthesis. Our understanding of the precise molecular mechanisms of the light-reactions of photosynthesis has been transformed by the combination of high-resolution protein structural data and detailed functional studies. The past few years have been a particularly exciting time to be engaged in basic plant science research. The application of modern techniques of molecular biology has allowed many key questions to be addressed. The stage is now set for an even bigger revolution as the current plant genome sequencing projects are completed. If these advances are going to be fully exploited, plant science must get to grips with studying proteins, not just genes. Reliable methods for the overexpression of proteins in their native state coupled with routine access to structure determination must become the norm rather than the exception. In 1998 there were about 9000 protein structures deposited in the Brookhaven database. Very few of these are plant proteins. This trend will have to be reversed if research in molecular plant science is to fulfil its potential.

The effects of localized zinc (ZnO) and cadmium (CdS) enrichment on the allocation of root biomass, root length and partitioning of current assimilate within root systems of the Zn hyperaccumulator Thlaspi caerulescens were investigated using a rhizobox system. The rhizoboxes contained either homogeneous soil or juxtaposed control and metal-enriched soil. In the heterogeneous treatments the Zn-enriched soil contained 250, 500 or 1000 mg Zn kg−1. The plants consistently allocated c. 70% of their total root biomass and length into the metal-enriched soil. Moreover, 70% of the current assimilate (14C) allocated to the roots was localized in the Zn-enriched soil of the heterogeneous treatments. The concentration of Zn (250–1000 mg kg−1) in the enriched soil had no effect on these patterns of root allocation, nor were there significant effects of the Zn treatments on the total root or shoot biomass of the plants. The positive responses to the localized metal treatments were therefore characterized by a concomitant reduction in root allocation into the control soil. In contrast to T. caerulescens, when grown with juxtaposed control and Zn-enriched soil the non-accumulator Thlaspi arvense showed reduced root allocation into a patch enriched with 500 mg kg−1 Zn. In a further experiment, two populations of T. caerulescens that differ in their abilities to accumulate Cd were grown with juxtaposed control and Cd-enriched soil. The plants from a population that accumulated Cd also showed increased root biomass and root length allocation into the Cd-enriched soil. Plants from the population that did not accumulate Cd showed no such increase. The possibility that T. caerulescens forages for metals, and the precision of its root allocation with respect to localized metal enrichment is highlighted. The significance of these findings for the selection of hyperaccumulator plants for use in the phytoextraction of Zn and Cd from mine spoils (phytomining) and the phytoremediation of heterogeneous contaminated soils are discussed.

The effects of aluminium (Al) on dividing root-tip cells of Triticum turgidum were investigated with tubulin immunolabelling and electron microscopy. Aluminium affects the mechanisms controlling the organization of microtubule (MT) cytoskeleton, as well as tubulin polymerization, and induces the following aberrations in mitotic cells. (1) It delays the MT disassembly during mitosis, resulting in the persistence of preprophase MT bands in the late prophase cells, the presence of prophase spindles in prometaphase cells, and a disturbance in the shortening of kinetochore MT bundles in anaphase cells. (2) It interferes with the self-organization process of MTs into bipolar systems, inhibiting the formation of prophase and metaphase spindles. (3) Aluminium induces the formation of atypical MT arrays, which in the immunofluorescent specimens appear as ring-like tubulin aggregations in the cortical cytoplasm of the preprophase/prophase cells and as endoplasmic tubulin bundles in prophase and metaphase/anaphase cells; abnormal preprophase MT bands are assembled, consisting of atypical cortical and endoplasmic MT bundles, the latter clearly lining the nuclear envelope on the preprophase MT band plane. (4) It disorders the chromosome movements carried out by the mitotic spindle. In addition, after prolonged Al treatments chromatin condensation is inhibited. The outcome is greatly disturbed organization and function of the mitotic apparatus, as well as inhibition of cells from entering mitosis. This study shows that the MT cytoskeleton is a target site of Al toxicity in mitotic root-tip cells of T. turgidum. The possible mechanisms by which Al exerts its toxicity on MT organization and function are discussed.

The enzyme sucrose: sucrose 1-fructosyltransferase was partially purified from barley leaf growth zones. Four steps (ammonium sulphate precipitation and polyethylene glycol precipitation, followed by chromatography on Concanavalin A-sepharose and hydroxylapatite) yielded a 35-fold purification. The resulting preparation of 1-SST which still contained a number of different activities related to fructan metabolism, was subjected to preparative isoelectric focusing, and sections of the gel were analysed individually for 1-SST and related activities, using sucrose and 1-kestose as substrates. This procedure yielded a 196-fold purification and revealed the presence of two isozymes of 1-SST with pI values of 4.93 and 4.99, as determined by analytical isoelectric focusing of the corresponding fractions. Both isozymes produced glucose and 1-kestose when incubated with sucrose. In addition, small amounts of 6-kestose and tetrasaccharides were formed. In particular, one of the two 1-SST isozymes yielded fructose when incubated with 1-kestose, indicating that it also acts as a fructan exohydrolase. The other isozyme exhibited less fructan exohydrolase activity. Nystose was also degraded by the fructan exohydrolase activity but less than 1-kestose, whereas 6-kestose was not a substrate for the enzyme. Incubation of both 1-SSTs with different concentrations of sucrose showed that the enzyme was not saturated even at 500 mM. As for the barley sucrose: fructan 6-fructosyltransferase, both isozymes of 1-SST yielded two polypeptide bands of molecular weight 50 and 22 kDa upon sodium dodecylsulphate polyacrylamide gel electrophoresis, suggesting their close relationship to invertase (composed of two subunits of similar size), as previously reported for other plants.

Interactive effects of elevated atmospheric CO2 and soil N availability on N2 fixation and biomass production were examined using Gliricidia sepium, a tropical leguminous tree species. Our objective was to determine if elevated CO2 alters the inhibitory effects of soil N on N2 fixation, and whether the response of Gliricidia to elevated CO2 was a function of N source originating from either substrate N fertilizer or N2 fixation. We hypothesized that CO2 enrichment would ameliorate the inhibitory effects of N fertilization on seedling nodulation and N2 fixation through increased C partitioning to nodules. Seedlings were grown from seed for 100 d in growth chambers at either 350 or 700 μmol mol−1 CO2. Seedlings were inoculated with Rhizobium spp. and grown either with 0, 1 or 10 mM N fertilizer. The δ15N isotope-dilution technique was used to determine N source partitioning between N2 fixation and inorganic N fertilizer uptake. The addition of 10 mM N fertilizer significantly reduced nodule number and mass, specific nitrogenase activity, the specific rate of N2 fixation, and the proportion of plant N derived from N2 fixation. Elevated CO2, however, strongly ameliorated the inhibitory effects of N fertilization, indicating that increased C availability for nodule activity may partially offset the inhibition of N2 fixation caused by substrate N, as nodule sugar concentrations were stimulated with CO2 enrichment. This study clearly shows that elevated CO2 enhanced plant productivity and net N content of Gliricidia tree seedlings by stimulating N2 fixation. In addition, seedling biomass production was greatly enhanced by elevated CO2, regardless of whether plant N was derived from the substrate or from the atmosphere. We conclude from this study that CO2 enrichment mitigates the inhibitory effects of substrate N on nodule initiation and development and specific N2 fixation, either through increased C allocation to nodule production and activity, or through increased N demand by the plant for biomass production. This experiment with Gliricidia provides evidence for a positive feedback between increased atmospheric CO2 concentrations, C allocation to symbiotic N2-fixing bacteria, and plant C and N accumulation that may occur when N2-fixing plants are grown under conditions where substrate N may typically inhibit N2 fixation.

Root growth and physiological responses to elevated CO2 were investigated for three important Mojave Desert grasses: the C3 perennial Achnatherum hymenoides, the C4 perennial Pleuraphis rigida and the C3 annual Bromus madritensis ssp. rubens. Seeds of each species were grown at ambient (360 μl l−1) or elevated (1000 μl l−1) CO2 in a glasshouse and harvested at three phenological stages: vegetative, anthesis and seed fill. Because P. rigida did not flower during the course of this study, harvests for this species represent three vegetative stages. Primary productivity was increased in both C3 grasses in response to elevated CO2 (40 and 19% for A. hymenoides and B. rubens, respectively), but root biomass increased only in the C3 perennial grass. Neither above-ground nor below-ground biomass of the C4 perennial grass was significantly affected by the CO2 treatment. Elevated CO2 did not significantly affect root surface area for any species. Total plant nitrogen was also not statistically different between CO2 treatments for any species, indicating no enhanced uptake of N under elevated CO2. Physiological uptake capacities for NO3 and NH4 were not affected by the CO2 treatment during the second harvest; measurements were not made for the first harvest. However, at the third harvest uptake capacity was significantly decreased in response to elevated CO2 for at least one N form in each species. NO3 uptake rates were lower in A. hymenoides and P. rigida, and NH4 uptake rates were lower in B. rubens at elevated CO2. Nitrogen uptake on a whole root-system basis (NO3+NH4 uptake capacity × root biomass) was influenced positively by elevated CO2 only for A. hymenoides after anthesis. These results suggest that elevated CO2 may result in a competitive advantage for A. hymenoides relative to species that do not increase root-system N uptake capacity. Root respiration measurements normalized to 20 °C were not significantly affected by the CO2 treatment. However, specific root respiration was significantly correlated with either root C[ratio ]N ratio or root water content when all data per species were included within a simple regression model. The results of this study provide little evidence for up-regulation of root physiology in response to elevated CO2 and indicate that root biomass responses to CO2 are species-specific.

Ice-core records of the concentration of atmospheric CO2 and its stable isotope ratio (δ13Ca) have shown that the global C cycle has not remained in steady-state over the past 11000 yr, implying a possible change in vegetation activity over this period. Here we evaluated the ecophysiological responses of the dwarf willow (Salix herbacea) over the past 9000 yr by measuring the stable carbon isotope composition and stomatal characters of a unique, well dated, high-latitude (68 °N) sub-fossil leaf sequence. After correction for corresponding changes in δ13Ca, a 9000-yr record of variations in the ratio of intercellular (ci) to atmospheric (ca) CO2 concentration was established. Intercellular[ratio ]atmospheric CO2 concentration ratios provide a time-integrated indicator of the set-point of leaf gas exchange, and the historical variations revealed in this record have been interpreted as an impact of environmental changes on leaf gas exchange. The sequence shows a progressive fall in ci/ca 9000–3000 yr BP as well as the climatic effects of the Medieval Warm Period, the Little Ice Age and the post-industrial CO2 rise. Leaf stomatal index (proportion of epidermal cells as stomata), but not stomatal density, was significantly (P<0.01) correlated with Holocene atmospheric CO2 variations. A process-based interpretation of the changes in ci/ca was made using two different coupled photosynthesis-stomatal conductance models. Calculated in this way, S. herbacea photosynthetic rates were relatively stable throughout the Holocene whilst stomatal conductance progressively declined. Both, however, showed the marked effects of the Medieval Warm Period and the Little Ice Age. Overall, the results demonstrate that S. herbacea leaf metabolism, like the global C cycle, has not remained in steady state during the Holocene but has responded to changes in atmospheric CO2 concentration and short-term climatic oscillations.

Fourier Transform laser Raman spectroscopy was used to generate diagnostic spectra for pigments and biodegradative calcium oxalate in situ in two yellow-pigmented species of the lichen genus Acarospora from contrasting sites in the Antarctic and the Mediterranean. This non-intrusive technique was used to identify the photoprotective pigments rhizocarpic acid and β-carotene by their unique Raman spectral fingerprints. The use of low energy near-IR excitation at 1064 nm eliminated interference from autofluorescence of photosynthetic pigments. The insensitivity of the technique to water permitted the use of field-fresh material. The dominant yellow pigment, rhizocarpic acid, gave a diagnostic pattern of corroborative bands at wavenumbers (ν) 1596, 1665, 1620 and 1000 cm−1. It was possible to discriminate between hydration states of calcium oxalate; the monohydrate (whewellite) featured a ν(CO) stretching band at 1493 cm−1 whereas the dihydrate (weddellite) had a contrasting ν(CO) stretching band at 1476 cm−1. Fourier Transform deconvolution and intensity measurements were used to obtain relative quantitative data for rhizocarpic acid by using its ν(CO) and ν(CONH) amide modes, for carotenoid pigment by its ν(C = C) band at 1520 cm−1 and for calcium oxalates by their ν(CO) bands. ν(CO), ν(CONH) and ν(C = C) are the vibrational stretching modes of the carbonyl C = O, protein amide 1 and alkenyl C = C moieties, respectively, in the pigments and metabolic products of the Acarospora lichens. The ability to determine the precise (20 μm spot diameter) spatial distribution of these key functional molecules in field-fresh thallus profiles and variegations has great potential for understanding the survival strategies of lichens, which receive high insolation, including elevated levels of UV-B, under extremes of desiccation and temperature in hot and cold desert habitats.

The extent of vertical migration of 33P in thalli of the heathland lichen Cladonia portentosa was investigated under field conditions. 33P-labelled orthophosphate was introduced into the bottom 25 mm of podetia cut to a length of 50 mm from the apices. The distribution of label was scanned using a molecular imager immediately after incubation, and after growing for 8 wk and 6 months. Differences in the relative distribution of label between podetia harvested at the beginning and the end of the experiment showed that there had been a significant migration of 33P upwards out of the labelled 25 mm stratum towards the apex. This was confirmed by statistically significant changes in the median (md) and the 90 percentile of total relative distribution of 33P label. In a control treatment in which label was introduced into the apical 25 mm of podetia, which were then grown inverted (top down), no upward movement of label was detected. By contrast, a statistically significant reduction in the md of the distribution indicated migration downwards towards the thallus apex. The results are consistent with the hypothesis that P is recycled within podetia of mat-forming lichens, migrating from degrading basal regions upwards to the growing apices following a source–sink relationship.

The hydraulic architecture of the secondary hemiepiphyte Monstera acuminata was examined in native plants from Los Tuxtlas, Veracruz, Mexico, to determine how it compared to better-known growth forms such as trees, shrubs, lianas and primary hemiepiphytes. Monstera acuminata starts its life cycle as a prostrate herb. As it ascends a tree or other vertical support, the stem becomes thicker, produces larger leaves, and may die back from the base upwards until only aerial feeding roots serve to connect the stem to the soil. Unlike the pattern of vessel-size distribution along the stems of woody dicotyledons, M. acuminata has its wider vessels at the top of the stem, decreasing in diameter towards the base. Also peculiar is the fact that Huber values (axis area/distal leaf area) tend to increase exponentially at higher positions within the plant. Based on the hydraulic conductivity (kh) and leaf-specific conductivity (LSC, kh/distal leaf area), the base of the stem potentially acts as a severe hydraulic constriction. This constriction is apparently not limiting, as aerial roots are produced further up the stem. The plants have remarkably strong root pressures, up to 225 kPa, which may contribute to the maintenance of functional vessels by refilling them at night or during periods of very high atmospheric humidity, as in foggy weather and rain. In common with dicotyledonous plants, vessel length, vessel diameter, kh, specific conductivity (ks, kh/axis area) and LSCs were all positively correlated with axis diameter. The features of the hydraulic architecture of M. acuminata may be an evolutionary consequence of an anatomical constraint (lack of vascular cambium and therefore of secondary growth) and the special requirements of the hemiepiphytic growth form.

The ability of the mycorrhizal fungus Paxillus involutus to mobilize nitrogen and phosphorus from discrete patches of beech (Fagus sylvatica), birch (Betula pendula) and pine (Pinus sylvestris) litter collected from the fermentation horizon of three forest soils, and to transfer the nutrients to colonized B. pendula Roth seedlings, was investigated in transparent observation chambers. The mycelium of P. involutus foraged intensively in all three types of litter, leading to a significant decline in their phosphorus contents after 90 d. Over the same period only one of the litter types, beech, showed more than a 10% loss of its N contents. Exploitation of the litter led to invigoration of the vegetative mycelium of the fungus throughout the chambers as well as to significant increases of biomass production and leaf area in seedlings grown in the plus litter (+L) relative to those in minus litter (−L) systems. The yield increases were associated with gains in whole plant tissue content and concentration of P, but in content only in the case of N. Calculations suggest that a major proportion of the phosphorus lost from litter originated in its organic fraction. The possible basis of the discrepancy between values of N loss from litter and gain by the plant is discussed and the extent to which the distinctive pattern of nutrient mobilization is a feature peculiar to this fungus-plant combination is considered. It is concluded that nutrient mobilization from natural organic substrates in the fermentation horizon of forest soils may be a key function of the vegetative mycelium of mycorrhizal systems. The need for experimental analyses of a greater range of fungus-plant partnerships is stressed.

The inter- and intracellular distribution of phosphate in non-mycorrhizal and ectomycorrhizal roots of Pinus sylvestris was analysed by energy-dispersive X-ray spectroscopy after cryofixation, freeze-drying, pressure infiltration with resin and dry cutting of the material. The results show (1) that in non-mycorrhizal roots the distribution of phosphate across the root cross section is relatively homogenous, (2) that the intracellular distribution of phosphate depends on the external supply, and (3) that the phosphate absorption can be increased by a supply of NH4. Under phosphate starvation, the phosphate is mainly localized in the cell cytoplasm, whereas under high external phosphate this element accumulates in the vacuoles of cortical cells. It can be inferred that at low external conditions phosphate is mainly located in the cytoplasm of cells to protect metabolism from deficiency, that phosphate is translocated to the shoot via symplastic and apoplastic pathways, and that especially the vacuolar pool size is regulated by the external phosphate supply. The nutrition of the host plant under phosphate starvation was improved by a mycorrhizal infection with Suillus bovinus. However, this effect might not be the same for all ectomycorrhizal infections and supply conditions. With high external phosphate an ectomycorrhizal infection with S. bovinus had no effect on intracellular phosphate within the roots, the shoot contents of mycorrhizal plants were less than those of non-mycorrhizal seedlings and translocation rate across the mycorrhizal interface appeared to be independent of the availability of phosphate. Intracellular phosphate in fungal cells of mycorrhizal roots was independent of the external supply and seemed to be regulated by the formation of polyphosphates. A supply of (NH4)2HPO4, which led to an increase in cytoplasmic phosphate levels in the hyphae of the Hartig net of the Paxillus involutus mycorrhiza also led to higher phosphate in the plant cell compartments. Therefore, it can be inferred that the translocation of phosphate from fungus to host plant across the mycorrhizal interface is regulated by the phosphate concentration in the cytoplasm of the Hartig net and by the efflux rate into the interfacial apoplast.

The inter- and intracellular distribution of the elements calcium, potassium and sodium in non-mycorrhizal and mycorrhizal roots of Pinus sylvestris dependent on different external nutrient supply conditions was detected by energy-dispersive X-ray microanalysis after cryofixation, freeze-drying and pressure infiltration of the material. In non-mycorrhizal and mycorrhizal roots, calcium was mainly detectable in the apoplastic regions. The levels in vacuoles and cytoplasm were near the limits of detection by X-ray microanalysis. Incubation with high concentrations of potassium and sodium, or mycorrhizal infection with Suillus bovinus and Pisolithus tinctorius reduced the amounts of calcium detectable in the roots, especially in the apoplast of cortical cells. The studies revealed that: potassium is mainly localized in cytoplasm and cell walls; the cytoplasmic content is regulated over a wide range of external potassium concentrations; potassium levels in the inner parts of roots are higher than in the outer parts. Mycorrhizal infection with Suillus bovinus had no effect on the inter- and intracellular distribution of potassium in roots but, if the external supply was low, the potassium content in shoots was reduced. In non-mycorrhizal pine roots and those infected with Paxillus involutus an increase in the sodium content of all cell compartments was observed after treatment with high external concentrations of NaH2PO4. However, an increase in sodium content in mycorrhizas of S. bovinus was not detected. The X-ray microanalytical results are discussed in relation to the apoplastic movement of nutrients in non-mycorrhizal and mycorrhizal fine roots of pine and to the demand for these nutrients in different intracellular compartments.

The apoplasmic permeability of ectomycorrhizal roots of intact Eucalyptus pilularis seedlings infected with Pisolithus tinctorius on aseptic agar plates was examined using the nonbinding fluorochrome 8-hydroxypyrene-1,3,6-trisulphonate and lanthanum ions in conjunction with anhydrous freeze substitution and dry sectioning. Most mycorrhizas formed in the air above the agar surface, and in these the sheath rapidly became nonwettable and impermeable to the fluorochrome but was nevertheless permeable to lanthanum ions. In a few mycorrhizas which developed in contact with the agar the sheath remained permeable to both tracers when fully developed. This increased hydrophobicity of the sheath in mycorrhizas in the air above the agar surface might be explained by deposition of hydrophobins, but nevertheless it still allows an apoplasmic pathway for radial movement of ions. Regardless of their sheath permeation both apoplasmic tracers were always found throughout the Hartig net and were arrested at the Casparian bands and suberin lamellae of the exodermis. It is concluded that the fluorochrome must have moved longitudinally along the Hartig net which is a region of higher permeability than the sheath. Casparian bands in the exodermis of ectomycorrhizal roots have similar properties to those in nonmycorrhizal roots in excluding solutes and their exclusion of lanthanum ions indicates that they are not permeable to ions. The data do not support the concept of a totally sealed apoplasmic exchange compartment, but the differential permeability suggests that the sheath might allow radial transfer of ions but block loss of sugars and organic molecules of similar size.

A mechanistic model was developed, to simulate the main facets of photoinhibition in phytoplankton. Photoinhibition is modelled as a time dependent decrease in the initial slope of a photosynthesis versus irradiance curve, related to D1 (photosystem II reaction centre protein) damage and non-photochemical quenching. The photoinhibition model was incorporated into an existing ammonium-nitrate nutrition interaction model capable of simulating photoacclimation and aspects of nitrogen uptake and utilization. Hence the current model can simulate the effects of irradiance on photosynthesis from sub-saturating to inhibitory photon flux densities, during growth on different nitrogen sources and under nutrient stress. Model output conforms well to experimental data, allowing the extent of photoinhibition to be predicted under a range of nutrient and light regimes. The ability of the model to recreate the afternoon depression of photosynthesis and the enhancement of photosynthesis during fluctuating light suggests that these two processes are related to photoinhibition. The model may be used to predict changes in biomass and/or carbon fixation under a wide range of oceanographic situations, and it may also help to explain the progression to dominance of certain algal species, and bloom formation under defined irradiance and nutrient conditions.

New Phytologist 144 (1999), 195–202

In the October 1999 issue of New Phytologist, we published the research paper entitled ‘Identification and expression analysis of two fungal cDNAs regulated by ectomycorrhiza and fruit body formation’ by Uwe Nehls et al. (New Phytol. (1999) 144, 195–202). Since its publication, the authors have identified an important error in Fig. 4: the labels SC13 and SC25 are in incorrect positions and should be transposed.

We apologise to our readers for this mistake.