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In conventional solution culture where boron (B) is added as boric acid, fluctuating external B supply often produces confounding and ill-defined physiological and biochemical responses in plants, especially when grown at deficient and marginal B supply. Our previous studies proposed the use of the B-specific resin – Amberlite IRA-743 to develop a B-buffered solution culture. The present study aims to evaluate crucial factors determining equilibrium B concentrations in nutrient solution buffered with the B-loaded resin, including the B loading of the resin, pH in the nutrient solution and B removal from the solution. The equilibrium B concentrations in nutrient solution were determined by both the amount of B sorbed by the resin and the solution pH. At pH 6.05±0.05, the relationship between the resin B content and equilibrium B concentration in the nutrient solution is closely described by the equation: Y = 18.8 X1.457 [ where, Y = equilibrium B concentration (μM) in nutrient solution and X = B content of the resin (mg B g−1 moist resin)]. However, at a given resin B content, lowering solution pH from 7 to 4 significantly increased B concentrations in solution through the release of B from the solid phase of the resin beads. The B-loaded resin was capable of maintaining stable B concentrations in the nutrient solutions, ranging from deficient to marginally adequate B concentrations for dicot species. In conclusion, B concentrations ranging from 0.05 to 11 μM, were buffered for 5 days with the resin loaded with 0.004 – 0.691 mg B g−1 moist resin in the nutrient solution. Precise pH control in the nutrient solution is critical for the success of a B-buffered solution culture study.

This paper reports the influence on nutrient uptake of Eucalyptus urophylla seedlings 5 months after inoculation with Glomus and Pisolithus isolates alone or in competition in a nursery. Though concentrations of some mineral elements in roots or tops varied according to different fungal treatments, there was a substantial increase of nutrient amount of all elements in inoculated seedlings. Phosphorus content in inoculated seedlings were 2.67 to 2.88 times of the uninoculated ones. The total content of N, K and B in the inoculated seedlings was respectively 3.58-7.00, 2.65-3.18 and 2.78-3.88 folds of those of the uninoculated ones. The results showed that inoculation with Pisolithus and/or Glomus isolates affected nutrient uptake and their distribution in parts of seedlings. The two fungal isolates also influenced the acid phosphatase activity in roots.

A pot experiment with dual inoculation of ectomycorrhizal and vesicular arbuscular mycorrhizal fungi in sterilized mix soil was undertaken to determine root colonisation and inoculant effects on Eucalyptus urophylla saplings. Successful colonisation of the two inoculated fungi, Glomus and Pisolithus, was observed with high infection rates at 5 months after inoculation. However the colonisation of each fungus on the roots of dual inoculated saplings decreased when comparing to that of individually inoculated ones. This would indicate the competition between the two fungi in the same root system. Inoculation with the two fungi alone or in combination significantly enhanced the growth of saplings. A positive correlation between the total root length of mycorrhizas and the dry weight of seedlings (r 2=0 79,P=0 05)was identified. Results also showed that both fungi could influence nutrient acquisition of eucalypt saplings.

The second part of the results based on a glasshouse experiment. The inoculant effectiveness of 4 VA mycorrhizal fungi and 1 ectomycorrhizal fungus alone or in combination on the growth of Eucalyptus globulus and E. urophylla saplings was reported. There were substantial differences on the growth among treatments (P < 0.005). Large responses of height growth and biomass stimulated by fungal inoculation were observed for both plants during 16-week growing in a sterilized Karrakatta yellow sand. Average heights of inoculated E. globulus and E. urophylla seedlings were respectively increased by up to 28.86% (Laccaria+Scutellospora, LS) and 86.65% (Laccaria+Glomus, LG), compared to those of uninoculated ones at 16 weeks after inoculation. Dry weights of sapling were up to 129.93% (tops) and 119.93% (roots) for E. globulus, 133.34% (tops) and 174.83% (roots) for E. urophylla respectively relative to controls. The growths of both plants were more significantly enhanced by dual inoculation with Laccaria and one of 4 VA mycorrhizal fungi than those inoculated individually. There were strong interactions between fungal colonization and plant growth, which reflected the inoculation efficacy. Ectomycorrhizal fungi had a major impact on root system form-substantially reducing the proportion of fine roots (specific root length), but this did not occur when only VAM fungi were present. The results also revealed that phosphorus level in soils greatly affected the growth of plants and interacted fungal efficacy as well.

This paper represents the first part of the results from a glasshouse experiment designed to compare the competition of ECM and VAM fungi on root colonization and effects on growth of two Eucalyptus species (E. globulus and E. urophylla). One ECM fungus (Laccaria lateritia) and three VAM fungi belonging to genera Glomus, Acaulospora and Scutellospora, along with field soil as well, were used to inoculate Eucalyptus seedlings alone or in combination. Both ECM and VAM fungi colonized and formed mycorrhizal associations on roots of inoculated seedlings, though infective rates of VAM and ECM tips per meter varied according to inoculant fungi and plant ages. There were some regressive interactions for colonization between the two fungi, as a general trend for ECM root colonization levels to increase with time at the expense of VAM colonization was observed during 16 weeks.

Bioassay measurement was used to estimate the inoculum potential of mycorrhizal fungi in intact soils collected from Eucalypt us plantations of varying ages in Western Australia. The results showed that both ectomycorrhizal ( ECM) and vesicular2arbuscular mycorrhizal (VAM) fungi existed in soils from most plantation sites according to two bait plants(clover for VAM and Eucalypt us for ECM) . The levels of ECM or VAM fungal inoculum were considered to be moderate. Analysis of roots sampled from plantations suggest that Eucalypt us stands are more associated with VAM fungi compared to ECM fungi that occupied most fine roots in older stands. Information from the bioassay experiment suggests that there may be a need for the introduction of a wider range of inoculum to assist the establishment of new Eucalypt us plantations in this region. Further work is required on below2ground ECM fungal diversity in these plantations.

Copper (Cu) deficiency in eucalypts is associated with tree deformation and reduced wood production from plantations. Presently, diagnosis of the early stages of Cu deficiency is unreliable as critical tissue Cu concentrations for tree growth have not been defined. Since wood quality is usually impaired in advance of tree growth, a biochemical test for Cu deficiency was sought for three Eucalyptus species commonly used in plantation forestry (E. globulus Labill., E. grandis Hill ex Maiden and E. urophylla Blake). Foliar Cu requirements for catechol oxidase activity were determined in a glasshouse sand culture study with 10 rates of Cu supply (0, 10 -15, 10 -14, 10 -13, 10 -12, 10 -11, 10 -10, 10 -9, 10 -7 and 10 -5 M). In contrast to shoot dry weight, which only responded to Cu supply in E. urophylla, foliar Cu concentration and catechol oxidase activity, in 140-day-old seedlings, increased with the addition of Cu in all species. Stem lignification also responded to Cu supply in parallel to the activity of catechol oxidase. Functional Cu requirements of 2.4, 2.1 and 2.6 mg kg -1 dry weight for catechol oxidase activity in E. globulus, E. grandis and E. urophylla, respectively, were derived from statistical models fitted to the relationship between catechol oxidase activity and Cu concentrations in recently matured leaves.

The species richness of putative ectomycorrhizal (EM) fungi fruiting in blue gum (Eucalyptus globulus Labill.) plantations in Western Australia was investigated in relation to plantation age. Eleven plantations, 1-8 years old, were selected for study and two native Eucalyptus forest sites in the same region were chosen for comparison. Sporocarps of 44 species of putative EM fungi were collected from the 13 sites. Of these, 30 species were found in blue gum plantations. The number of fungal species was highly positively correlated with plantation age and inversely correlated with soil pH. Young plantations (1-5 years) had 2-9 fungal species and were overwhelmingly dominated by species of Laccaria and Scleroderma. In older plantations (6-8 years), the relative abundance of sporocarps of each species within the fungal community decreased, accompanied by an increase in the number of fungal species (12-17 per site). A brief survey of the two native eucalypt forests in this region revealed a much higher number of fungal species than that observed in plantations. In plantations, species of Descolea, Laccaria, Pisolithus and Scleroderma typically fruited in young plantations. Species of epigeous fungi of the genera Boletus, Cortinarius, Hydnum, Inocybe, Lactarius, Paxillus, Russula and hypogeous fungi, including species of Descomyces, Hysterangium and Mesophellia, were found only in older plantations, or in native forests. Some of the fungi that fruit in young plantations are now being evaluated for use in commercial spore inoculation programs to increase the species diversity of EM fungi in exotic eucalypt plantations.

The effects of addition of Eucalyptus globulus leaf litter on carbon and nitrogen mineralization in soils from a pasture and a native forest were evaluated using a long-term laboratory aerobic incubation assay (29 weeks at 20°C) in leaching microlysimeters. The amount of added leaf litter significantly influenced microbial respiration, microbial biomass and N turnover in both the native forest and pasture soils. Cumulative CO2-C respired increased with increasing rate of leaf litter addition when leaf litter was mixed through the soil or placed on the soil surface. These increases were associated with increases in microbial biomass C content. Cumulative net N mineralization declined in all treatments when litter was added and was lowest when leaf litter was mixed with soil. When leaf litter was added in increasing amounts to the soil surface, there was a concomitant increase in microbial biomass N content (r2=0.79, n = 8), indicating that the reduction in net N mineralization was primarily due to immobilization of N in microbial tissues. In contrast, when litter was mixed with soil in increasing amounts, there was a decrease in microbial biomass N in forest soil and an increase in pasture soil. Consequently, changes in the rate of net N mineralization were not well related to changes in microbial biomass N content. It is suggested that this may be due to the greater activity and more rapid turnover of microorganisms where litter was incorporated resulting in more of the immobilized N being partitioned into metabolic products or dead microbial cells. Incorporation of litter may also have enhanced loss N through denitrification.

The growth characteristics and uptake capacities for NO3- and NH4+, as well as activities of nitrogen assimilating-enzymes have been determined in Scleroderma verrucosum. Biomass, grown on agar or liquid MMN media, was higher on nitrate. When S. verrucosum was grown in the presence of equal amounts of ammonium and nitrate, uptake rate for NH4+ was considerably higher than that of NO3-. In addition, it was found that a limitation in ammonium concentration was a prerequisite for nitrate uptake. Nitrate reductase was stimulated when the fungus was transferred from ammonium to nitrate containing media, indicating that the enzyme was inducible by nitrate and repressed by ammonium. Glutamine synthetase and NAD-glutamate synthase activities were clearly detected in S. verrucosum, while the NADP-glutamate dehydrogenase was almost undetectable. This is consistent with the view that ammonium assimilation occurs through the GS/GOGAT cycle in S. verrucosum.

This contribution describes a simple, reliable, high throughput, and cost efficient method for the determination of phosphite and phosphate concentrations in plant samples from a range of plant families using high performance ion chromatography (HPIC). This protocol is a marked improvement over existing methodologies in terms of the practicalities of sample preparation and reliability of subsequent analysis.

P. cinnamomi is a major pathogen in native plants of Southwestern Australia. The fungicide phosphite decreases the growth of P. cinnamomi in a range of jarrah (Eucalyptus marginata) forest species. One of the main modes of spread of P. cinnamomi in the jarrah forest is via production of zoospores from infected plants and soil. P. cinnamomi sporangia production is approximately 3.5 times more sensitive to phosphite than mycelial growth in vitro. In planta, sporangia and zoospore production is decreased but not prevented if plants in the glasshouse are infected and sprayed with phosphite. The aim of this experiment was to determine whether phosphite prevents the production of zoospores from P. cinnamomi colonised jarrah in the field. It also examined whether zoospores produced from P. cinnamomi growing in phosphite treated plants were able to infect plant tissue

Phosphite has been successfully used to control Oomycete diseases in a range of horticultural and ornamental crops. In Western Australia, aerial applications of phosphite have been used to protect large areas of native bushland from the devastating soil-borne plant pathogen Phytophthora cinnamomi. However, the effects of phosphite on beneficial microorganisms, such as mycorrhiza, has not been studied in natural ecosystems. In horticultural and agricultural studies, results are contradictory. Phosphite significantly increased vesicular-arbuscular fungi (VAM) in leek, whi1e in maize, it decreased the colonisation of roots and the percentage of onion root length infected. This study investigated the effect of phosphite treatments on three species of early colonising ectomycorrhiza fungi (Laccaria, Pisolithus and Descolea) with Agonis flexuosa, Eucalyptus marginata and E. globulus.

Research in plant pathology often relies on testing interactions between a fungicide and a pathogen in vitro and extrapolating from these results what may happen in planta. Likewise, results from glasshouse experiments are used to estimate what will happen if the fungicide is applied in the field. However, it is difficult to obtain conditions in vitro and in the glasshouse which reflect the conditions where the fungicide may eventually be used, in the field. The aim of this paper is to compare results of the effect of phosphite on P. cinnamomi isolates in vitro and in planta.

Phytophthora cinnamomi isolates vary in their sensitivity to phosphite. In vitro studies of the Murdoch Phytophthora collection have identified phosphite tolerant and sensitive isolates (I). The in vitro work of Griffith et al. (1993) found that phosphite sensitive Phytophthora palmivora isolates were inhibited at all phosphate concentrations, whereas tolerant isolates were only inhibited when phosphate was limiting. The aim of the current study was to investigate the interaction of phosphate and phosphite in planta. The ability of these two isolates to colonise Banksia grandis stems at four levels of phosphate, sprayed with 0 and 0.5% was assessed.

Dissoconium is an anamorph genus associated with the teleomorph taxon Mycosphaerella. In Australia, Mycosphaerella species cause significant levels of disease in eucalypt plantations. A recent collection of diseased leaf material from eucalypt plantations in Queensland (Qld) revealed the existence of a Mycosphaerella species, with a Dissoconium anamorph, previously not recorded in Australia.

Effects of chromium (Cr2+) (0-100 000 μmol Cr l-1 MMN agar, supplied as CrO3) and nickel (Ni2+) (0-100 000 μmol Ni l-1 MMN agar, supplied as NiCl2) cations on growth of the ectomycorrhizal fungus Pisolithus, collected from under eucalypts growing in Western Australia, the Philippines and New Caledonia were studied in vivo. The effects of these heavy metals on mycorrhizal formation with Eucalyptus urophylla S.T. Blake were also examined in vitro. Nickel was more toxic to fungal growth and ectomycorrhiza formation than Cr. Substrate levels of Ni greater than 20 μmol l-1 agar and Cr levels greater than 200 μmol l-1 agar decreased mycelial dry weights except for the Australian isolate where mycelial dry weight at harvest was not affected by Cr. Nickel and Cr rates greater than 200 and 2000 μmol l-1, respectively, prevented fungal growth. The fungi differed in their tolerance to the heavy metals and isolates from the Philippines and New Caledonia grew at higher Ni levels than the Australian isolate. Media concentrations of 1000 μmol Cr l-1 and 80 μmol Ni l-1 reduced the percentage of root tips colonized by the fungi. Inoculation with the New Caledonian isolate prevented the appearance of foliar toxicity symptoms in seedlings grown at 80 μmol Ni l-1 agar. The effects of three rates of Ni (0, 30 and 60 μmol Ni kg-1 soil) on the formation of ectomycorrhizas and growth of E. urophylla seedlings in a yellow sand were examined in a glasshouse. The application of Ni reduced the percentage of root tips colonized at week 4, from 12% in the nil treatment to 3% at 60 μmol Ni kg-1 soil, but there was no effect at week 12. The New Caledonian isolate produced the greatest percentage of ectomycorrhizas in all Ni levels (85% at 0, 81% at 30 and 75% at 60 μmol Ni kg-1 soil) and was the only isolate that promoted an increase (5 times the uninoculated treatment) in seedling total biomass at 60 μmol kg-1 soil. Hence, the isolate from a heavy metal-contaminated site not only colonized a grea

The development of ectomycorrhizas on inoculated eucalypt seedlings in commercial nurseries is often slow so that only a small percentage of roots are mycorrhizal at the time of outplanting. If mycorrhizal formation could be enhanced by co-inoculation with bacteria which promote rapid root colonisation by specific ectomycorrhizal fungi, as demonstrated by certain bacteria in the Douglas fir-Laccaria bicolor association, this would be of advantage to the eucalypt forest industry. Two bacterial isolates with a demonstrated Mycorrhization Helper Bacteria (MHB) effect on ectomycorrhiza formation between Pseudotsuga menziesii and Laccaria bicolor (S238), and seven Western Australian bacterial isolates from Laccaria fraterna sporocarps or ectomycorrhizas were tested in isolation for their effect on ectomycorrhizal development by three Laccaria spp. with Eucalyptus diversicolor seedlings. Mycorrhizal formation by L. fraterna (E710) as measured by percentage infected root tips, increased significantly (p < 0.05) by up to 296% in treatments coinoculated with MHB isolates from France (Pseudomonas fluorescens Bbc6 or Bacillus subtilis MB3), or indigenous isolates (Bacillus sp. Elf28 or a pseudomonad Elf29). In treatments coinoculated with L. laccata (E766) and the MHB isolate P. fluorescens (Bbc6) mycorrhizal development was significantly inhibited (p < 0.05). A significant Plant Growth Promoting Rhizobacteria (PGPR) effect was observed where the mean shoot d.w. of seedlings inoculated only with an unidentified bacterium (Elf21), was 49% greater than the mean of uninoculated controls (-fungus, -bacterium). Mean shoot d.w. of seedlings coinoculated with L, bicolor (S-238), which did not form ectomycorrhizas with E. diversicolor, and an unidentified bacterium (Slf14) or Bacillus sp. (Elf28) were significantly higher than uninoculated seedlings or seedlings inoculated with L. bicolor (S-238) alone. This is the first time that an MHB effect has been demonstrated in a eucalypt-ecto

Although pines have been established in plantations in Western Australia for over 100 years, knowledge of the ectomycorrhizal fungal flora is incomplete, or lies in unpublished reports. A survey of ectomycorrhizal fungi associated with Pinus spp. was conducted throughout south-western Australia. Compared with other regions in the Southern Hemisphere where pines have been introduced, the ectomycorrhizal flora of pines in Western Australia is particularly depauperate, with only nine species of fungi identified from sporocarps and a further two taxa identified from mycorrhizas. Species identified from sporocarps (Hebeloma crustuliniforme, Lactarius deliciosus, Paxillus involutus, Rhizopogon luteolus, R. roseolus, R. vulgaris, Suillus luteus, S. granulatus, Thelephora terrestris) and Cenococcum geophilum are a subset of a larger pine mycorrhizal flora found in eastern Australia, and 8 of the 10 identified species are common to all regions in the Southern Hemisphere where pines have been introduced. These fungi are typically associated with trees, including pines, in the Northern Hemisphere and, apart from Cenococcum geophilum and T. terrestris, are not associated with indigenous vegetation in Western Australia. The mycorrhizal flora colonising roots in a plantation of Pinus radiata D. Don was also investigated, and compared with species identified as present by above-ground sporocarp production. Potential reasons for the limited ectomycorrhizal flora of pines in Western Australia are discussed.

Rates of microbial respiration and net N mineralization were measured in soils from Eucalyptus globulus Labill. plantations established on ex-pasture and ex-native forest sites using a long-term laboratory aerobic incubation (226 d at 20°C) in leaching microlysimeters. The plantations had been fertilized with either N or P, or both N and P 15 mo prior to soil sampling. Carbon and net N mineralization rates in soils from plantation sites were compared with rates from adjacent pasture and forest sites. Potentially mineralizable N (N0) and net mineralization rate constant (k) were determined using a first-order kinetic model. Application of nutrients to eucalypt plantations significantly influenced net N mineralization processes and the effects differed with previous land use. For both ex-native forest and ex-pasture plantation sites, addition of N fertilizer markedly increased (about 2-fold) k, and reduced N0. Addition of P in the absence of N to the ex-native forest plantation soil reduced cumulative net N mineralization. Both the amount and rate of net N mineralization were associated with previous land use. The proportion of total soil N mineralized during incubation was similar in the ex-native forest plantation, ex-pasture plantation and pasture soils and higher than in the native forest soil. The relative amounts of CO2-C respired per unit of net N mineralized differed between the land use units and was greatest on the native forest site, reflecting the high C-to-N ratio of soil organic matter and potential for N immobilization in soil from the native forest relative to the managed ecosystems. Amounts of net N mineralized (kg ha-1 in 0-200 mm soil) during the initial 28 d aerobic incubation declined in the order: pasture (29)>ex-pasture (18)>ex-native forest (14)> native forest (3), reflecting the low net N mineralization in native forest soil compared to managed ecosystems. The reason for the large difference (about 40%) between the amounts of net N mineralized

As many eucalypts in commercial plantations are poorly ectomycorrhizal there is a need to develop inoculation programs for forest nurseries. The use of fungal spores as inoculum is a viable proposition for low technology nurseries currently producing eucalypts for outplanting in developing countries. Forty-three collections of ectomycorrhizal fungi from southwestern Australia and two from China, representing 18 genera, were tested for their effectiveness as spore moculum on Eucalyptus globulus Labill. seedlings. Seven-day-old seedlings were inoculated with 25 mg air-dry spores in a water suspension. Ectomycorrhizal development was assessed in soil cores 65 and 110 days after inoculation. By day 65, about 50% of the treatments had formed ectomycorrhizas. By day 110, inoculated seedlings were generally ectomycorrhizal, but in many cases the percentage of roots colonized was low (< 10%). Species of Laccaria, Hydnangium, Descolea, Descomyces, Scleroderma and Pisolithus formed more ectomycorrhizas than the other fungi. Species of Russula, Boletus, Lactarius and Hysterangium did not form ectomycorrhizas. The dry weights of inoculated seedlings ranged from 90% to 225% of the uninoculated seedlings by day 110. Although plants with extensively colonized roots generally had increased seedling growth, the overall mycorrhizal colonization levels were poorly correlated to seedling growth. Species of Laccaria, Descolea, Scleroderma and Pisolithus are proposed as potential candidate fungi for nursery inoculation programs for eucalypts.

Phytophthora cinnamomi is a major pathogen of native plant communities in Western Australia, where it affects approximately 14% of the northern jarrah (Eucalyptus marginata) forest and over 2000 of the 9000 plant species in the Banksia woodlands and heathlands of the south-west of Western Australia [1]. Mining operations and timber harvesting are major activities in areas where P. cinnamomi is prevalent and its presence increases the financial costs associated with these activities. Hence, the development of a method to contain or eradicate the fungus will be a great financial advantage to mining companies. Fungicides have rarely been used to control diseases in native plant communities due to high cost and phytotoxic responses. However, recent research has shown that neutralized phosphorous acid (phosphite) has value in conserving rare and endangered plant species in the south-west of Western Australia. This work examines the long-term efficacy of phosphite to control P. cinnamomi in a number of plant species when applied to foliar run-off over different seasons.

Fast growing species of eucalypts are widely planted for land stabilization and commercial forestry in east Asia. In southern China, in particular, large areas of eucalypt plantations have been established since the 1980's and these now total about 800,000 ha. Knowledge of nutrient requirements is important for maximizing eucalypt establishment and growth on these infertile and eroded forest lands. Here, micronutrient supply is usually low because of the depletion of organic matter and nutrient-rich surface soil as a result of past climate conditions and utilization practices, as well as the lack of micronutrient inputs to forest lands. Heavy applications of N, P and K fertilisers have been adopted for eucalypt plantations and this can further exacerbate the extent of micronutrient disorders. Generally, the importance of micronutrient application for sustained tree growth has not been recognised by forest farmers. Results of micronutrient application experiments for different locations and soil types are presented. In most experiments, application of micronutrients increased growth and productivity of eucalypt trees. Boron deficiency was a common limiting factor in southern China as well as in the Philippines. On soil over shale in Longchuan, Guangdong Province, mixed micronutrient application increased height growth of Eucalyptus urophylla by 80% and diameter by 17%. The B concentration in the youngest fully expanded leaves (YFEL) of trees fertilized with NPK and micronutrients was much higher than the trees supplied only with NPK. The NPK trees had die-back symptoms in the crown indicative of B deficiency. In a B, Zn, Cu and other micronutrient depletion experiment on the same site, the addition of B + Zn + Mn +Fe+ Mo promoted maximum growth. On soil over granite in Wuhua, Guangdong Province, B application substantially increased the growth and form of E. urophylla. In Chuxiong, Yunnan Province, E. globulus growing in soil derived from sandstone developed apical d

The effectiveness of an isolate of Pisolithus from Australia was compared with a Philippine Pisolithus isolate in promoting the growth of Eucalyptus urophylla on three acid (pH 4.1-5.9, 0.005M CaCl2) sites in the Philippines (Pangasinan, Bukidnon and Surigao). Isolates of Pisolithus were taken from basidiocarps collected under eucalypts growing in Western Australia and from the Philippines. Generally, the introduced Pisolithus promoted greater wood volume of E. urophylla planted in dry marginal land (Pangasinan) and in moist logged-over area (Surigao) in the Philippines than the Philippine Pisolithus isolate. Root colonization by the two fungi did not vary but there was a difference in the root colonization levels between sites implying that the prevailing microclimatic conditions on each site had affected the performance of the ECM inoculants. In this study, the number of isolates tested was limited, thus, future field trials should include a wider range of ectomycorrhizal fungi. Further work is required to determine whether the growth responses measured at the two sites (Pangasinan and Surigao) are maintained until the trees are harvested.

Eucalyptus species are of great importance to plantation forestry and play a significant role in world timber supply. Some 460,000 ha of Eucalyptus plantations have been planted in China, and about 60,000 ha are established each year (Bai & Gan, 1996). However, successful plantations of exotic eucalypts in China may require inoculation of nursery plants with effective mycorrhizal fungi, since the diversity of ectomycorrhizal fungi in eucalypt plantations in southern China is low (Dell & Malajczuk, 1996; Gong et al., 1997). Eucalypt trees form ectomycorrhizas (ECM) and the anatomy, morphology and ecology, as well as physiology of these associations have been extensively studied (Brundrett et al., 1996). Eucalyptus seedlings are capable of forming both ECM and vesicular-arbuscular mycorrhiza (V AM), even on the same root system (Brundrett et al., 1996; Chilvers et al., 1987). Colonization of different fungi in the same root system commonly occurs in nature, but little is known about its significance. Tree seedlings with multiple mycorrhizas including both ECM and V AM fungi may withstand a wider range of site conditions than those colonized by one fungus.

Quantitative relationships between external boron concentrations that could elicit boron deficiency and plant growth, boron uptake rate, and plant boron concentrations have not been previously investigated due to the lack of water culture systems that provide satisfactory control over solution boron concentrations. Two approaches were tested to buffer the boron concentrations in nutrient solutions: supplying different amounts of boron saturated resin Amberlite IRA 743 per unit solution volume; and loading the resin with boron at 1 to 100% of full saturation. Mean boron concentrations (μM) ranged from 0.17 to 2.85 and from 0.047 to 27.03 in the two approaches, respectively, and in individual pots with plants solutions remained constant in boron concentrations for at least 10 to 12 d. At solution boron concentrations from 0.04 to 0.3 μM, canola (Brassica napusL.) plants remained alive, but shoot and root growth was stunted and showed classical boron deficiency symptoms. Increasing solution boron concentrations progressively increased boron concentrations in shoots and roots. Boron concentrations in roots were less than one-third of those in lower shoots, and less than those in upper shoots, except in boron deficient plants. In boron buffered solutions, dry matter of canola at both 12 and 24 d increased with increasing solution boron concentration up to 0.54–0.87 μM. With increasing solution boron concentrations up to 26.5 μMthere was no further increase in dry matter, and no detrimental effects on plant growth. At 0.04 μMboron, plants absorbed no boron from solution. Increasing solution boron concentrations from 0.1 to 26.5 μMincreased relative boron uptake rates from 0.005 to 0.1 μmol g−1root f.wt d−1. Maximum root efficiency, defined as relative uptake rate divided by the solution boron concentration, was achieved at 0.04 to 0.3 μMboron in solution. With increasing solution boron concentrations, relative uptake rates of calcium decreased from 248 to 10 μmol g−1root

This review focuses on physiological responses in higher plants to B deficiency at the whole plant and organ level. Plants respond to decreasing B supply in soil solutions by slowing down or ceasing growth. Boron deficiency inhibits root elongation through limiting cell enlargement and cell division in the growing zone of root tips. In the case of severe B deficiency, the root cap, quiescent centre and protoderm of root tips disappear and root growth ceases, leading to the death of root tips. Although vascular bundles are weakly developed in B-deficient roots, early effects of B deficiency on their initiation and differentiation is poorly understood. Inhibited leaf expansion by low B indirectly decreases the photosynthetic capacity of plants, though exact roles of B in photosynthesis remain to be explored. The early inhibition of root growth, compared to shoot growth, increases the shoot:root ratio. It is hypothesised that this may enhance the susceptibility of plants to environmental stresses such as marginally deficient supplies of other nutrients and water deficit in soil. In the field, sexual reproduction is often more sensitive to low soil B than vegetative growth, and marked seed yield reductions can occur without symptoms being expressed during prior vegetative growth. In flowers, low B reduces male fertility primarily by impairing microsporogenesis and pollen tube growth. Post-fertilisation effects include impaired embryogenesis, resulting in seed abortion or the formation of incomplete or damaged embryos, and malformed fruit. However, there is a great diversity of effects of low B on reproductive growth among species, and within the same species between sites and seasons. Much of this diversity is not explained by the current literature. Key processes in reproductive development which may be impaired under B deficiency are proposed and discussed. These include the formation of a diverse array of cell wall types, the supply of carbohydrates for growth and st

The effect of boron (B) deficiency on reproductive development was examined in a wheat line SW41 at 4 B levels in a field experiment. The soil B levels (designated BO, B1, B2, B3) ranged from 0.1 to 0.2 mg hot water soluble B kg-1. No effect on vegetative growth was detected at any of the B levels, but the number of grains per ear increased with B, from 7 in BO to 21 in B3; and Grain Set Index (GSI) also increased from 22 to 60%. At ear emergence, B content (mg B kg-1 DW) of the ear ranged from 2.2 to 3.1, and of the flag leaf from 4.1 to 4.7, but these bore slight to no relationship to the number of grains per ear or GSI. Higher B concentrations were found in the carpel, and higher still in the anthers. More significantly, grain set was closely correlated with B in the carpel (R2 = 0.86) and anthers (R2 = 0.77). The significant correlation between GSI and carpel and anther B was confirmed with a larger set of data. With 7 mg B kg-1 DW in the anthers and 5 mg B kg-1 DW in the carpel, the number of grains per ear was doubled when cross pollination with B deficiency tolerant Fang 60 growing near by was allowed. In ears with 9 mg B kg-1 in the anthers and 8 mg B kg-1 in the carpel the effect of cross pollination was smaller, but still significant. The critical deficiency concentration (CDC) of B for the anthers was determined at 10 mg B kg-1 and for the carpel at 8 mg B kg-1. Histological examination of SW41 anthers revealed that microsporogenesis in B-deficient plants proceeded normally up to at least the uninucleate, vacuolate stage. However, pollen maturation was severely affected resulting in shrivelled pollen grains. The programmed development of the tapetum and endothecial layers appeared normal in anthers where partial or complete sterility occurred. It is concluded that reproductive development in wheat requires more B than vegetative growth. The B requirement of the male reproductive organ, the anthers, was also greater than that of the carpel. Since the B req

Seeds used to plant a crop may contain sufficient molybdenum (Mo) to prevent subsequent Mo deficiency in the crop even when they are sown on Mo deficient soils. However, little is known about either the sources of the Mo acquired by the seed, or the timing of its redistribution during seed development. A glasshouse experiment was set up to examine the effect of Mo supply and nitrogen source on the redistribution of Mo within black gram, from full flowering to seed maturity. Treatments comprised two sources of N (symbiotic N2fixation, NH4NO3), two levels of Mo supply [nil (−Mo), 0.64 mg Mo kg−1soil (+Mo)] and four harvests (full flowering, early pod setting, late pod filling and seed maturity). The redistribution of Mo in black gram was examined by determining changes over time in the content of Mo in plant parts at each growth stage. Molybdenum supply and the plant growth stage strongly affected the redistribution of Mo to the seed. In −Mo plants reliant on symbiotic N2fixation, Mo redistributed from roots, stems and leaves was the only source of Mo for reproductive development since, from full flowering until maturity, there was no net increase in whole plant Mo. For pod and early seed development, the roots were the major source of Mo in −Mo plants. After late pod filling, nodules replaced roots as the major source of Mo for seed fill in −Mo plants. By contrast, for +Mo plants reliant on symbiotic N2fixation, Mo taken up from the soil after full flowering could have supplied nearly 50% of the seed Mo. The major sources of Mo for seed filling in +Mo plants were middle stem leaves during early podding, and middle stems and pod walls from late podding. Supplying NH4NO3to plants from sowing had little effect on Mo distribution or redistribution in +Mo black gram plants. However, in −Mo plants it accelerated the loss of Mo from middle stems and their leaves compared to nodulated plants.

Chelated-buffered nutrient solutions are used for studies on micronutrient metals but so far no equivalent system exists for boron nutrition studies: the present investigation was initiated with that intention. From a literature review, it was noted that a range of substances form chelates with boron including polyhydric alcohols, sugars and phenolic compounds. However, none apart from hydrofluoric acid formed chelates with formation constants comparable to those of micronutrient metal chelates like diethylenetriaminepentaacetic acid (DTPA). Moreover, most chelating substances had deleterious side effects which reduced their possible use in water culture: many of the compounds are substrates for bacterial growth, some are harmful to handle, and others are toxic to plants or humans. Borosilicate glass; was tested in a laboratory experiment but found to release boron too slowly into solution to maintain constant boron concentration in solution even when very finely ground. Current investigations centre around the use of a boron-specific resin, which strongly complexes H3BO3 on its N-methyl glucamine functional groups. The boron sorption capacity of the resin varied from 2.2 to 5.0 mg B g-1 resin. Boron saturated resin maintained an equilibrium solution boron concentration of 46 ut M when added at the rate of 2 g of resin to 1 L of boron free triple deionised water. Plants grown in complete nutrient solution with boron saturated resin added at 1 g per litre of nutrient solution grew as well as plants grown in conventional nutrient solution containing 9.2 ut M boron and their shoots contained adequate boron concentrations for growth. There was no evidence that the resin had effects on plant growth other than in releasing and equilibrating boron concentration in the nutrient solution.

From previous glasshouse experiments, 12-18 mg B kg-1 dry wt in the youngest fully expanded leaf blade (YFEL) represents the minimum leaf boron (B) requirement for unrestricted leaf blade elongation (LBE) in black gram (Vigna mungo). A field experiment at Chiang Mai, Thailand was undertaken to test the validity of this B concentration range for diagnosis of B deficiency and to examine the possibility of using B concentration in the YFEL during growth for prognosis of seed yield at maturity. Six levels of B fertilizer (0, 0.5, 1, 2, 4 and 8 kg borax ha-1) and basal fertilizers were applied to 6 replicates. The critical B concentration for diagnosis of pod number in the YFEL at the first mature pod was 13-17 mg B kg- I dry wt being within the range established from the glasshouse experiments. Thus, the functional B requirement for LBE, 12-18 mg B kg-I dry wt in the YFEL, can be recommended for diagnosis of B deficiency in black gram. The critical B ranges in the YFEL for prognosis of seed yield were 31 ± 3, 30 ± 4, 15 ± 1, and 9 ± 1 mg B kg-1 dry wt at the first inflorescence, first pod, first full pod and first mature pod, respectively. The unusually low value of 9 ± 1 mg B kg-1 dry wt is attributed to the recovery of B deficient plants as the result of an increase in B uptake following rain after a drought period. Thus, the use of prognostic values of B deficiency can be limited by the probability of rain after sampling. Despite this limitation, critical values for the prognosis of B deficiency can be used as a guide to the possibility of B deficiency depressing final yield.

Winter oilseed rape (Brassica napus L.) is a major crop in the middle and lower Yangtse river basin, China, where boron (B) deficient soils are widespread. Appearance of B deficiency in oilseed rape often coincides with cold weather during its winter growth. To understand effects of cold weather on plant response to low soil B, a field experiment with oilseed rape cv. Zheyouyou 2 grown in a red soil with low B availability was conducted in Zhejiang province, China. Canopy covers made from transparent plastic sheets were used only at night to modify the microclimate during the early reproductive growth between pre-exposure of flower buds and green bud stage. Canopy treatment (T) increased the minimum air temperature inside the cover by up to 1.5°C when the minimum air temperature in the open was below O°C in early February. Covering plants for 15 days in early February strongly increased shoot dry weight at all levels of B supply. That covering plants increased shoot dry weight of B deficient plants without increasing their leaf B concentration suggests that internal B requirements were decreased. However, because later plant responses at maturity gave contradictory responses, it was concluded that further study of low temperature X B interactions need to be done in controlled environments.

Plants of dicotyledonous trees raised in tissue culture initially have many adventitious roots rather than the single tap root produced by a seedling. Little is known about the subsequent development of the root morphology of tissue cultured trees. Root architecture affects both survival after planting in the field and the likelihood of windthrow when trees are taller. The seedling tap root of eucalypts does not normally persist as the dominant root. Several lateral roots develop as sinker roots, grow to equal thickness and penetrate to great depths (Dell et al, 1989).