Effects Of Mycorrhizal Infection Research Articles

Mycorrhizal colonization in bread wheat varieties differing in their response to phosphorus

Arbuscular mycorrhizal fungi (AMF) play an important role in phosphorus (P) nutrition of plants. Varietal differences in AMF infection occur but there is limited information on the importance of these differences to P efficiency in wheat. This work was conducted to determine whether variation in AMF infection could help explain genetic differences in responses to P. Ten wheat varieties that vary in their grain yield response to P were compared at different rates of P in two controlled environment experiments. Plant samples were also collected from a field experiment with two P rates. Significant genetic variation was observed for AMF colonization in all experiments, but these differences were not consistently related to the yield responsiveness to P among the ten varieties. Two varieties, Carazinho and RAC875 that have a low yield response to P, had consistently high root colonization while a P-responsive variety, Wyalkatchem, had low root colonization. Adding P fertilizer reduced AMF colonization and at high P rates negative associations between AMF colonization and seedling growth and P uptake were observed among the varieties. Among some varieties, their grain yield response to P and P efficiency were consistent with their AMF colonization. However, the negative effect of mycorrhizal infection on seedling growth at high soil P suggests AMF colonization may only be a suitable trait for improved P efficiency in farming systems where available P is consistently low.

Effects of mycorrhizal infection and soil phosphorus availability on in vitro and in vivo pollen performance in Lycopersicon esculentum (Solanaceae)

The effects of mycorrhizal infection and soil P availability on in vitro and in vivo pollen performance were studied in two cultivars of tomato (Lycopersicon esculentum). In the first study, plants were grown in a greenhouse under three treatment combinations: nonmycorrhizal, low P (NMPO); nonmycorrhizal, high P (NMP3); and mycorrhizal, low P (MPO). Mycorrhizal infection and high soil P conditions significantly increased in vitro pollen tube growth rates but not percentage of germination. In addition, pollen from NMP3 and MPO plants sired significantly more seeds than pollen from NMPO plants in pollen mixture studies. In the second study, plants were grown initially in a greenhouse under two treatment combinations: NMPO and MPO. After all plants began to flower, they were placed in experimental arrays in the field. Under open pollination, pollen from MPO plants sired significantly more seeds than pollen from NMPO plants. This result was primarily attributed to increased flower production (and thus pollen production) in MPO plants. Thus, mycorrhizal infection and high soil P conditions can increase pollen quality (in vitro and in vivo pollen performance) as well as pollen quantity, thereby enhancing fitness through the male function. Anthocyanin production (used to determine paternity) also affected pollen performance.

Effects of mycorrhizal infection, soil phosphorus availability and fruit production on the male function in two cultivars of Lycopersicon esculentum

AbstractThe effects of mycorrhizal infection, soil P availability and fruit production on the male function of reproduction were examined in two cultivars of tomato (Lycopersicon esculentum Mill.). Tomato plants were grown in a greenhouse under three treatment combinations: non‐mycorrhizal, low P (NMPO); non‐mycorrhizal, high P (NMP3); and mycorrhizal, low P (MPO). In addition, all treatment combinations were grown both with and without fruit. Fruit production decreased final leaf biomass, flower production and in vitro pollen tube growth rates, often reducing the beneficial effects of increased P uptake. Thus, fruit production diverted resources from subsequent vegetative growth, flower production and pollen development. As the growing season progressed, mean pollen production per flower and in vitro germination and tube growth decreased. Mycorrhizal infection and high soil P conditions increased final leaf biomass, flower production, mean pollen production per flower (in one cultivar) and in vitro pollen tube growth rates. Thus, mycorrhizal infection and high soil P conditions increased pollen quantity and quality, thereby enhancing fitness through the male function. Similar trends in these treatments suggested that mycorrhizal effects on the male function were largely the result of improved P acquisition.

The Effect of Mycorrhizal Fungi on the Fate of PCBs in Two Vegetated Systems

ABSTRACT The objective of this study was to investigate the effects of mycorrhizal infection on vegetative uptake of polychlorinated biphenyls. Feltleaf willow (Salix alaxensis) and balsam poplar (Populus balsamifera) were grown in soil spiked with 6 mg/kg 3,3′,4,4′-tetrachlorobiphenyl-(UL-14C). The fungicide Daconil2787® was employed to suppress indigenous mycorrhizal infection. After 100 days of greenhouse incubation in semienclosed phytoreactors, mycorrhizal infection was found to be approximately threefold higher in the untreated willows vs. the fungicide-amended willows. Radio-label uptake was found to correlate most highly with mycorrhizal infection in the willow roots (R = 0.83). Over the same time period, mycorrhizal infection in the poplars was not significantly affected by fungicide addition. In the poplar phytoreactors, radiolabel uptake was most highly correlated with water use (R = 0.70). The overall vegetative radiolabel uptake was low (≈ 1%), but the limited uptake was attributed to soil sorption processes rather than vegetative limitations.

サギソウ青葉系および‘玉竜花’系のプロトコーム期の生育に及ぼすラン菌根菌の影響

サギソウのプロトコーム期の生育に促進効果の認められたラン菌根菌931202A株の生育促進効果を'青葉'系と'玉竜花'系で比較した.'玉竜花'系は4倍体品種であり, 2倍体である'青葉'系に比べてプロトコーム期の生育は旺盛であった.その差異は, 菌根菌がプロトコーム内に感染しやすく, 通道組織の発達も早く, さらにトリポファギーの形成が急激に進行することにあると思われた.サギソウの初期生育を促進する要因としては, 菌の種類や菌株による効果の差異の他に, サギソウの側にある生理的な差異も重要であると思われた.

Effect of Mycorrhizal Infection in the Tolerance of Pinus contorta to Zinc

Effect of Mycorrhizal Infection in the Tolerance of Pinus contorta to Zinc

Effects of mycorrhizal infection on drought tolerance and recovery in safflower and wheat

The influence of arbuscular mycorrhizal fungi on drought tolerance and recovery was studied in safflower (Carthamus tinctorius L.) and wheat (Triticum aestivum L.). Plants were grown with and without the mycorrhizal fungus, Glomus etunicatum Becker & Gerd., in nutrient-amended soil under environmentally-controlled conditions to yield mycorrhizal and nonmycorrhizal with similar leaf areas, root length densities, dry weights, and adequate tissue phosphorus. When drought stress was induced, mycorrhizal infection did not affect changes in leaf water, osmotic or pressure potentials, or osmotic potentials of leaf tissue rehydrated to full turgor in either safflower or wheat. Furthermore, in safflower, infection had little effect on drought tolerance as indicated by the level of leaf necrosis. Mycorrhizal wheat plants, however, had less necrotic leaf tissue than uninfected plants at moderate levels of drought stress (but not at severe levels) probably due to enhanced phosphorus nutrition. To determine the effects of infection on drought recovery, plants were rewatered at a range of soil water potentials from –1 to –4 MPa. We found that although safflower tended to recover more slowly from drought after rewatering than wheat, mycorrhizal infection did not directly affect drought recovery in either plant species. Daily water use after rewatering was reduced and was correlated to the extent that leaves were damaged by drought stress in both plant species, but was not directly influenced by the mycorrhizal status of the plants.

Root exudation and physiological status of a root-colonizing fluorescent pseudomonad in mycorrhizal and non-mycorrhizal pepper (Capsicum annuum L.)

The effect of mycorrhizal infection on root exudation and the survival and physiological status of a bioluminescent fluorescent pseudomonad on the roots of pepper was examined. Pepper plants were grown for 27 days in split-root microcosms with one side mycorrhizal with Glomus deserticola (GD) or Glomus intraradices (GI) while the other side was non-mycorrhizal. Plants with both sides non-mycorrhizal served as controls. The soil was inoculated with a bioluminescent fluorescent pseudomonad (P. fluorescens 2-79RL). This strain emits light in its exponential growth phase, such that the length of the lag phase prior to bioluminescence can be used to assess the physiological status of the bacterium. Mycorrhizal infection had no significant effect on plant growth. The percent root length infected was 8% for GD and 34% for GI. After pulse-labeling of the shoots with 14CO2, quartz filter strips were used to collect 14C labeled root exudates at specific locations on the roots. Compared with the non-mycorrhizal roots, GI decreased 14C labeled root exudation by 78% at the root tip and by 50% at the older root parts. GD had no effect on 14C labeled root exudation. Rhizosphere soil solutions collected with quartz filter strips were analyzed for amino acids and organic acids by GC-MS. The overall pattern of the chromatograms of the rhizosphere soil solution was similar in the non-mycorrhizal and the mycorrhizal roots. The number of peaks detected was higher in the non-mycorrhizal roots than in the mycorrhizal roots. Compared with the non-mycorrhizal plants, GI decreased the population density of P. fluorescens 2-79RL on the roots by one order of magnitude, both on the mycorrhizal and the non-mycorrhizal side. GD decreased the population density by one order of magnitude only on the side where the fungus was present. The physiological status of P. fluorescens 2-79RL on the roots, as measured by the length of the lag phase prior to bioluminescence, decreased significantly from day 3 to day 6 and remained at a similar level thereafter. Mycorrhizal infection had little effect on the physiological status. Compared to the non-mycorrhizal plants, GI increased the physiological status of P. fluorescens 2-79RL only during the first 6 days, while GD had no effect at all. It is concluded that mycorrhizal infection may decrease root exudation and alter the composition of the rhizosphere soil solution, thereby reducing the population density of certain bacterial groups in the rhizosphere.

Effects of mycorrhizal fungi on in vitro nitrogen response of some Dutch indigenous orchid species

The effect of mycorrhizal infection on the response to mineral nitrogen was studied in Orchis morio L., Dactylorhiza praetermissa (Druce) Soó var. junialis (Vermln.) Sengh., Dactylorhiza majalis (Reichb.) Hunt & Summerh., and Dactylorhiza incarnata (L.) Soó, using two strains of Ceratorhiza sp. and two of Epulorhiza repens (Bernard) Moore as mycorrhizal symbionts. Both types of endophyte appeared to be able to stimulate orchid growth at relatively low nitrogen availability in the culture medium. The Ceratorhiza strains decreased nitrogen tolerance of associated orchid protocorms and had pronounced negative effects on the growth and survival of D. majalis and D. incarnata at high concentrations of ammonium nitrate. Such effects did not occur in symbioses involving the Epulorhiza strains. Within orchid species, differences were observed in the extent to which fungal strains stimulated growth. The Ceratorhiza isolates were incompatible with O. morio while the Epulorhiza strains were generally less efficient for Dactylorhiza spp. Key words: orchid mycorrhiza, nitrogen, Dactylorhiza spp., Orchis morio, Ceratorhiza spp., Epulorhiza repens.

The effect of mycorrhizal infection on survival and growth renewal of micropropagated fruit rootstocks

The effect of mycorrhizal infection on survival and growth renewal of micropropagated fruit rootstocks

The effect of mycorrhizal infection on survival and growth renewal of micropropagated fruit rootstocks

Apple, peach and plum rootstocks were inoculated with the arbuscular mycorrhizal fungus Glomus sp. strain A6 on transplanting from in vitro to in vivo culture. The optimal root length for effective infection, assessed in apple rootstock M 25, was 0.1–1.5 cm, corresponding to the beginning of root elongation. When inoculated at this stage, plants showed maximal growth increase and survival. Mycorrhizal infection of the Mr. S. 2/5 rootstock induced earlier growth renewal after transplanting than in the controls. These results confirm previous reports that mycorrhizal inoculation, performed during transplantation from in vitro to in vivo culture, can enhance both the growth and the survival of plants.

Stratégie d'amélioration de la qualité des plants forestiers et des reboisements méditerranéens par utilisation de la mycorhization contrôlée en pépinière

Summary In the mediterranean region, the strong edaphic, climatic and economic constraints lead to the increase of the transplantation crisis of young trees. The use of controlled mycorrhizal infection is one of the means open to reduce the effects of this crisis by improving the quality of the forest trees grown in nursery, and the reforestation. To achieve this objective, a research/development programme was started and preliminary results are presented: screening of mycorrhizal isolates using physiological criteria; controlled mycorrhizal infection including the study of enzymic polymorphism in mycorrhizae as a tool for characterization of these organs; measurement of the effects of mycorrhizal infection on the nutrition of trees in nursery; ecophysiological study of experimental wood lots.

Mycorrhizas and drought resistance of Picea sitchensis (Bong.) Carr.

summarySitka spruce [Picea sitchensis (Bong.) Carr.] seedlings either mycorrhizal with Paxillus involutus (Batsch) Fr. or non–mycorrhizal were either subjected to drought or watered adequately. Stomatal conductance, net photosynthetic rate and water potential were higher in well–watered mycorrhizal plants than in non–mycorrhizal plants, and the effect of mycorrhizal infection on photosynthesis was interpreted as both a stomatal effect and an effect on the photosynthetic apparatus. During the drought treatment the mycorrhizal plants dried out their substrate sooner than the non–mycorrhizal plants, which were smaller, but their stomatal conductance, net photosynthetic rate and shoot water potential were similar to the non–mycorrhizal plants. A correlation between P concentration in the shoot and net photosynthetic rate was shown. The improved performance of the mycorrhizal seedlings was probably due to their better P and K nutrition and their more extensive root systems with mycelial strands.

Mycorrhizas and drought resistance of Picea sitchensis (Bong.) Carr

summaryMycorrhizal [Paxillus involutus (Batsch) Fr.] and non–mycorrhizal Sitka spruce [Picea sitchensis (Bong.) Carr.] seedlings were grown to comparable size and with comparable shoot N, P and K concentrations in a perlite nutrient solution culture. Shoot water potentials of mycorrhizal and non–mycorrhizal seedlings were related to the moisture content of the substrate during a drying cycle. At any given substrate moisture content, mycorrhizal plants had significantly lower water potentials than non–mycorrhizal plants, the difference being about O.l MPa. In a factorial experiment there was no effect of mycorrhizal infection on stomatal conductance or net photosynthetic rate in either well–watered or droughted seedlings.

Regulation of gene expression in ectomycorrhizas

SUMMARYIn an effort to investigate the presence of any ‘symbiosis‐specific’ genes that are expressed specifically during the development of ectomycorrhizas, the polypeptide content of Eucalyptus‐Pisolithus mycorrhizas, uninfected Eucalyptus globulus (Maid et al.) Kirkp. short roots, and free‐living Pisolithus tinctorius Coker & Couch mycelia have been compared. Analysis of the soluble proteins by two dimensional polyacrylamide gel electrophoresis showed that most of the polypeptides observed in mycorrhizas were already synthesized in free‐living mycelia. The effects of mycorrhizal infection on polypeptide accumulation fell into three distinct categories: (i) decreased amounts of a large number of polypeptides, (ii) increased accumulation of a comparatively few polypeptides and, (iii) appearance of ectomycorrhizins (mycorrhiza‐specific polypeptides). Approximately 50% of the fungal polypeptides and more than 80 % of the plant polypeptides resolved on gels disappeared during the development of ectomycorrhizas. Among 520 polypeptides, 10 polypeptides, called ectomycorrhizins, were ectomycorrhiza‐specific in that they were present in ectomycorrhizas, but not in free living mycelia nor in non‐infected roots. The results showed differential accumulation of ectomycorrhizins during mycorrhiza development. These findings demonstrate that protein synthesis is drastically altered in response to the morphological and physiological changes resulting from the establishment of ectomycorrhiza.

Some effects of nitrate versus ammonium nutrition on the nutrient fluxes in Pinus sylvestris seedlings. Effects of mycorrhizal infection

As a result of the high deposition of ammonium compounds in The Netherlands the forest trees are under a severe nitrogen stress. Effects of increasing amounts of ammonium on the major nutrient fluxes by Scots pine seedlings have been studied. In addition, the effect of mycorrhization of the roots has been taken into account. With nitrate-N nutrition only, the seedlings accumulate calcium, magnesium, potassium, and protons. When a low ammonium concentration is present, the seedlings lose their cations. When the medium is depleted of ammonium, a reuptake of the cations occurs. In the presence of a high ammonium concentration (based on field studies) a continuous loss of cations from the roots takes place. The reverse has been found for phosphate uptake. Ammonium stimulates phosphate accumulation. It is shown that ammonium inhibits the unidirectional influx rate of 86Rb, while concurrently stimulating the unidirectional efflux rate. Mycorrhization of the roots has a beneficial effect on the nutrient fluxes. With nitrate-N nutrition mycorrhizal seedlings accumulate more nitrate, calcium, magnesium, and protons than nonmycorrhizal seedlings. With high ammonium-N nutrition mycorrhizal seedlings lose fewer cations than nonmycorrhizal seedlings. In conclusion, the ecological significance of ammonium deposition on forest stands is discussed.

EFFECTS OF MYCORRHIZAL INFECTION ON PLANT GROWTH, NITROGEN AND PHOSPHORUS NUTRITION IN GLASSHOUSE‐GROWN ALLIUM CEPAL.

SUMMARYGrowth and rates of uptake of nitrogen and phosphorus (inflow) in Allium cepa L. were measured in three experiments. Effects of mycorrhizal infection (Glomus mosseae (Nicol. and Gerd.) Gerdemann and Trappe) and N and P fertilization were investigated. The experiments were carried out in a naturally‐lit glasshouse, so that seasonal variations in solar radiation influenced experimental results.In all experiments, a large positive growth response to mycorrhizal infection was observed when soil P was low. However, at high soil P smaller growth responses to infection were observed, as expected. Infection was associated with increased inflow of P, at all levels of soil P, even when non‐mycorrhizal plants grew as well as or better than mycorrhizal plants. Lower P inflow was observed when infection was low and also at low irradiance in both mycorrhizal and non‐mycorrhizal plants. The results show that mycorrhizal fungi increase the rate at which P is absorbed from soil, even under conditions which precluded a positive growth response to infection.In plants grown in spring and summer (two experiments), mycorrhizal infection was also associated with increased N inflow. N inflows in both mycorrhizal and non‐mycorrhizal plants were lower in a third experiment in late winter and mycorrhizal infection had little or no effect on N inflow in this experiment. Increased N supply increased the inflow of N, concentrations of N in plant tissues and plant growth except in plants that were severely P limited, and there was no evidence that mycorrhizal infection alleviated N stress in low N plants.The results are discussed in relation to the environmental factors limiting plant growth, in particular nutrient uptake via and carbohydrate use by the fungal symbiont.

Vesicular-arbuscular mycorrhizae decrease zinc-toxicity to grasses growing in zinc-polluted soil

Vesicular-arbuscular mycorrhizae (VAM) are known to enhance the uptake of heavy metals in the host and could therefore increase the effects of heavy metal pollution on plant populations. The effect of mycorrhizal infection on two grasses occurring in coastal dunes downwind of a blast furnace complex and which are becoming increasingly polluted, was examined. In a 2 × 2 factorial experiment, the effects of VAM and zinc on the growth and mineral nutrition of Festuca rubra and Calamagrostis epigejos was established. It appeared that VAM infection alleviated the negative effect of zinc on growth in both species. Although both zinc and VAM influenced the uptake and translocation of various minerals, differences in mineral concentrations could not explain why a higher biomass is produced by grasses infected with mycorrhiza in zinc-polluted soil.

Effects of vesicular-arbuscular mycorrhizal infection in first, second and third cereal crops

SUMMARYThe effects of inoculation with the vesicular-arbuscular mycorrhizal fungus Olomics mosseae(Nicolson & Gerdemann) Gerdemann and Trappe, fumigation of soil with methyl bromide, and addition of superphosphate (up to 60 kg P/ha) on growth and phosphorus nutrition of spring wheat (Triticum aestivum L. cv. Highbury) were investigated in two experiments (in 1980 and 1981 respectively) on plots that had been fallowed and recently limed.Fumigation severely reduced natural levels of infection, and slightly reduced yield of above-ground dry matter in both years. In 1981 a decrease in grain yield of about 25% was accompanied by an increase in growth of straw. Plants on fumigated plots contained appreciable amounts of bromine in shoot tissue.Inoculation increased and added P decreased infection in all treatments. In 1980 inoculation had little effect on above-ground dry matter, but it increased concentration of P in shoots especially on plots without added P. In 1981 added inoculum increased yield of grain on fumigated plots by about 0·75 t/ha at all levels of added P, but had little effect on non-fumigated plots, though responses in grain production to added P were similar with and without fumigation. Increases in yield resulting from inoculation were generally accompanied by increases in concentration of P in plant tissue.Winter barley was sown on the plots after their use for spring wheat, without further application of the fumigation, inoculation or phosphorus treatments used in those experiments, to determine any residual effects on mycorrhizal infection and on growth. The levels of mycorrhizal infection on non-fumigated, inoculated plots were relatively constant in successive crops, although numbers of propagules of mycorrhizal fungi increased significantly with time for all treatments. Infection levels on fumigated and non-inoculated plots increased in successive crops, so that the relative effects of fumigation and of inoculation declined with time.The effects of inoculation on infection levels persisted for longer than those on yields, suggesting that maximum effects of mycorrhizal infection on growth did not require the maximum levels of infection found in the roots. Harvest yields continued to respond to applied phosphorus even when uniformly high levels of infection had been established, suggesting that the ability of the root system to absorb phosphate was not greatly increased by mycorrhizal infection.

Vesicular-arbuscular mycorrhizae of winter and spring cereals

SUMMARYThe importance of mycorrhizal infection for the growth of wheat and barley sown in winter and spring was assessed in two field experiments. Low temperatures during winter restricted the development of mycorrhizal infection, and calculations of ‘thermal time’ indicated that the percentage of root length infected did not increase when mean temperatures were less than 5 °C. Hence infection was less in the winter-sown crops than in the spring-sown crops at early stages of plant development. However, the effects of mycorrhizal infection on growth were greater in winter-sown than in spring-sown wheat.At all levels of applied phosphorus up to 60 kg P/ha, artificial inoculation with mycorrhizal fungi increased the yields of both cereals at each sowing date by 17–25% after indigenous mycorrhizal fungi had been removed by fumigation, but the effects were smaller on non-fumigated plots. The results confirmed the potential importance of mycorrhizal infection for the growth of cereals.Mycorrhizal infection increased the phosphorus concentration in the plant tissue at very early stages of growth, but the effect generally declined with time.