Growth and mineral nutrition of non- mycorrhizal and mycorrhizal Norway spruce (Picea abies) seedlings grown in semi-hydroponic sand culture I. Growth and mineral nutrient uptake in plants supplied with different forms of nitrogen
TL;DR: The insignificant differences in uptake rates of N, P, K, Ca and Mg between non-mycorrhizal and mycor rhizal plants indicate that at unlimited spatial nutrient availability the contribution of the extramatrical mycelium to nutrient uptake by mycorrhIZal plants was small.
Abstract: Growth, nitrogen uptake and mineral nutrient concentrations in the plant tissues were determined in non-mycorrhizal and mycorrhizal Norway spruce (Picea abies (L.) Karst.) seedlings grown under controlled conditions in a semi-hydroponic culture system with quartz sand as substrate and a percolating nutrient solution. The culture system allowed the determination of nutrient uptake rates in mycorrhizal root systems with an intact extramatrical mycelium. The rate of infection of the roots by the mycorrhizal fungi Pisolithus tinctorius and Laccaria laccata was high but the rate of infection by Paxillus involutus was low. When supplied with ammonium nitrate, the d. wt of the roots and particularly of the shoots was significantly lower in mycorrhizal than in non-mycorrhizal plants. Despite the lower root d. wt, the number of root tips and the root branching ratio (number of root tips per unit root length) were significantly higher in mycorrhizal plants infected with L. laccata and P. tinctorius than in non-mycorrhizal plants. The depletion of ammonium in the external solution was faster than the depletion of nitrate. Nitrate uptake rates increased at ammonium concentrations below 400 μM. The maximal N uptake rates (V max ), calculated after Lineweaver-Burk, were significantly higher for ammonium than for nitrate. The N uptake rates did not differ significantly between non-mycorrhizal and mycorrhizal plants. The concentrations of N, P, K, Ca and Mg tended to be higher in the smaller mycorrhizal than in the larger non-mycorrhizal plants. A significant increase in mineral nutrient concentration in mycorrhizal compared with non-mycorrhizal plants was found only for N concentrations in the needles of mycorrhizal plants infected with P. tinctorius. When they were supplied with ammonium ((NH 4 ) 2 SO 4 ) as source of N, but not when they were supplied with nitrate (KNO 3 ), the d. wt was lower in mycorrhizal plants infected with P. tinctorius than it was in non-mycorrhizal plants. Therefore, N uptake rates were increased in mycorrhizal plants with P. tinctorius only when they were supplied with ammonium but not with nitrate. The insignificant differences in uptake rates of N, P, K, Ca and Mg between non-mycorrhizal and mycorrhizal plants indicate that at unlimited spatial nutrient availability the contribution of the extramatrical mycelium to nutrient uptake by mycorrhizal plants was small. It is suggested that the decreased growth of mycorrhizal plants is due to the demand of the mycorrhizal fungus for photosynthates, i.e. source limitation.
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TL;DR: During the vegetation periods 1994 and 1995, net uptake of nitrate and ammonium by roots of adult spruce and beech trees was studied at a field site exposed to high loads of N and results indicated that uptake rates at temperatures found in the field were low compared with the uptake capacity at optimum temperature.
Abstract: During the vegetation periods 1994 and 1995, net uptake of nitrate and ammonium by roots of adult spruce (Picea abies (L.) Karst) and beech (Fagus sylvatica L.) trees was studied at a field site exposed to high loads of N ('Hoglwald', Germany). In addition, uptake experiments were carried out under controlled conditions with young spruce and beech trees grown at normal N supply. In the field, nitrate was not taken up by the roots of spruce trees in appreciable amounts. This was also true for beech except during September 1995. Apparently, beech trees was capable of taking up nitrate, but the environmental condition prevailing at the field site usually prevented net uptake. Net uptake of ammonium in both tree species showed a seasonal course, with maximum rates in mid summer. Rates of ammonium uptake by both species correlated with soil temperature at the field site. Laboratory experiments on the influence of root temperature on uptake of nitrate indicated that uptake rates at temperatures found in the field were low compared with the uptake capacity at optimum temperature. At temperatures of 10 and 15°C, frequently found in the soil at the field site, net uptake of nitrate by spruce and beech amounted to c. 16% and 11%, respectively, of maximum uptake at 25°C. By contrast, net uptake of ammonium at 10°C reached 73% and 31% of the maximum uptake for spruce and beech trees, respectively. Independent of temperature, rates of nitrate uptake were considerably lower than those of ammonium. In young spruce and beech trees, net uptake of nitrate was significantly inhibited by ammonium at nitrate∶ammonium ratios found in the soil solution at the forest site. Preincubation of roots of both species, with amino acids present in the phloem of adult trees at the field site, led to an increase in the amino acid pool in the roots. For spruce trees a correlation between inhibition of uptake of nitrate and enrichment of the roots with the amino compounds Glu, γ-amino butyric acid (Gaba), Gln, and Asn was observed. In beech trees, enrichment of Asp and Gln in the roots correlated with a decrease in net uptake of nitrate. The results of laboratory experiments on the effects of temperature, the nitrate to ammonium ratio in the nutrient solution, and amino acid enrichment in the roots are discussed with special emphasis on the patterns of net uptake of ammonium and nitrate observed in the field.
305 citations
TL;DR: Two-way N-transfer warrants further investigation with many species and under field conditions, and the lack of convincing data underlines the need for creative, careful experimental manipulations.
Abstract: Mycorthizae play a critical role in nutrient capture from soils. Arbuscular mycorrhizae (AM) and ectomycorrhizae (EM) are the most important mycorrhizae in agricultural and natural ecosystems. AM and EM fungi use inorganic NH4+ and NO3-, and most EM fungi are capable of using organic nitrogen. The heavier stable isotope N-15 is discriminated against during biogeochemical and biochemical processes. Differences in N-15 (atom%) or delta(15)N (parts per thousand) provide nitrogen movement information in an experimental system. A range of 20 to 50% of one-way N-transfer has been observed from legumes to nonlegumes. Mycorrhizal fungal mycelia can extend from one plant's roots to another plant's roots to form common mycorrhizal networks (CMNs). Individual species, genera, even families of plants can be interconnected by CMNs. They are capable of facilitating nutrient uptake and flux. Nutrients such as carbon, nitrogen and phosphorus and other elements may then move via either AM or EM networks from plant to plant. Both N-15 labeling and N-15 natural abundance techniques have been employed to trace N movement between plants interconnected by AM or EM networks. Fine mesh (25similar to45 mum) has been used to separate root systems and allow only hyphal penetration and linkages but no root contact between plants. In many studies, nitrogen from N-2-fixing mycorrhizal plants transferred to non-N-2-fixing mycorrhizal plants (one-way N-transfer). In a few studies, N is also transferred from non-N-2-fixing mycorrhizal plants to N-2-fixing mycorrhizal plants (two-way N-transfer). There is controversy about whether N-transfer is direct through CMNs, or indirect through the soil. The lack of convincing data underlines the need for creative, careful experimental manipulations. Nitrogen is crucial to productivity in most terrestrial ecosystems, and there are potential benefits of management in soil-plant systems to enhance N-transfer. Thus, two-way N-transfer warrants further investigation with many species and under field conditions.
275 citations
Cites background from "Growth and mineral nutrition of non..."
...For mycorrhizal fungi and roots, uptake kinetics of inorganic N were studied by Littke et al. (1984), Jongbloed et al. (1991), Plassard et al. (1994), Eltrop and Marschner (1996), Gessler et al. (1998), and Wallenda et al. (2000)....
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TL;DR: It is proposed that these divergent responses parallel known differences in tolerance and toxicity to NH 4 + amongst these species, and constitute a significant driving force in forest succession, complementing the discrimination against NO 3 - documented in white spruce.
Abstract: Ratios of ammonium (NH 4 +) to nitrate (NO 3 -) in soils are known to increase during forest succession. Using evidence from several previous studies, we hypothesize that a malfunction in NH 4 + transport at the membrane level might limit the persistence of early successional tree species in later seral stages. In those studies, 13 N radiotracing was used to determine unidirectional fluxes and pool sizes of NH 4 + and NO 3 -in seedlings of the late-successional species white spruce (Picea glauca) and in the early successional species Douglas-fir (Pseudotsuga menziesii var. glauca) and trembling aspen (Populus tremuloides). At high external NH 4 +, the two early successional species accumulated excessive NH 4 + in the root cytosol, and exhibited high-velocity, low-efficiency (15% to 22%), membrane fluxes of NH 4 +. In sharp contrast, white spruce had low cytosolic NH 4 + accumulation, and lower-velocity but much higher-efficiency (65%), NH 4 + fluxes. Because these divergent responses parallel known differences in tolerance and toxicity to NH 4 + amongst these species, we propose that they constitute a significant driving force in forest succession, complementing the discrimination against NO 3 - documented in white spruce (Kronzucker et al. 1997).
110 citations
TL;DR: In this paper, the root processes of interest to both field ecologists and modelers including root classification, production, turnover, biomass, resource uptake, and depth distribution are reviewed.
102 citations
Cites background from "Growth and mineral nutrition of non..."
...As has been long 139 appreciated, the extramatrical hyphae of mycorrhizae increases surface area for water and 140 nutrient absorption, with the effect varying by fungal species (Agerer, 2001) and ion mobility 141 (Bolan, 1991; Eltrop and Marschner, 1996)....
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TL;DR: It can be deduced that the species composition of the fungal community will contribute significantly to the functional diversity of a population of mycorrhizal roots.
Abstract: It is well established that ectomycorrhizal fungi can use amino acids as nitrogen and carbon sources, but data on the kinetic properties of amino acid uptake systems of ectomycorrhizal systems are scarce. Using 14C-labelled compounds we have determined the kinetics of uptake of amino acids by excised ectomycorrhizal roots for a range of distinct mycorrhizal types from three tree species, beech, spruce, and pine. All mycorrhizal types examined took up amino acids via high-affinity transport systems (KM values ranging from 19 to 233 mmol m–3). A comparative analysis of kinetic parameters for uptake of amino acids and the ammonium analogue methylammonium showed that ectomycorrhizal roots have similar or even higher affinities (lower KM values) for the amino acids, indicating that absorption of these organic forms of nitrogen (N) can contribute significantly to total N uptake by ectomycorrhizal plants. Analysis of amino acid uptake by ectomycorrhizal roots collected along a European north/south gradient of increasing mineral N pollution from northern Sweden to south Germany revealed no obvious trend in the uptake capabilities for amino acids by ectomycorrhizal roots in relation to the location of the sampling site on this gradient. Rather, the fungal species forming a particular morphotype was the factor determining uptake kinetics. It can therefore be deduced that the species composition of the fungal community will contribute significantly to the functional diversity of a population of mycorrhizal roots.
96 citations
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TL;DR: Basic research, including the quantification of nutrient uptake and transport by fungal hyphae in soil and regulation at the fungal-plant interface, is essential to support the selection and utilization of mycorrhizal fungi on a commercial scale.
Abstract: The role of mycorrhizal fungi in acquisition of mineral nutrients by host plants is examined for three groups of mycorrhizas. These are; the ectomycorrhizas (ECM), the ericoid mycorrhizas (EM), and the vesicular-arbuscular mycorrhizas (VAM). Mycorrhizal infection may affect the mineral nutrition of the host plant directly by enhancing plant growth through nutrient acquisition by the fungus, or indirectly by modifying transpiration rates and the composition of rhizosphere microflora.
1,327 citations
TL;DR: Mycorrhizal plants have been shown to increase the uptake of poorly soluble P sources, such as iron and aluminium phosphate and rock phosphates, however, studies in which the soil P has been labelled with radioactive 32P indicated that both mycor rhizal and non-mycorrhIZal plants utilized the similarly labelled P sources in soil.
Abstract: The beneficial effects of mycorrhizae on plant growth have often been related to the increase in the uptake of immobile nutrients, especially phosphorus (P). In this review the mechanisms for the increase in the uptake of P by mycorrhizae and the sources of soil P for mycorrhizal and non-mycorrhizal plants are examined. Various mechanisms have been suggested for the increase in the uptake of P by mycorrhizal plants. These include: exploration of larger soil volume; faster movement of P into mycorrhizal hyphae; and solubilization of soil phosphorus. Exploration of larger soil volume by mycorrhizal plants is achieved by decreasing the distance that P ions must diffuse to plant roots and by increasing the surface area for absorption. Faster movement of P into mycorrhizal hyphae is achieved by increasing the affinity for P ions and by decreasing the threshold concentration required for absorption of P. Solubilization of soil P is achieved by the release of organic acids and phosphatase enzymes. Mycorrhizal plants have been shown to increase the uptake of poorly soluble P sources, such as iron and aluminium phosphate and rock phosphates. However, studies in which the soil P has been labelled with radioactive 32P indicated that both mycorrhizal and non-mycorrhizal plants utilized the similarly labelled P sources in soil.
1,143 citations
TL;DR: In this article, the root zone temperature, concentrations and uptake rates of non-mycorrhizal roots of 4-year-old Norway spruce under controlled environmental conditions were studied.
Abstract: Relationships between root zone temperature, concentrations and uptake rates of NH
4
+
and NO
3
−
were studied in non-mycorrhizal roots of 4-year-old Norway spruce under controlled environmental conditions. Additionally, in a forest stand NH
4
+
and NO
3
−
uptake rates along the root axis and changes in the rhizosphere pH were measured. In the concentration (Cmin) range of 100–150 μM uptake rates of NH
4
+
were 3–4 times higher than those of NO
3
−
The preference for NH
4
+
uptake was also reflected in the minimum concentration (Cmin) values. Supplying NH4NO3, the rate of NO
3
−
uptake was very low until the NH
4
+
concentrations had fallen below about 100 μM. The shift from NH
4
+
to NO
3
−
uptake was correlated with a corresponding shift from net H+ production to net H+ consumption in the external solution. The uptake rates of NH
4
+
were correlated with equimolar net production of H+. With NO
3
−
nutrition net consumption of H+ was approximately twice as high as uptake rates of NO
3
−
In the forest stand the NO
3
−
concentration in the soil solution was more than 10 times higher than the NH
4
+
concentration (<100 μM), and the rhizosphere pH of non-mycorrhizal roots considerably higher than the bulk soil pH. The rhizosphere pH increase was particularly evident in apical root zones where the rates of water and NO
3
−
uptake and nitrate reductase activity were also higher. The results are summarized in a model of water and nutrient transport to, and uptake by, non-mycorrhizal roots of Norway spruce in a forest stand. Model calculations indicate that delivery to the roots by mass flow may meet most of the plant demand of nitrogen and calcium, and that non-mycorrhizal root tips have the potential to take up most of the delivered nitrate and calcium.
269 citations
TL;DR: This lecture reviews important aspects of the physiology of common kinds of mycorrhiza and considers their relevance to the ecological importance of these symbioses.
255 citations