Alnus Glutinosa Gaertn Research Articles

Seasonal changes in physiological groups of bacteria that participate in the nitrogen cycle in the rhizosphere of the alder

Seasonal changes of bacteria associated with the rhizosphere of Alnus glutinosa (L) Gaertn. were studied in a European alder copse situated in the center of Spain. Bacterial genera were determined following a modification of the Sato et al. (1987) protocol. The role of the bacteria in the nitrogen cycle was determined. The cenotic composition of the European alder rhizosphere alternated between autumn and winter, when Bacillus predominated, and spring and summer, when Pseudomonas predominated. Correlations with different biotic and abiotic parameters are discussed.

Decomposition of roots of black alder and hybrid poplar in short-rotation plantings: Nitrogen and lignin control

The decomposition of the roots (0–2 mm, 2–5 mm and 5–10 mm) of black alder (Alnus glutinosa (L.) Gaertn.) and hybrid poplar (Populus nigra L. X Populus trichocarpa Torr & Gray) was followed over a 462-day period in pure and mixed plantings in southern Quebec. Small roots of alder had the highest initial concentrations of nitrogen and lignin, and lost 9 and 10% less mass than medium and large roots, respectively. Large roots of poplar had the highest lignin-to-nitrogen ratio and showed the smallest loss of mass over the total incubation period. Slow root decomposition of black alder and hybrid poplar was characterized by a greater proportion of initial root nitrogen immobilized per unit of carbon respired. Lignin concentration in roots of alder and poplar increased rapidly at the beginning of the incubation. Our results suggest that high levels of nitrogen in roots of alder could contribute in slowing the rate of decomposition by allowing the formation of nitrogen-lignin derivatives and low levels of nitrogen in roots of poplar may limit the growth of microorganisms and the rate of root decomposition. A multiple regression was developed using initial nitrogen, lignin concentration and the ratio of lignin to nitrogen to produce an index of the rate of root decomposition. The correlation between the index values and the percentage of residual root mass was significant (r=0.98, p<0.01).

Nitrate reductase activity, nitrogenase activity and photosynthesis of black alder exposed to chilling temperatures

Actinorhizal (Frankia‐nodulated) black alder [Alnus glutinosa (L.) Gaertn.] seedlings fertilized with 0.36 mM nitrate (low nitrate fertilizer treatment) or 7.14 mM nitrate (high nitrate fertilizer treatment) and acclimated in a growth chamber for 2 weeks were exposed to 2.5 h of night‐time chilling temperatures of −1 to 4°C. Cold treatment decreased nitrogenase activity (acetylene reduction activity) 33% for low nitrate fertilized plants and 41% for high nitrate fertilized plants. Recovery of nitrogenase activity occurred within 7 days after chilling treatment. In contrast, in vivo nitrate reductase (NR) activities of leaves and fine roots increased immediately after chilling then decreased as nitrogenase activities recovered. Fine roots of alder seedlings exhibited NR activities proportional to the amounts of nitrate in the rooting medium. In contrast, the NR activities of leaves were independent of substrate and tissue nitrate levels and corresponded to nitrogenase activity in the root nodules. In a separate experiment, net photosynthesis (PS) of similarly treated black alder seedlings was measured before and after chilling treatments. Net PS declined in response to chilling by 17% for plants receiving low nitrate fertilizer and 19% for plants receiving high nitrate fertilizer. After chilling, stomatal conductance (gs) decreased by 39% and internal CO2 concentration (ci) decreased by 5% in plants receiving the high nitrate fertilizer, whereas plants receiving the low nitrate fertilizer showed no change in gs and a 13% increase in ci. Results indicate that chilling stimulates stomatal closure only at the high nitrate level and that interference with biochemical functions is probably the major impact of chilling on PS.

Autumnal allocation of phosphorus in black alder, eastern Cottonwood, and white basswood

Changes in leaf and current year bark phosphorus (P) concentrations of actinorhizal black alder (Alnusglutinosa (L.) Gaertn.), eastern cottonwood (Populusdeltoides Bartr. ex. Marsh.), and white basswood (Tiliaheterophylla Vent.) were determined during autumn on a mine-spoil site and a contrasting prairie site. During the last 2 weeks of sampling (4 weeks for alder at the prairie site), leaf P concentrations decreased by 43% for black alder and 23% for eastern cottonwood at the mine-spoil site and by 30% for black alder and 26% for white basswood at the prairie site. Concurrent increases in bark P concentration were observed only for eastern cottonwood and white basswood. Changes in leaf, bark, and root P of potted black alder seedlings were also followed in a parallel experiment. Bud set was associated with the onset of increasing leaf P concentration and content and stabilizing bark P content, while roots continued to accumulate P. The ratio of bark P content to root P content as well as the ratio of bark dry weight to root dry weight increased during the last stages of leaf senescence. Our results suggest that black alder can resorb a large proportion of its leaf P during leaf senescence, particularly when P availability is low. Both twigs and roots served as storage tissues for P, with roots acting as a primary sink in early autumn and bark acting as a sink for subsequently resorbed leaf P.

Pressurized ventilation in wetland plants

Species of wetland plants that aerate their submerged organs by thermo-osmotic transport of gas have been identified in six genera of the angiosperm families Butomacea, Nymphaeacea and Menyanthaceae. Flow rates of 14 ml gas h −1 in the monocotyledon Hydrocleys nymphoides (Humb. & Bonpl. ex Willd.) Buchenau to 5000 ml in the dicotyledon Victoria amazonica (Poepp.) Sowerby are comparable to those rates found in Nelumbo nucifera Gaertn. from the Nelumbonacean family, but an order higher than those in Alnus glutinosa (L.) Gaertn. from the Betulacean family as reported in the literature. The aeration is driven by a pressurizaion of the gas in th e aerenchyma of young floating leaves as a consequence of the physical effect of thermo-osmosis of gases. Differences in hygrometric state of the leaves and the ambient air effect the flow rates. Increased transpirational cooling of the upper leaf surface seems to give rise to a steeper temperature gradient within the leaf, intensifying the aeration. As these five plant families are not closely related, the ability to generate a pressurized ventilation by thermo-osmosis of gas can be seen as a special adaptation of the wetland plants to the anoxic environment.

Localization of the porous partition responsible for pressurized gas transport in Alnus glutinosa (L.) Gaertn.

The pressurized gas transport which improves the oxygen supply of the roots of the wetland tree black alder (Alnus glutinosa (L.) Gaertn.), is based on the existence of a thermo-osmotically active porous tissue partition in the lower part of the trunk with pore diameters in the range of, or smaller than, the mean free path length of the gas molecules (e.g., 70 nm for O(2) at 20 degrees C and 100 kPa). Anatomical studies have shown that only the cambial layer or the phellogen of the lenticels have intercellular spaces small enough to be responsible for thermo-osmotic activity. The final localization of the thermo-osmotically active partition and the determination of the pore sizes were done by diffusion and effusion experiments with basal trunk pieces of 3- to 4-year-old trees. The mean pore sizes of the intercellular system were not smaller than 100 nm in diameter in the cambial layer separating the bark from the wood, but 14 +/- 7 nm in diameter in the phellogen underlying the lenticels. Because of these small pores, the phellogen of the lenticels is the significant thermo-osmotically active partition for the transport of air to the root system in black alder.

Ratio of fixed and assimilated nitrogen in a black alder (Alnusglutinosa) stand

The ratio of fixed and assimilated nitrogen was determined in a black alder (Alnusglutinosa (L.) Gaertn.) stand throughout a growing season by measuring symbiotic dinitrogen fixation, soil mineral nitrogen concentration, and soil nitrifying capacity. The symbiotic dinitrogen fixation evaluated by the method based on natural isotopic abundance, δ15N) showed that most nitrogen present in alder leaves was derived from fixation (94%). Nitrogenase activity, measured by acetylene reduction assay, began at bud break and continued over the growing season, but showed great variation. The upper soil layer (0–15 cm) beneath black alder contained ammonium and nitrate nitrogen on sampling dates. Nitrification, determined by biological nitrous oxide (N2O) production after a short insitu incubation, occurred throughout the season. Black alders satisfied most of their nitrogen requirements from an atmospheric origin.

Effects of temperature regime and fertilization on nitrogenase activity of black alder seedlings during autumn in Illinois, U.S.A.

A pot experiment was conducted to determine the effects of two regimes of temperature and fertilization on nitrogenase activity (acetylene reduction) of naturalized black alder (Alnusglutinosa (L.) Gaertn.) seedlings during autumn in central Illinois, United States. An equal number of Frankia-nodulated plants were fertilized with either a complete or a nitrogen-free fertilizer solution. After 3 months of growth in a glasshouse, half of the plants in each fertilization group were transferred outside in mid-September. Rates of C2H2 reduction decreased throughout autumn for plants in all treatments, although exposure to freezing temperatures accelerated the decline of nitrogenase activity. Alders that did not receive nitrogen fertilization were still reducing C2H2 under natural light conditions in the heated glasshouse on December 10 at a rate of 7.5 nmol•mg−1•h−1. Compared with alders not receiving mineral nitrogen, complete fertilization resulted in a 45% reduction of initial autumnal rates of C2H2 reduction and early inactivity of nitrogenase. Leaf senescence and leaf abscission of naturalized black alder were not induced by decreasing photoperiod alone in Illinois. We conclude that N2 fixation of black alder in Illinois can proceed late into the autumn as long as green leaves remain attached to the plant and nodules are not subjected to low and freezing temperatures.

Juglone reduces growth, nitrogenase activity, and root respiration of actinorhizal black alder seedlings

European black alder trees [Alnus glutinosa (L.) Gaertn.] fix nitrogen with nodular symbionts and are interplanted with valuable black walnut trees (Juglans nigra L.) to increase soil nitrogen fertility. However, on some soils interplanted alder can be killed by black walnut's allelochemical juglone. In order to better understand the effects of juglone directly on the growth, nitrogen fixation, and root respiration of black alder, we grew nodulated alders hydroponically in a nitrogen-free nutrient solution at juglone levels of 2 × 10(-6), 2 × 10(-5), and 0 molar (M). Results indicate that nitrogenase activity (acetylene reduction) of alders growing in 2 × 10(-3) M juglone was reduced relative to alders without added juglone after one day, and in 2 × 10(-6) M juglone after five days. Root respiration (CO2 evolution) and the relative increase of plant fresh weight were reduced in the 2 × 10(-5) M juglone treatment. In a related experiment, black alder germinants were grown in Flanagan silt loam soil dosed with 10(-3), 10(-4), and 0 M juglone. The inhibitory effects of 10(-3) M juglone on radicle elongation ceased 22-37 days after juglone treatments were started, suggesting that this soil can readily detoxify juglone.

Seasonal changes in nodular nitrogenase activity of Alnus glutinosa and Elaeagnus angustifolia.

Root nodule development, and seasonal patterns of nodular nitrogenase and hydrogenase activities were determined for 5- to 8-year old black alder (Alnus glutinosa (L.) Gaertn.) and Russian olive (Elaeagnus angustifolia L.) interplanted with black walnut (Juglans nigra L.) on bottomland and upland sites in central Illinois, USA. Black alder produced nodules at both sites, but Russian olive did so only at the bottomland site. Nodular nitrogenase activity was detectable in both species over a 220-day period. Maximum, midday rates of nitrogenase activity (acetylene reduction) of 15 to 20 micromoles C(2)H(4) per g dry nodule per hour were maintained by black alder for approximately 150 days at both the upland and bottomland sites. Near maximum rates of nodular nitrogenase activity were maintained for a similar period by Russian olive at the lowland site, although specific nitrogenase activity was approximately 25% lower than in black alder owing to a larger proportion of necrotic nodular tissue in Russian olive. In both species, nitrogenase activity increased exponentially with temperature between 10 degrees C and 20 to 25 degrees C. No net hydrogen evolution by nodules of either species was detected at any time during the assay period, indicating efficient hydrogenase systems were operating under the conditions of the field assay. Height of black walnut interplanted with nodulated black alder and Russian olive was greater than that of black walnut grown in pure stands.

Characterization of a thermo-osmotic gas transport mechanism in Alnus glutinosa (L.) Gaertn.

A gas transport system based upon the physico-chemical effect of thermo-osmosis of gases in described for the black alder, Alnus glutinosa (L.) Gaertn. Air is transported through the alder's stem to the roots, thus improving O2 supply to respiring tissues of the root system. The gas transport system is investigated by means of a tracer gas technique (11% ethane in air, v/v). Gas transport depends on any source of radiant heat generating a temperature difference between the tree's stems and the atmosphere. The amount of gas transported in leafless trees is four times higher than the amount of gas reaching the roots by gas diffusion. Two-thirds of the gas is transported in the wood, only one-third in the bark. Intercellular spaces inside the porous lenticels of the bark are responsible for this kind of gas transport. Their diameters are estimated by the effusion rates of different tracer gases to be in the range of 1 μm.

Influence des réserves azotées sur la formation des feuilles d’Alnus glutinosa et ses conséquences dans l'estimation de la fixation d'azote

The influence of nitrogen reserves on leaf formation of 5- to 6-year-old plants of Alnus glutinosa (L.) Gaertn. was investigated using a 15N labelling method. Nitrogen reserves were derived essentially from the root system and along with N fixation by Frankia, supported the growth of the young leaves. The reserves represent 10% of the total nitrogen in the leaves at the end of the growing period under natural or environmentally controlled conditions. The percentage of fixed nitrogen in alder leaves was estimated to be 87% taking into account the nitrogen reserves and using the isotopic comparison with a nonfixing plant (Populus alba L.). Several conditions requiring the use of 15N methods to estimate the symbiotic nitrogen fixation by Frankia were formulated. The selection of samples for analysis must be from the most recently formed leaves at the end of the growing season to avoid the influence of nitrogenous reserves. Key words: nitrogen reserves, Alnus glutinosa, Populus alba, Frankia, 15N fixation.

Regulation ofin vitroshoot multiplication inSyringa, AlnusandMalusby different carbon sources

SummaryThe influence of different carbon sources on shoot multiplication was studied in the apple rootstock M.9. (Malus pumila Mill.), Syringa chinensis Willd. cv. Saugeana and Alnus glutinosa (L.) Gaertn. Both nodal and shoot tip explants were used. The sugars sucrose, glucose, fructose and the sugar alcohols mannitol and sorbitol at 88 and 175 mM were investigated. The carbon source influenced the percentage explants forming shoots, number of shoots per explant, number of separable nodes per shoot as well as shoot length. In Syringa, the carbohydrates influenced mainly the survival percentage of the explants, with the best carbon source being mannitol at both concentrations and sucrose at 88 mM. Overall the most effective carbon source in Alnus was glucose at 88 mM. Malus explants grew best on sorbitol, and fructose at 175 mM. The capability to metabolize a certain type of carbon source was reflected by the sugars and sugar alcohols reported in the sieve-tube exudate within a given genus (Zimmermann and...

Study of the contribution of the shoot and/or root ofAlnus sp. in the compatibility between the host and a Sp+ Frankia strain using a grafting technique

Two alder species,Alnus glutinosa (L.) Gaertn. andAlnus incana (L) Moench, were inoculated with a Sp+Frankia homogenate obtained fromA. incana root nodules. This inoculum formed effective nodules on the original host plant and ineffective nodules onA. glutinosa. Grafts between the two alder species were made to determine which part of the plant is involved in this phenomenon. The results obtained indicate that the compatibility between Alnus andFrankia is restricted to the root system.

Autumnal photosynthesis is extended in nitrogen-fixing European black alder compared with white basswood: possible adaptive significance

Net photosynthesis was measured at weekly intervals from late September to mid-November in the field on leaves of actinorhizal European black alder (Alnusglutinosa (L.) Gaertn.) and nonactinorhizal white basswood (Tiliaheterophylla Vent.) growing in central Illinois. Black alder retained its leaves and continued to photosynthesize for a month longer than white basswood. Maximum photosynthetic rates occurred in September and declined during the autumn for both species, although weekly values fluctuated widely. Mean maximum CO2 fixation rates for black alder and white basswood were 11.88 and 4.62 μmol CO2 • m−2 • s−1, respectively, at the initial measurement in late September. On each subsequent measurement date black alder had a significantly higher rate of CO2 fixation than basswood. Night temperatures of 0 °C and below caused a sharp decline in photosynthesis for black alder on the following day. Stomatal conductance was highly correlated with photosynthesis, but as these two parameters declined over the autumn, intercellular CO2 concentration increased. Thus, nonstomatal limitations are thought to be involved in the temperature-induced reduction in photosynthesis. Prolonged photosynthesis in autumn may give black alder a competitive growth advantage over other deciduous species, compensate for the high energy cost associated with nitrogen fixation, or be associated with black alder's inefficient conservation of foliar nitrogen via autumnal retranslocation.

Compatibility ofFrankiaespore positive and spore negative inocula withAlnus glutinosaandAlnus incana

Abstract Growth, nodulation, and nitrogen fixation by Alnus glutinosa (L.) Gaertn. and Alnus incana (L.) Moench inoculated with two Frankia inocula (a spore positive nodule homogenate and a spore negative isolate) were examined. The spore positive inoculum had a very low compatibility with A. glutinosa while a very large compatibility was found with the spore negative strain. Alnus incana had little specificity to the two types of Frankia which allowed the coexistence and the expression of the nitrogen fixation capacity of the two nodule types on the same root system. This result suggests that, despite the competition from indigenous strains, it may be possible to introduce in some areas a highly effective Frankia strain after careful study of the compatibility.

The responses of four Irish wetland tree species to raised soil water levels

SUMMARYThe four most common tree species in Irish wetland woods are Alnus glutinosa (L.) Gaertn. (common alder), Betula pubescens Ehrh. (downy birch), Fraxinus excelsior L. (ash) and Salix cinerea ssp. oleifolia Macreight (Salix atrocinerea Brot., common sally). Seedlings of these species were subjected to different soil water levels (half saturated and surface saturated) in their second and third years of growth, and performance was compared to that in a free draining control treatment. All plants survived in the water treatments, except for over 50%, of the B. pubescens. Soil redox potentials indicated a gradient in the degree of hypoxia which seemed to reflect the order of tolerance of the species, as shown by measurements of relative growth and final dry weight. The observed differences in soil redox potentials may have been due to the oxidizing activity of the roots of tolerant species, which showed varying degrees of stem base hypertrophy and associated proliferation of lenticels. Species were affected by the waterlogging treatments in the order B. pubescens (most adversely affected) &gt; A. glutinosa &gt; F. excelsior &gt; S. cinerea ssp. oleifolia.

Détermination de l'identité isotopique de l'azote fixé par le Frankia associé au genre Alnus

To use the 15N natural abundance method to evaluate the symbiotic nitrogen fixation by actinorhizal trees, it is necessary to determine the isotopic identity of assimilated nitrogen from two sources: the soil and the air. This study reports an isotopic value of fixed nitrogen by two alder species (Alnus incana (L.) Moench and Alnus glutinosa (L.) Gaertn. growing on nitrogen-free medium in greenhouse experiments. The δ15N value of the aerial parts was −2. This value was stable with time and did not depend on the Frankia strains used. This value could be used to estimate the nitrogen fixation in the natural ecosystem. Other parameters such as the mobilization of nitrogen reserves and the choice of the reference plant must be investigated to apply this method. The nodules of these two alder species were enriched in 15N relative to the rest of the plant but there was no relationship between symbiotic effectiveness of Frankia strains and 15N enrichment of nodules. On the other hand, for naturally growing trees, an enrichment in 15N was found primarily in the vesicles of nodules that are the sites of nitrogen fixation.

Autumnal changes of sulfur fractions and the ratio of organic sulfur to total nitrogen in leaves and adjacent bark of eastern cottonwood, white basswood and actinorhizal black alder.

Autumnal changes in organic-S, sulfate-S, total-S and the ratios of organic-S to total-N and sulfate-S to organic-S were followed in leaves and adjacent bark of actinorhizal (Frankia-nodulated) black alder (Alnus glutinosa (L.) Gaertn.) and eastern cottonwood (Populus deltoides Bartr. ex Marsh.) trees growing on a minespoil site high in extractable soil sulfate, and in black alder and white basswood (Tilia heterophylla Venten.) trees growing on a prairie-derived soil in Illinois. Organic-S concentrations decreased significantly (P < 0.05) during autumn only in foliage of trees growing on the prairie-derived soil where losses of leaf organic-S were 65% for black alder and 100% for white basswood. Leaf sulfate concentrations were relatively stable throughout autumn in white basswood growing on prairie-derived soil and in black alder at both sites. Sulfate-S concentrations in leaves were significantly (P < 0.05) higher in trees at the minespoil site than in trees growing in the prairie-derived soil (5.1 mg g(-1) for the minespoil site and 1.2 mg g(-1) for the prairie-derived soil), and in the non-actinorhizal species during late summer. During the autumn, the ratio of organic-S to total-N doubled in leaves of eastern cottonwood at the minespoil site, but in black alder and white basswood growing on the prarie-derived soil, it decreased by 60 and 74%, respectively. Organic-S concentrations in bark increased more during autumn in species unable to fix atmospheric N(2), than in black alder. The results suggest that patterns of autumnal translocation of leaf S can be site-dependent and that leaf S and leaf N are, at least in part, translocated independently in the fall. Black alder and eastern cottonwood seemed to incorporate sulfate-S readily into organic substances in leaves when grown in soils with a high sulfate content.

Stomatal conductance and growth of five Alnusglutinosa clones in response to controlled water stress

An experiment to quantify the response of unnodulated, fertilized European black alder (Alnusglutinosa (L.) Gaertn.) seedlings to progressive water stress showed contrasting drought tolerance among five clones, using stomatal conductance, leaf area, and height as indices of drought sensitivity. In particular, one rapidly growing clone (AG 8022-14) showed the ability to moderate changes in water stress more efficiently than the more slowly growing clones. After 30 days of moderate levels of water stress, clones that had higher stomatal conductance also had greater leaf area and height growth. Leaf area and height were both sensitive to plant water status, although no threshold of stress associated with a cessation of leaf area or height expansion was found even though stomatal conductance decreased to 0.05 cm s−1 under severe water stress.