Josef Bauch

Dendroecological investigations on Swietenia macrophylla King and Cedrela odorata L. (Meliaceae) in the central Amazon

The width of the increment zones in the xylem of Swietenia macrophylla King and Cedrela odorata L. was investigated by dendroecological methods in a primary forest near Aripuanã, Mato Grosso, Brazil (10°09′S, 59°26′W). The annual period of cambial cell division and its intra-annual variation were determined by dendrometer measurements of 30 trees of each species. Tree-ring width chronologies for Swietenia and Cedrela were developed from cross-dated increment curves of 33 out of 47 Swietenia and 51 out of 64 Cedrela trees. Simple correlations were computed between the radial growth increment and monthly precipitation for the period 1890–2000. In Swietenia, cambium activity occurred throughout almost the whole year, but in Cedrela it was restricted to the rainy period from September of the previous year to June of the current year. Tree-rings were formed annually in the juvenile and adult wood of Cedrela, while in Swietenia the annual formation of tree-rings was restricted to the adult wood. Consequently the age of the Swietenia trees could be dated by the tree-rings in good approximation, while age dating of the Cedrela trees was exact. Correlation analyses revealed a significant relationship between the precipitation at the beginning and at the end of the growth season and the width of the increment zones in the adult xylem of Swietenia. In contrast, the width of the growth increment in the xylem of Cedrela was significantly correlated with the precipitation in March and May of the previous growth period.

The morphological variability of the bordered pit membranes in gymnosperms

SummaryThe membranes of bordered pits were investigated in 120 species of 47 genera of the gymnospermous families, using light and electron microscopic techniques. A great variability in the morphological structure of the pit membranes has been established. The differences in structure are pronounced and depend mainly on the genus involved.A classification of six morphological “structure types” is presented. They do not necessarily correspond with the chemical composition and the functional behaviour. The results on the variability of the pit membrane have shown the necessity of an extended definition for the torus.

Monitoring uptake and contents of Mg, Ca and K in Norway spruce as influenced by pH and Al, using microprobe analysis and stable isotope labelling

In a model system using intact spruce trees (Picea abies [L.] Karst.) we followed the path of magnesium, calcium and potassium during uptake into the root and during long-range transport into the shoot, by multiple stable isotope labelling. The roots of two- and three-year-old spruce trees originating from soil culture were removed from the soil and, in part or in toto, exposed to labelling solutions containing the stable isotopes 25Mg or 26Mg, 41K and 42Ca or 44Ca. Optical-emission-spectroscopy (ICP-OES) of plant fractions and labelling solutions was combined with the quantitative analysis of stable isotope ratios in sections of shock frozen, cryosubstituted material using the laser-microprobe-mass-analyser (LAMMA). This combination allowed us to distinguish, both in bulk samples and on the cellular level between (i) the fraction of elements originally present in the plant before the start of the labelling, (ii) the material taken up from the labelling solution into the plant and (iii) any material released by the plant into the labelling solution.In single-root labelling experiments, roots of three-year-old spruce trees, grown in nursery soil, were exposed to various pH conditions. The exchange of Mg and Ca with the labelling solution was nearly 100% in the cell walls of the mycorrhized finest roots. This exchange was only slightly affected by a step down to pH 3.5. The absolute Mg and Ca content in the cell walls was moderately reduced by incubation at pH 3.5 and strongly reduced in the presence of Al at this pH. After a pH 3.5 and 2 mM Al treatment we found Al in the xylem cell walls and the cortex cell lumina at elevated concentrations. To analyse the combined effect of high Al and high proton concentrations on the long-range transport, we used a “split-root system”. The root mass of an intact two-year-old spruce tree, grown in mineral soil, was divided into even parts and both halves incubated in solutions with two sets of different stable isotopes of Mg and Ca (side A: no Al, 25Mg and 42Ca; side B: +Al, 26Mg and 44Ca) and 41K on both sides. We observed a large uptake of Mg, Ca and K into the plant and a pronounced release. The net uptake of all three elements was lower from the Al-doted solution. In cross-sections of the apical shoot we found after seven-day labelling period about 60–70% of the Mg and Ca and 30% of the K content in the xylem cell walls originating from both labelling solutions. The clear majority of the Mg and Ca label originated from the Al-doted side.

Microbeam analysis of Ca exchange and uptake in the fine roots of spruce: influence of pH and aluminum

SummaryA novel stable isotope labelling procedure for microbeam analysis was developed to monitor exchange and uptake of nutrients, primarily Mg, K and Ca, by root tips at the cellular level. Initially root samples were analysed from 2-year-old spruce trees, originating both from a nursery and from a polluted forest site, (1) for the cortex cell wall accessibility and nutrient binding properties, (2) for the influence of low pH and elevated aluminum concentrations on Ca binding to cortex cell walls, and (3) for long-range transport into the secondary xylem, proximal to the labelled root tip. In nursery control plants, Ca is localized mainly in the apoplast of the cortex. Exchange of Mg, K, Ca in the cell wall of the cortex and the primary xylem with label in incubation solutions is almost completed to equilibration within 30 min. In the secondary xylem we could detect Mg, K, and Ca from labelling solutions in minute amounts after 30 min, and as a major fraction after 48 h. This indicates that stable isotope labelling can be used to study both ion-exchange properties of the apoplast and long-range transport. Slight acidification of the labelling incubation media to pH 4.5 reduced Ca binding to the cortex cell walls slightly, but acidification to the extreme value of pH 2.3 reduced binding 41%. A combination of pH 4.5 and increased free aluminum reduced the binding by 83%. In a preliminary attempt to analyse the nutrient binding capability of the root-tip apoplast from pollution affected trees, we exposed fine roots of 2-year-old spruce from an acidified and polluted site showing typical low levels of Ca and Mg in the cortical cell walls to Ca-enriched media. Under these conditions the Ca content of cortex cell walls doubled upon incubation at pH 4.7, reaching 40% of the total binding capacity of our nursey control plants.

FORMATION OF INCREMENT ZONES AND INTRAANNUAL GROWTH DYNAMICS IN THE XYLEM OF SWIETENIA MACROPHYLLA, CARAPA GUIANENSIS, AND CEDRELA ODORATA (MELIACEAE)

The pattern of growth increment zones, the cambial growth dynamics and the structural variation in wood formation of Swietenia macrophylla King, Carapa guianensis Aubl., and Cedrela odorata L. (Meliaceae) were investigated in order to understand the relationship of site conditions and sustainable growth in Central Amazonian plantations. Trees were available from 8-, 17-, 23-, and 57-year-old plantations, and from primary forests in Manaus (Amazonia), Santarem (Para), and Aripuana (Mato Grosso). The wood anatomical structure and the annual increments of 61 Swietenia, 94 Carapa, and 89 Cedrela trees were studied for different tree heights. The curves of annual increments were cross-dated and tested for synchronisation. The cambial growth dynamics of up to 52 trees per species were dated by means of dendrometer measurements, monthly labelling by pinmarkers, and extracted cambium samples investigated using a microscope. The intraannual course of the growth and structural variation was compared with the water supply of the soil and insect attacks (Hypsipyla grandella (Zeller) Lep.).In Swietenia and Carapa parenchyma and vessel bands as well as bands of resin canals were observed. Within the xylem of Cedrela, alternating bands of fibres and vessels surrounded by paratracheal parenchyma were found; bands of resin canals were only occasional. In the juvenile wood of Swietenia and Carapa no synchronization of the increment curves was possible, whereas the increment curves obtained in the juvenile wood of Cedrela showed parallel run in growth. The increment curves obtained in adult wood of Swietenia and Cedrela indicate an annual formation of increment zones, whereas the number of increment zones in the xylem of Carapa was approximately 50% higher than the tree age (years) indicating that the growth increments of Carapa also were not annual during the adult phase of growth.The study of the intraannual growth dynamics of the trees showed that the formation of parenchyma bands in Swietenia is induced by dry periods before a cambial dormancy. The formation of parenchyma bands of Carapa was induced by extremely dry and extremely wet periods before a cambial dormancy, whereas fibre bands in Cedrela were induced by dry periods before a cambial dormancy and the formation of vessel bands embedded in paratracheal parenchyma was induced by wet periods after a cambial dormancy. In addition, insect attack (Hypsipyla grandella) induced locally restricted formation of parenchyma bands and bands of resin canals in Swietenia, Carapa and Cedrela.

Topochemical characterisation of phenolic extractives in discoloured beechwood (Fagus sylvatica L.)

Summary The topochemical distribution of phenolic extractives in steamed and kiln-dried beechwood with discolourations was investigated on a cellular level by using scanning UV microspectrophotometry (UMSP). For the chemical characterisation of accessory compounds, acetone and methanol extracts of the discoloured beechwood were separated by accelerated solvent extraction (ASE) and analysed with high performance liquid chromatography (HPLC). The UV microscopic investigations reveal that the accessory compounds responsible for the discolouration of beechwood are mainly restricted to the longitudinal and ray parenchyma cells and the lumen of vessels. The detected extractives are characterised by high UV absorbance values and an absorbance maximum in a wavelength range between 280 and 290 nm. The separation of the acetone and methanol extracts of discoloured beechwood shows the presence of different low molecular phenols such as catechin and 2,6-dimethoxybenzochinon, which are transformed into high condensation compounds during steaming and kiln-drying.

The kinetics of calcium and magnesium entry into mycorrhizal spruce roots

Abstract. The entry of calcium and magnesium from external sources into mycorrhizal roots of 3-year-old Norway spruce trees (Piceaabies [L.] Karst.) was monitored. Roots of intact plants were exposed for various periods of time, ranging from 2 min to 48 h, to nutrient solutions which contained the stable-isotope tracers 25Mg and 44Ca. After labelling, samples of roots were excised from the plants, shock-frozen, cryosubstituted and embedded. The resulting isotope composition in this material was analysed by a laser-microprobe-mass-analyser (LAMMA) at relevant positions within cross-sections of the roots. For both elements, we determined (i) the fractions of the isotopes originating from the plant prior to labelling, and (ii) the fraction of isotopes originating from the corresponding tracer that penetrated into the root. Both divalent cations rapidly penetrated across the cortical apoplast and reached the endodermis. After 2 min of exposure to the labelling solution, an initial transient gradient of the tracers could be observed within the root cortex. Subsequently, calcium as well as magnesium equilibrated between the apoplast of the entire cortex and the external tracer with a half-time, t1/2, of about 3 min. In contrast, the kinetics of radial movement into the vascular stele showed a delay with a t1/2 of 100–120 min. We take this as strong evidence that there exists a free apoplastic path for divalent cations in the cortex and that the endodermis is a major barrier to the further passage of Mg and Ca into the xylem. While 25Mg in the labelling solution exchanged rapidly with Mg in the cortical apoplast, the exchange across the plasma membrane with Mg present in the protoplasm of the same cortical cells was almost 2 orders of magnitude slower. The kinetics of Ca and Mg entry at +6 °C were similar to those obtained at a root temperature of +22 °C.

Zellulärer Nachweis einiger Elemente in den Feinwurzeln gesunder und erkrankter Tannen (Abies alba Mill.) und Fichten (Picea abies [L.] Karst.)

ZusammenfassungAn den Feinwurzeln von insgesamt zehn gesunden und erkrankten NadelbäumenAbies alba Mill. undPicea abies [L.] Karst. einiger Standorte wurde die Elementverteilung in den einzelnen Zellen mit einer Lasermikromassenspektrometrie und einer röntgenenergiedispersiven Analyse untersucht.Bei gesunden Pflanzen findet man in den Zellwänden der Rindenschicht und des primären Xylems die Makronährstoffe Magnesium, Kalium und insbesondere Calcium; außerdem lassen sich Natrium und Aluminium nachweisen. Diese Elemente kommen ebenso in den Zellwänden des primären Xylems vor, allerdings ist die Konzentration an Aluminium gering.Bei den kranken Tannen enthält die Rindenschicht Calcium und Magnesium nur in Spuren oder überhaupt nicht; das Aluminium reichert sich in einigen Rindenzellen im Vergleich zu gesunden Pflanzen an. Das primäre Xylem der kranken Tannen enthält nur geringe Calciummengen, das Aluminium ist jedoch in deutlicher Konzentration vorhanden, ebenso Magnesium.Bei den kranken Fichten ist in der Rindenschicht und im Xylem Calcium nicht und Magnesium nur in geringen Mengen gegeben. Die durchschnittliche Aluminiumkonzentration war sogar niedriger als in gesunden Vergleichsbäumen.Die Verarmung an den Makronährelementen Calcium und Magnesium in den Feinwurzeln erkrankter Bäume, die auf sauren Böden stocken, muß sich auf die Pflanze schädigend auswirken, wobei eine veränderte Wechselwirkung der vorhandenen Elemente diese Schädigung verstärken dürfte. Die Schlüsselstellung von Aluminium als toxisches Element erscheint hiernach nicht wahrscheinlich, gleichwohl könnte es in seiner Wechselwirkung mit anderen Elementen von Bedeutung sein.SummaryThe distribution of some elements in individual cells of the fine roots of altogehter ten healthy and diseased conifers (Abies alba Mill. andPicea abies [L.] Karst.) from a few sites was investigated by means of laser-microprobe-mass-spectrometry and X-ray analysis.In healthy trees the major nutrient elements magnesium, potassium and, in particular, calcium are present in the cell walls of the cortex; moreover, sodium and aluminium were identified. These elements are also present in the cell walls of the primary xylem; concentration of aluminium, however, was low.In diseased first the cortex contains calcium and magnesium only in traces or not at all; the aluminium content increases only in some cortical cells compared with healthy trees. The primary xylem of diseased firs contains only small amounts of calcium; aluminium as well as magnesium are distinctly present.In diseased spruce trees the cell walls of the cortex and primary xylem do not contain calcium and only small amounts of magnesium. The average concentration of aluminium was even lower than in the controls from healthy trees.The lack of the major nutrient elements calcium and magnesium in the fine roots of diseased trees growing on acidified soils must necessarily be detrimental to the plants health; the altered interaction of the elements present may even intensify any given damage. A key position of aluminium being the toxic element cannot be derived from these results but through interaction with other elements it could likely to be of some importance.

Variability of the chemical composition of pit membranes in bordered pits of gymnosperms

SummaryThe pit membranes of the bordered pits in about one hundred coniferous wood species were investigated in regard to their chemical composition, in particular to the aromatic compounds. In many species pit membranes, even in the sapwood, contain phenolic substances. In heartwood, normally lignification takes place besides the development of other polyphenols. The variability of these compounds, both in sapwood an in heartwood, may be considerable not only between species but also within the same species and even between neighbouring tracheids and pits respectively.

On the distribution and transport of mineral elements in xylem, cambium and phloem of spruce (Picea abies [L.] Karst.)

The distribution of calcium, magnesium and potassium in the cambial region of a 20-year-old Norway spruce was determined by optical emission spectrometry (ICP-OES) in tissue samples ranging from the outer bark up to latewood and earlywood of the outer tree-rings. The highest contents of magnesium and potassium were found in the cambium and, in the case of calcium, in the developing phloem. In more detail we investigated the distribution and incorporation of calcium, magnesium and potassium in a model system of intact two-year-old plants (Picea abies [L.] Karst.). The roots of the seedlings, grown under controlled conditions, were removed from the soil and exposed to labelling solutions containing the enriched stable isotopes 25 Mg, 41 K, and 44 Ca as tracers. After seven days of labelling the cell walls of earlywood, latewood, cambium and phloem were analysed in stem cross sections of shock-frozen, cryo-substituted tissue by three microprobes: (i) by energy dispersive x-ray analysis (EDXA, 0.3 μm lateral resolution), (ii) isotope specific point analysis, using the laser microprobe mass analyser (LAMMA, 1.5μm lat. res.) and (iii) isotope specific imaging by secondary ion mass spectrometry (SIMS, 1-3μm lat. res.). After seven days of labelling approximately 60-75% of the Ca-content, 5-65% of the Mg-content and about 25-30% of the K-content within the cell walls of the shoot originated from the labelling solutions. The upper part (one-year-old) of the shoot axis contained a 10% smaller fraction of labelled Ca and a 10% larger fraction of labelled Mg in comparison to the more basal regions of the shoot (two-year-old). For all three elements we could not detect any significant radial gradient of the labelled fraction while comparing earlywood, latewood, cambium and phloem. We interpret our results as evidence for (i) a relevant bidirectional longitudinal transport and (ii) a radial element exchange between xylem, cambium and phloem, completed within the seven days of labelling.