Showing papers in "Trees-structure and Function in 1991"

Ammonium and nitrate uptake rates and rhizosphere pH in non-mycorrhizal roots of Norway spruce [ Picea abies (L.) Karst.]

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.

Phloem loading and its development related to plant evolution from trees to herbs

Abstract: Minor vein structure in various taxonomic groups was described in a previous paper (Gamalei 1989). Here, these results are used to correlate minor vein structure with plant evolutionary, ecological and growth form schemes. The following pattern emerges: reductive evolution from evergreen trees to annual herbs is accompanied by gradually increasing symplastic isolation of the mesophyll and the phloem. This evolutionary tendency is confirmed by the ecological spreading and life-form distribution of modern plants with different types of minor vein structure. The meaning of this phenomenon is discussed. Chilling sensitivity of plasmodesmal translocation is considered to be the main reason. It is suggested that phloem loading for assimilate transport is double-routed. The symplastic route is more ancient and more economical for loading. The apoplastic pathway becomes the main or the only route under unfavorable conditions. The existence of a symplast/apoplast regulatory loading mechanism is suggested. The two loading routes differ in their selectivity for products of photosynthesis which changes their symplast/apoplast ratio which, in turn, determines the composition of the sieve tube exudate. The latter will influence growth and morphogenesis. Correlated changes of structure and function related to photosynthesis, loading, translocation and growth, are analysed with respect to life-form evolution. The influence of the pathway of loading on other processes is discussed.

Impairment of gas exchange and structure in birch leaves (Betula pendula) caused by low ozone concentrations

Abstract: Injury caused by low O3 concentrations (0, 0.05, 0.075, 0.1 μl 1-1) was analyzed in the epidermis and mesophyll of fully developed birch leaves by gas exchange experiments and low-temperature SEM: (I) after leaf formation in O3-free and ozonated air, and (II) after transferring control plants into ozonated air. In control leaves, autumnal senescence also was studied in O3-free air (III). As O3 concentration increased, leaves of (I) stayed reduced in size, but showed increased specific weight and stomatal density. The declining photosynthetic capacity, quantum yield and carboxylation efficiency lowered the light saturation of CO2 uptake and the water-use efficiency (WUE). Carbon gain was less limited by the reduced stomatal conductance than by the declining ability of CO2 fixation in the mesophyll. The changes in gas exchange were related to the O3 dose and were mediated by narrowed stomatal pores (overriding the increase in stomatal density) and by progressive collapse of mesophyll cells. The air space in the mesophyll increased, preceded by exudate formation on cell walls. Ozonated leaves, which had developed in O3-free air (II), displayed a similar but more rapid decline than the leaves from (I). In senescent leaves (III), CO2 uptake showed a similar decrease as in leaves with O3 injury but no changes in mesophyll structure and WUE. The nitrogen concentration declined only in senescent leaves in parallel with the rate of CO2 uptake. A thorough understanding of O3 injury and natural senescence requires combined structural and functional analyses of leaves.

Effects of aluminium on growth and nutrient uptake of small Picea abies and Pinus sylvestris plants

Abstract: The effects of aluminium concentrations between 0.2 and 30 mM at pH 3.8 ±0.2 on small plants of Norway spruce [(Picea abies (L.) Karst], Scots pine (Pinus sylvestris L.), and Scots pine infected with the ectomycorrhizal fungus Suillus bovinus (L. ex Fr.) O. Kuntze were investigated. The plants were grown at maximum relative growth rate (RG % day−1) with free access but very low external concentrations of nutrients. Steady-state conditions with respect to relative growth rate (RG) and internal nutrient concentrations were achieved before addition of aluminium, which was added as AlCl3 and/or Al(NO3)3. There were reductions in rg at aluminium concentrations of 0.3 mM in spruce, 6 mM in pine and 10 mM in ectomycorrhizal pine, i. e. at aluminium concentrations considerably higher than those normally occurring in the top layer of the mineral soil where most fine roots are found. Nutrient uptake rate per unit root growth rate was calculated for different nutrient elements. The uptake rate of calcium and magnesium was reduced at aluminium concentrations of 0.2 mM (spruce), 1 mM (pine) and 3 mM (ectomycorrhizal pine), without influencing Rg. The results question the validity of the hypothesis of aluminium toxicity to forest tree species at low external concentrations.

Root responses of flood-tolerant and flood-sensitive tree species to soil redox conditions

Abstract: Under controlled rhizotron conditions, roots of Taxodium distichum L., Quercus lyrata Walt, and Q. falcata var. pagodaefolia Ell. were subjected to low soil redox potentials. Root elongation was inhibited at low soil redox potentials. In T. distichum, redox potentials below +200 mV resulted in a significant inhibition of root elongation. In Q. falcata var. pagodaefolia and Q. lyrata, redox potentials below +350 mV resulted in complete cessation of root growth. Studies on root anatomy indicated that low soil redox potenials resulted in a changed cellular structure in the cortex of T. distichum. However, little change was noted in stress roots of oak species. Alcohol dehydrogenase activity in T. distichum roots was approximately doubled compared to control plants, indicating stimulated alcoholic fermentation. In T. distichum, alcoholic fermentation and anatomical changes contribute to flood tolerance but oak species lack these characteristics.

Function of spiral grain in trees

Abstract: Through spiral grain, conduits for sap lead from each root to all branches. This uniform distribution of sap is indicated by the paths of vessels and tracheids, and has been proven experimentally by means of dyed sap injected into the base of stems or taken up by roots. Trees receiving water only from roots at one side of the root collar nevertheless stay green and continue growing. Spiral grain in bark distributes food from each branch to other flanks of the stem and to most roots. Experimental interruptions of the sap and food conduits caused the cambial zone to reorient new conduit cells in new directions, bypassing the interruption. In particular, spiral grooves cut into the stem surface caused spiral grain. The new cells reorient through division and growth. Although spiral grain is largely under genetic control, trees appear to have a spiral grain especially where needed for distribution of water when root spheres are dry at one side. Compared with straight-grained trees, spiral-grained stems and branches bend and twist more when exposed to strong wind, in this way offering less wind resistance and being less likely to break. Through the bending and twisting, snow slides down from branches rather than breaking them, but the main function of spiral grain is the uniform distribution of supplies from each root to all branches, and from each branch to many roots.

Formation of heartwood substances in the stem of Robinia pseudoacacia L.

Abstract: The activities of two key enzymes in flavonoid biosynthesis, phenylalanine ammonia-lyase (PAL, E.C. 4.3.1.5) and chalcone synthase (CHS, E.C. 2.3.1.74) were determined in the trunkwood of Robinia pseudoacacia L. The trees under investigation were cut at different times of the year (September, November, January and April). At all times PAL is active, both in the youngest wood layer (the outermost growth ring) and at the sapwood heartwood boundary. On the other hand, CHS is active exclusively in the vicinity of the heartwood boundary. The results indicate that PAL is involved both in the formation of lignin (outermost annual ring), and in flavonoid biosynthesis (heartwood boundary). Highest activity of both PAL and CHS could be measured at the sapwood heartwood boundary in the tree felled in November, indicating that heartwood formation was occurring mainly at that time. The flavonoids accumulated in the heartwood are obviously formed in situ and seem to be transported only to a minor extent — if at all — via the phloem and the ray cells to the heartwood.

Analysis of stand density effects on canopy structure: a conceptual approach

Abstract: A few assumptions were used to generate a series of specific, quantitative predictions for the relationships between stand density and various dimensional measures of canopy structure. The predictions, each indicating an increase in mean crown size as density decreased, appeared to be reasonable and intuitive. Predictions were compared to data for two conifer species with different crown forms, Pinus contorta var. latifolia and Abies lasiocarpa. Results of these comparisons were mixed — the linear, directly measured dimensions were consistent with predicted relationships, but dimensions calculated from the linear measures were not. Re-examination of the original assumptions indicated that the model should account for crown shyness (engagement/disengagement) to adequately reflect the influence of stand density on canopy structure. The results also indicated a strong association between stand height and measures of mean crown size. Mean crown size of lodgepole pine was altered much more by density than was mean crown size of subalpine fir, due primarily to the different relative shade tolerances of the two species. Some of the observed differences between species may also reflect the range of densities examined and uneven spacing in the unmanaged natural stands.

Polycentric vascular rays in Suaeda monoica and the control of ray initiation and spacing

Abstract: The early-formed xylem of Suaeda monoica Forssk. ex J. F. Gmel (Chenopodiaceae) is temporarily rayless. Vascular rays differentiate during later stages of its xylem ontogeny. The rays in Suaeda are heterogeneous, and some of them are aggregated. The mature xylem of this species is characterized by two unique types of vascular rays: (1) rays with several inside initiation “centres” of small cells formed by local frequent cell divisions in the cambium, and (2) huge xylem rays with radial phloem strands that are connected to the axial phloem. The spacing of the xylem rays is not even, and possible mechanisms controlling ray spacing are discussed. Our observations indicate that rays do not have an inhibitory zone around them in which ray initiation is prevented. The initiation of radial patterns of small cells which appear like inside “rays” within a large vascular ray suggests that initiation and spacing of rays is controlled by radial signal flows in relationship with axial signal fluxes.

Crown profile of foliage area characterized with the Weibull distribution in a hinoki ( Chamaecyparis obtusa ) stand

Abstract: Thirten sample trees of various sizes in a 29-year-old hinoki [Chamaecyparis obtusa (Sieb, et Zucc.) Endl.] plantation were felled and subjected to the stratified clip technique. Crown profile of foliage area fitted well with the Weibull distribution. The crown profile tended to be more skewed toward the top of crowns in smaller trees than in larger trees. This tendency was reflected in the value of the shape parameter of the Weibull distribution. The shape parameter ranged from 1.73 to 3.23 and gradually increased up to an asymptotic value with an increase of stem diameter at breast height. The scale parameter of the distribution ranged from 1.0 to 4.2 and tended to increase in proportion to stem diameter at breast height. Foliage area of a tree correlated well with stem diameter at breast height through an ordinary allometric equation. Tree height could be approximated fairly well by a generalized allometric equation as a function of stem diameter at breast height. On the basis of the census of stem diameter at breast height, canopy profile could be constructed synthesizing crown profiles of foliage area for individual trees in the stand. Leaf area index was estimated to be 6.6 ha ha−1.

Confocal laser scanning microscopy of fluorescently stained wood cells: a new method for three-dimensional imaging of xylem elements

Abstract: Xylem cells were fluorescently stained with periodic acid — Schiff reaction or with Schiffs reagent alone and studied by confocal laser scanning microscopy. Single images with extremely low depth of focus, series of optical sections, computed stereo scopic images and “shadow casting” images as well as x-z images are obtained. In contrast to scanning electron microscopy, not only are the surfaces imaged, but elements concealed by other structures can be visualized by this system. Quantitative data on cell depth are provided and differences in lignification are detected.

Preformed and neoformed extension of shoots and sylleptic branching in relation to shoot length in Tsuga canadensis

Abstract: Shoot systems developed over 3 successive years were investigated on 55 understorey Tsuga canadensis (L.) Carr. trees. Paired comparisons of preformed-leaf content of terminal buds and numbers of leaves produced on new shoots showed that neoformed leaves were produced in large numbers. Parent-shoot character was not useful in predicting numbers of preformed leaves, was better related to total leaves produced, but left the majority of the variation unexplained. This reflected the capacity of any terminal bud to produce a shoot with more or less neoformation, depending on conditions for growth. All shoots over 6 cm long produced sylleptic shoots that bore from two to many leaves and were arranged in a mesitonic pattern along the parent. Some of the longer sylleptic shoots produced lateral buds or second-order sylleptic shoots. Monopodial second-year extensions of sylleptic-shoot axes followed an acrotonic pattern, as did proleptic shoots from the few lateral buds borne on the parent shoots. Such lateral buds were more frequent on shorter parent shoots: they typically occurred near the proximal and distal ends. Duration of shoot extension was positively correlated with shoot length: terminal buds became evident as shoot extension neared cessation.

Tracheid production in response to indole-3-acetic acid varies with internode age in Pinus sylvestris stems

Abstract: Different concentrations of indole-3-acetic acid (IAA) in lanolin were applied to the cambial region of approximately 10- and 34-year-old internodes in the main stem of Pinus sylvestris (L.) trees during the tracheid production period. After 5 weeks of treatment, the radial width of xylem produced in both ages of internode was positively related to exogenous IAA concentration measured at 0, 1 and 3 cm directly below the application site. Tracheid production in response to exogenous IAA in the 34-year-old internode was approximately one-half of that in the 10-year-old internode. The endogenous IAA level in the 7-, 17- and approximately 34-year-old internodes of similar trees was measured by radioimmunoassay, using gas chromatography-selected ion monitoring-mass spectrometry for validation. No consistent relationship was found between xylem radial width and IAA concentration. The data indicate that the cambium's ability to respond to exogenous IAA is qualitatively the same in 1-year-old shoots and older internodes. However, as the internode ages, there is a decrease in the extent of the response and in the optimal IAA level for inducing tracheid production.

Growth patterns and bending mechanics of branches

Abstract: This paper describes a simple model that calculates the evolution of branch shape as the result of growth patterns and weight variations. Experimental data concerning growth parameters were collected on a 23-year-old maritime pine tree (Pinus pinaster Ait.). Results are analysed in the first part of the study. Linear relationships are found between length and diameter, length and weight, and finally between the weight of branchwood and the square diameter. The analysis of vertical distribution of weight in the crown shows that the amount of branchwood main axis only remains lower than the amount of foliage needles and laterals in the upper whorls, whereas for older branches the relative amount of foliage tends to decrease. These results provide baseline data for computer simulation of branch growth. The theoretical bases of the model are presented in the second part of this work. The effects of growth parameters increase in length, diameter and weight and mechanical properties of the branch on the final shape are analysed. As expected, among all parameters, branch diameter has the greatest influence on the bending deflection. On the other hand, orthotropic growth of the terminal shoot tends to reduce the maximum bending moment in the branch. The distribution of weights in the branch also affects the deflection and maximum bending moment. These results are of interest for further analysis of branch form as an optimization problem based on biological growth.

Changes in hydraulic conductivity upon freezing of the xylem of Populus x canadensis Moench “ robusta ”

Abstract: The impact of freezing stress on the hydraulic conductivity was studied in 4- to 6-year-old branches of Populus x canadensis Moench “robusta” under gravity flow conditions. In fresh branch segments, the hydraulic conductivity was approximately 3–6×10-2 1 h-1kPa-1m and the specific conductivity approximately 22 1 h-1kPa-1m-1. Depending on the gas content of the solutions fed to the xylem of the segments, their hydraulic conductivity was lowered by a freezing-thawing cycle by 20–50%. However, full recovery of hydraulic conductivity was found after about 2 days. Degassed solutions in contrast showed no impediment to flow after the same treatment. The results give evidence, firstly, that the harmful effect of freezing on functioning of water conducting elements is due to the formation of bubbles in xylem sap containing gas in solution, and secondly, that recovery from this impediment is possible in microporous vessels within a period of about 2 days.

Influence of climatic factors upon tree rings of Larix decidua and L. decidua × L. kaempferi from Pulawy, Poland

Abstract: Dendroclimatological techniques are used to assess the impact of climatic factors on tree-ring width of Larix decidua and L. decidua × L. kaempferi (= L. x eurolepis) growing in two experimental plots established in 1914 in south-west Poland. One plot included F1 progeny grown from seeds of an artificial crossing between European and Japanese larch. The other plot included progeny from maternal trees of European larch. Total ring width, earlywood width and latewood widths were dated, standardized and related to monthly climatic data using response function and stepwise multiple regression analyses. Wide rings in larch are associated with high precipitation in May–July, cool conditions in July–September of the preceding year, and cool dry conditions in August. Ring widths in L. x eurolepis are more dependent upon precipitation than ring widths in L. decidua. Latewood widths in L. x eurolepis are more dependent on high temperatures in June and July than latewood in L. decidua as well as total width and earlywood measurements. Variations in latewood were relatively independent of variations in earlywood and total wood. The variability of ring widths in these larches was greater than the variability reported for larches in many alpine sites and for other conifer species in some regions of North America.

A survey of seasonal bark proteins in eight temperate hardwoods

Abstract: Bark proteins of eight temperate hardwoods were analyzed by SDS-PAGE at monthly intervals to determine whether an accumulation of specific proteins, potential storage proteins, occurred in the fall at the time of leaf senescence. Storage proteins were identified as proteins that accumulated during the fall and were present in reduced amounts in the summer. Total protein levels were higher in the winter than in the summer in Fagus sylvatica, Fraxinus americana, Tilia americana, Alnus glulinosa, Betula papyrifera and Querus rubra, but not in Gleditsia triacanthos or Robinia pseudoacacia. Betula contained the most abundant storage protein, although in all species minor bands, which fluctuated seasonally, could be identified. With the exception of Alnus and Betula, results generally correlated with previous microscopy studies of these tree species, which showed varying amounts of protein storage vacuoles present in phloem parenchyma cells during the winter, but not during the summer.

Dormancy in peach ( Prunus persica L.) flower buds

Abstract: Peach buds (floral and vegetative) were periodically collected from midsummer until the spring flowering and sprouted under continuous light, 100% relative humidity and 20–25°C. Treatments with 200 ppm gibberellin A3 (GA3) or chilling (2–4°C for 30 days before planting) were applied. Vegetative buds showed well-defined phenological stages: pre-dormancy, “true dormancy”, and end of dormancy. Both GA3 and chilling treatments shortened the sprouting times of vegetative dormant buds close to those in predormancy. Isolated floral buds were irresponsive under all conditions and did not sprout even with the GA3 or chilling treatments. In a comparative study with buds immediately after collection anatomical analysis demonstrated that vegetative buds were almost completely developed by midsummer/early automn and remained in a resting state until the end of winter. Floral buds developed continuously over the same period. Both types of verticils began to differentiate in midsummer. Sepals and petals developed mainly in late summer, androecious floral parts developed throughout the resting period, while gynoecious floral parts showed differentiation in late winter. The flower was completely formed a few days prior to blossoming. Thus, in isolated peach buds fertile verticils are not sufficiently developed during the resting time to allow sprouting.

Fluoride effects on leaf cell ultrastructure of olive trees growing in the vicinity of the Aluminium Factory of Greece

Abstract: Leaves of olive trees growing in the vicinity of the Aluminium Factory of Greece were ultrastructurally investigated in order to determine any malformations caused by environmental air pollutants, especially hydrogen fluoride, in comparison with control samples and normal seasonal senescence. Estimation of some elements accumulated by these leaves showed that they contained high amounts of F and Al attributable to the operation of the nearby factory. The most seriously effected cell components were found to be the mesophyll chloroplasts that show a dilation of the intrathylakoid space, increase of the number of plastoglobuli, discoloration of plastoglobuli, accumulation of large starch grains and an overall disorganized appearance of the organelle. The nuclear crystalloid inclusions have unusual shapes, while the vacuoles contain a fibrillar/granular material that increases their electron density. It is concluded that the ultrastructural malformations are caused by a combination of environmental stresses and air pollutants.

Comparative studies on ectomycorrhizae synthesized with various in vitro techniques using Picea abies and two Hebeloma species

Abstract: Various in vitro synthesis techniques with Picea abies and two Hebeloma species showed that structures of the mantle and Hartig net of synthesized ectomycorrhizae within the given two fungus species are stable. However, thickness of mantle, and penetration depth and number of hyphal cell rows between cortical cells of the Hartig net are dependent on techniques and substrates. Porous glass balls as substrate in the Erlenmeyer technique seem to suppress or delay mantle and Hartig net formation. With the other techniques (growth pouch, open cuvette, Erlenmeyer with a vermiculite-peat moss mixture) development of the mantle is simultaneous with or shortly in advance of Hartig net formation. The ectomycorrhizae of the two tested Hebeloma species are similar and cannot be morphologically differentiated by the in vitro techniques used.

Small fruit problem in Citrus trees

Abstract: Physiological causes of the small fruit problem which occurs in certain trees of orange [Citrus sinensis (L.) Osbeck cv. Valencia] were investigated in terms of water relations and gas exchange of fruits during early fruit development as well as tree carbohydrate reserves. These data from cv. Valencia trees with and without a small fruit potential were compared with those of the large fruited cv. Navel. Neither fruit water potential nor fruit transpiration nor tree carbohydrate reserves appeared to be a cause of the small fruit. Yield records showed the small fruit to be assocaited with a large number of fruit per tree. However, fruits from cv. Valencia trees with a small fruit potential respired faster than either fruits of the same cultivar and size from trees without the physiological disorder or fruits of the same size of cv. Navel and also exceeded the dark respiration of the respective leaves. Hence, the small fruit problem in cv. Valencia was partly attributed to inefficient fruit photosynthesis, causing excessive respiration of each of a larger number of fruits compared to fruits of a tree of the same cultivar but without the physiological disorder. Fruits of cv. Valencia respired more in their 2 months longer lifetime on the tree relative to those of cv. Navel. It is concluded that orchard management methods will have to be investigated to balance the fruit load of the cv. Valencia tree utilizing the carbon available for fruit growth and to minimise stress during the early fruit development.

Nitrate reductase in needles, roots and trunk wood of spruce trees [ Picea abies (L.) Karst.]

Abstract: Nitrate reductase (EC 1.6.6.2) activity (NRA), as measured by an in vivo assay, is present in needle leaves and mycorrhizal fine root tips of adult Norway spruce [Picea abies (L.) Karst.] in at least equal amounts on a fresh weight basis, in both adult and 5-year-old trees. NRA could also be demonstrated in trunk wood of deroted trees after fertilization with 5 mM $${\text{NO}}_{{\text{3}}^{\text{ - }} }$$ , exhibiting a longitudinal profile in the trunk. Inducibility in needles can more efficiently be achieved by NO2 (100 μg·m-3) than by 5 mM nitrate, which is effective only in root-amputated trees. A remarkably high level of needle-NRA in unfertilized trees, which are characterized by a very low level of nitrate in the xylem sap, suggests that NRA in spruce needles may in part be constitutive. Organic-N is a major nitrogen source for the needles even in root-amputated trees, indicating pronounced exchange processes between ray parenchyma and trunk xylem, which in turn are modified by the nitrogen source fed to the trunk stump. Intact trees exhibit a very similar amino acid composition of the xylem sap, regardless of whether $${\text{NO}}_{{\text{3}}^{\text{ - }} }$$ or $${\text{NH}}_{{\text{4}}^{\text{ + }} }$$ has been fed. The amino acid pattern of the needles is not thrown out of balance by “flooding” with $${\text{NO}}_{{\text{3}}^{\text{ - }} }$$ and $${\text{NH}}_{{\text{4}}^{\text{ + }} }$$ , which occurs in fertilized derooted trees. This indicates a distinct potential for homoeostasis of nitrogen entrance-metabolism (i.e. NRA and glutamine synthetase activity) in the needles. In the ectomycorrhiza/fine root-system (EMC), marked differences in NRA were observed depending on root-tip diameter and along the longitudinal profile of the fine roots. EMC-nitrate reductase is strongly enhanced by $${\text{NO}}_{{\text{3}}^{\text{ - }} }$$ . Needle-NRA exhibits a circannual rhythm. An early summer maximum is followed by a December minimum. This activity pattern matches well the transitory increase of soluble nitrogen in spring and the total protein maximum in winter. In an indirect way assimilatory NRA may well contribute to nitrogen overfertilization (by consumption of NOX) as one possible cause of the contemporary decline of spruce populations.

Predicting tree diameter and height from above-ground biomass for four eucalypt species

Abstract: Previous work has suggested that tree stems are structured dimensionally to resist the forces to which they are subjected by the weight of the crown and the action of wind, snow and other loads on the crown This proposition has been used to develop allometric relationships relating diameter at breast height or height of individual trees growing in even-aged monoculture to their above-ground fresh biomass These models have practical application as estimators of tree diameters or heights from tree biomass as extensions of mechanistically based models of forest tree growth which predict tree biomasses The present work applied these models to Eucalyptus regnans F Muell, E delegatensis R Baker, E nitens (Deane: Maiden) Maiden and E grandis Hill ex Maiden trees, growing in plantation or regrowth stands, aged between 15 and 20 years, at eight geographically diverse sites extending from temperate to sub-tropical regions of Australia While the models held for the various species at the various sites, their parameter values differed significantly between sites and/or species This suggested there may be some inadequacy in the models However, the differences were small and it was found reasonable to fit single models across all species and sites for practical use in estimating diameter or height The errors about predicted values of height and diameter from these models were quantified The models were also found to estimate diameter or height with little loss of precision when dry biomass was used in place of fresh biomass

Protein-storing vacuoles in inner bark and leaves of softwoods

Abstract: The seasonal occurrence of protein-storage vacuoles in parenchyma cells of the inner bark and leaf tissues of seven softwood species was examined. Previously published results showed that these organelles often fill the phloem parenchyma cells of the inner bark tissues in overwintering hardwoods, whereas they are absent from this tissue during the summer. We hypothesize that the organelles are involved in the storage of reduced nitrogen during wintering, in a manner analogous to protein bodies of seeds. A survey of the phloem and cambial parenchyma tissues in six evergreen softwood species (Pinus strobus, P. sylvestris, Picea abies, P. glauca, Abies balsamea, and Thuja occidentalis) and in one deciduous softwood species (Larix decidua) was conducted. There was a large variation in the degree and timing of protein-storage vacuole formation between the individual genera and species. The organelles were not seen in summer samples of inner bark tissues of any of the genera or species examined. Protein-storage vacuoles were common in the bark tissues of Pinus, Abies and Thuja, occasionally seen in Picea, and rarely found in Larix during the winter. One-year-old leaves were also examined, since in all but Larix they are overwintering structures and can act as potential sites of nitrogen storage. Protein-storage vacuoles were present in Pinus and Thuja leaf tissue in both summer and winter, in Abies during winter only, and were absent from Picea leaf tissue at all times. These results indicate that the formation of protein-storage vacuoles prior to overwintering is not a ubiquitous phenomenon in softwoods.

Influence of needle loss, yellowing and mineral content on monoterpenes in the needles of Picea abies (L.) Karst.

Abstract: Monoterpenes in needles of Picea abies (L.) Karst. were studied to reveal whether or not the symptoms of forest decline observed in three mountain regions of South Germany (Bavaria) — needle loss and needle yellowing — are related to changes in the amounts of all or individual terpenes. The nutrient supply of the needles was examined in addition to the terpene concentrations, since the disease symptom montane yellowing is often associated with mineral deficiency. At two of the eight locations, trees exhibited Mg-deficiency, at one location K-deficiency was observed, and at another location the S-content of the needles indicated SO2-pollution. Using various statistical methods of analysis, no correlation was observed between the mineral element content of the needles, the percentage of needle loss and either the absolute or percentile terpene amounts stored within the needles. This finding is independent of needle age, date of sampling and terpene pattern. Concerning needle yellowing, the data show a tendency towards a reduction of the terpene concentrations in needles originating from branches with partly yellow needles compared to needles from exclusively green-needled branches. In spite of the fact that only 2-year-old and older needles show the disease symptom of yellowing, the terpene level is reduced even in still green, juvenile and 1-year-old needles. No terpene was found to be an indicator for early recognition of injury.

Occurrence of unidentified bodies that resemble “plastid initials” in poplar cells after breaking of dormancy in midwinter

Abstract: Electron-microscopic studies of plastids in cortical cells of poplar (Populus euramericana cv. gelrica) were carried out to examine whether any structural changes were initiated after breaking of dormancy in midwinter under non-growing conditions. After the breaking of dormancy, ultrastructural changes became evident and the profiles of plastids became heterogeneous. Organelles resembling the “plastid initials” proposed by Muhlenthaler and Frey-Wyssling in 1965 were frequently observed concomitant with changes in the plastid envelope. The formation of “plastid initials” appeared to be initiated by the formation of septa in pre-existing plastids. After this stage, narrow connections appeared between the “initials” and the parent plastids. Approximately 50 days after the breaking of dormancy in late March, further heterogeneity in the profiles of plastids was observed. At this stage, young plastids (plastids without starch granules) were frequently observed and the formation of “plastid initials” was hardly ever observed. These observations suggest that the “plastid initials” may be present for only a limited period in the cortical cells of the poplar and may be the precursors of the proplastids. Similar ultrastructural profiles were found in cortical cells of mulberry and in leaf buds of apple trees, suggesting that such changes in the ultrastructure of plastids are a general feature of perennials.

Nitrate levels affect the development of the black locust-Rhizobium symbiosis

Abstract: Experiments with black locust (Robinia pseudoacacia L.) seedlings grown under strictly controlled laboratory conditions indicated that the availability of nitrate has a marked impact on nitrogen fixation. When nitrate concentrations were very low, both nodulation and seedling growth were impaired, whereas nitrate concentrations high enough to promote plant growth strongly inhibited symbiotic nitrogen fixation. When nitrate was added to the growth medium after infection, nodulation and nitrogen fixation of the seedlings decreased. This effect was even more marked when nitrate was applied before infection with rhizobia. Higher nitrogen concentrations also reduced nodule number and nodule mass when applied simultaneously with the infecting bacteria. The contribution of symbiotic nitrogen fixation to black locust shoot mass by far exceeded its effects on shoot length and root mass. When nitrate availability was very low, specific nitrogen fixation (i. e. nitrogenase activity per nodule wet weight) was improved with increasing nitrogen supply, but rapidly decreased with higher nitrogen concentrations.

Quantitative and localized element analysis in cross-sections of spruce [ Picea abies (L.) Karst.] needles with different degrees of damage

Abstract: Proton-induced X-ray microanalysis (micro-PIXE) permits the simultaneous determination of the content and the distribution of elements with atomic numbers higher than Z = 13 in biological samples. This method was used to investigate element content and localization in cross-sections of 6-month-old spruce needles. It was possible to detect the elements silicon, phosphorus, sulphur, chlorine, potassium, calcium, manganese, iron and zinc in semithin (10 μm) sections of the needles. The localization of the cationic elements like potassium, calcium and manganese was determined in the one-dimensional line scan mode and in the two-dimensional raster scan mode. To demonstrate the usefulness of this method for forest decline research, element content and localization were compared in needles from two trees, which differed in their degree of damage. We were able to detect differences in the amount of cations and in their distribution inside the needles.