Macroscopic Features of Wind Damage to Leaves of Acer pseudoplatanus L. and Its Relationship with Season, Leaf Age, and Windspeed

Exposure to wind produces permanent abrasive damage to Acerpseudoplatanus L. leaves in the form of brown lesions, holes,distortions and tearing of the lamina. The zones of leaf thatare readily damaged change as the leaves expand and their topographyis altered. In the field, most damage was sustained early in the seasondespite the persistence of wind throughout the year. Wind tunnelstudies demonstrated that young expanding leaves were far moresusceptible to wind than mature leaves and that the percentagearea damaged increased linearly with windspeed. Acer pseudoplatanus L., sycamore, wind, leaf damage     

Senescence in Leaves of Acer pseudoplatanus L. and Parthenocissus tricuspidata Planch: 1. Changes in Some Leaf Constituents during Maturity and Senescence

Data are recorded of the changes in chlorophylls, carotene,sugar, shikimic acid, and anthocyanin in leaves of sycamore(Acer pseudoplatanus L.) and Virginia creeper (Parthenocissustricuspidata Planch.) during leaf maturity and senescence. InParthenocissus the losses of chlorophylls, carotene, sugar,and shikimic acid during senescence were closely correlated,and were inversely related to the accumulation of anthocyanin.The losses of chlorophylls, carotene, and sugar by Acer leaveswere also closely correlated. No evidence was found to supportthe suggestion that anthocyanin formation was caused by accumulationof sugar during senescence, but marked differences in shikimicacid content were found between leaves of Acer, which did notform anthocyanin, and Parthenocissus. which did. It is suggestedthat autumn senescence of these leaves involves the rapid senescenceof an increasing proportion of the leaf tissue during a periodof 80 days, and that measurements of the content of constituentsgive an estimate of the proportion of the leaf tissue whichhas senesced.     

Nuclear Replication Activity During Seed Development, Dormancy Breakage and Germination in Three Tree Species: Norway Maple (Acer platanoidesL.), Sycamore (Acer pseudoplatanusL.) and Cherry (Prunus aviumL.)

Flow cytometric analyses of nuclear DNA levels were carriedout during development, stratification and germination of dormantseeds from three tree species with contrasting characteristics.Norway maple (Acer platanoides) and sycamore (Acer pseudoplatanus)have orthodox (desiccation-tolerant) and recalcitrant (desiccation-sensitive)storage behaviours, respectively, and require only a periodof cold to break dormancy, whereas, orthodox cherry (Prunusavium) seeds require an initial warm period before cold stratificationto fully stimulate germination. Whole embryos and radicle tipsof both Norway maple and sycamore were found to have stablehigh levels of 4C DNA during the latter stages of developmentand both contained nuclei arrested at the 2C and 4C levels atmaturity. Mature cherry embryos had nuclei predominantly arrestedat the 2C level. This suggests that the acquisition of desiccationtolerance is not correlated with the arrest of the cell cycleat any particular nuclear DNA level. Neither DNA replicationin radicle cells nor germination occurred when seeds were maintainedmoist at a constant 20 °C. However, in the late stages ofcold treatment during stratification, nuclear DNA levels inradicle cells changed in advance of radicle emergence in theorthodox Norway maple and cherry, whereas in the recalcitrantsycamore, change was not recorded until after radicle emergence.These results show that DNA replication has potential use asan indicator of the progress of tree seeds through stratificationtreatments used to break some types of dormancy. The ways inwhich this indicator could be exploited for seed quality andperformance testing are discussed.Copyright 1998 Annals of BotanyCompany Norway maple,Acer platanoidesL., sycamore,Acer pseudoplatanusL., cherry,Prunus aviumL., DNA replication, flow cytometry, seed dormancy, stratification     

Multiple Metal Resistance and Co-resistance in Acer pseudoplatanus L. (Sycamore) Callus Cultures

In vitro growth of Acer pseudoplatanus L. (sycamore) callustissue derived from shoot-tip explants and screened on metal-enrichedmedia was studied in an attempt to identify resistance traitswhich may explain the survival of trees at metal-contaminatedsites. Copper and Cd-resistance traits were identified in celllines originating from trees at a site with a relatively recenthistory of severe contamination by these metals, and Cd- andZn-resistance were identified in cell lines originating frommature trees at a mining spoil site with a much longer historyof exposure to elevated concentrations of these metals. In Zn-resistantcell lines, co-resistance to Ni was also found, even thoughthis metal was not elevated at the study site. This is the firstreport of multiple resistance and co-resistance to metals occurringat the cellular level in trees. The mechanisms of the measuredresistance traits remain unclear, although there was evidenceof reduced Cu and Ni uptake by resistant cell lines. It is concludedthat facultative adaptations allowing acclimation to metal stressmay be particularly significant for survival of mature trees;induction of metal resistance probably occurs in vivo in treesat metal-contaminated sites.Copyright 1995, 1999 Academic Press Acer pseudoplatanus, sycamore, callus, heavy metals, metal resistance, trees     

Differences between Acer saccharum Leaves from Open and Wind-Protected Sites

Size-correlated variations of sugar maple (Acer saccharum L.)leaf anatomy and mechanical properties were determined for twosaplings (from open and wind protected sites) to examine theeffects of chronic wind-induced mechanical disturbance on leafsize, rigidity and flexibility. Based on a total sample of 78leaves, comparisons indicated that the mean size of the opensite leaves (n =37) was smaller in every measured respect comparedwith that of the closed site leaves (n =41). Open site leaveshad, on average, smaller lamina surface area, shorter and narrowerpetioles with a smaller volume fraction of lignified tissuesthan those from the closed site. Biomechanical comparisons alsoindicated that the petioles of open site leaves were significantlyless rigid and more flexible than the petioles of closed siteleaves. Despite differences in mean leaf size and petiolar rigidityand flexibility, allometric comparisons indicated the size-dependentvariations in leaf properties were continuous across the twosites. Also, the allocation of leaf biomass with respect tostem biomass along the lengths of the two saplings was statisticallyidentical and indistinguishable from an isometric relationship.However, the smaller diametered branches of the open site saplingbore smaller and fewer leaves with less stiff and rigid petiolesthan those of the closed site sapling. The differences betweenopen and closed site leaves are interpreted to be functionallyadaptive and to indicate that chronic mechanical disturbanceof developingAcer saccharum leaves prefigures mature leaf sizeand petiole properties that have the capacity to reduce winddrag. Results from petioles are contrasted with those of mechanicallydisturbed stems. Leaves; Acer saccharum ; biomechanics; wind-drag; allometry     

Interactive effects of exogenous growth regulators and artificial acid rain on cytokinins and gibberellins in maple seedlings

Vegetation experiments were conducted under greenhouse conditions in which long-term effects of simulated acid rain on the shoots, and short-term effects of acidified root medium on the roots of two maple species (Acer pseudoplatanus L. andAcer negundo L.) were studied. Both alternatives of the acidification stress were studied with respect to exogenous applications of auxins and gibberellins. Changes in seedling growth caused by acid rain were not marked, but changes in the levels of endogenous growth regulators were detected, both the long-term exposure ofAcer pseudoplatanus L. seedling shoots to acid rain and the short-term acidification of root environment resulted in enhanced cytokinin activity and in decreased gibberellin activity. But when A.pseudoplatanus L. seedlings were pretreated with gibberellins, their activity was further increased by increased acidity.Acer negundo L. seedlings responded to the acidification of their root environment with enhanced cytokinin activity only when pretreated with exogenous auxins. The differences in the responses ofA. pseudoplatanus L. and A.negundo L. to the acidification can be explained in terms of their distinct physiological properties, including changes recorded in chlorophyll content. The results obtained show that a pretreatment of maple seedlings with exogenous growth regulators can modify the effects of increased acidity in the environment on their physiological status as characterized by the level of endogenous cytokinins and gibberellins.     

Sample preservation for determination of organic compounds: microwave versus freeze-drying

In search of a reliable drying method, which might be used evenunder field conditions, microwave drying was compared to freeze-dryingof plant material. Leaves of Ananas comosus and Avicennia germinansas well as buds and phloem of Acer pseudoplatanus were usedand checked for one or more of the following substances: sugars,sugar alcohols, organic and amino acids, total nitrogen, andglycinebetaine. With most samples good agreement was achieved between the twodrying methods. Only in the case of the Ananas comosus leaves,which exhibited low pH and high water content, did appreciabledifferences occur in organic and amino acids. Besides that,sucrose was the compound most susceptible to alterations, whichwas especially evident when leaves of Sambucus nigra were driedin the two different compartments (condenser compartment, dryingbell jar) of the freeze-dryer in use. For Ananas comosus leaf samples it was shown that microwavingcan also be used prior to extraction of tissue sap. Key words: Microwave, freeze-drying, drying method, tissue sap, organic solutes     

Auxin in the Cambium and its Differentiating Derivatives

Cambium and differentiating xylem and phloem tissues from thetrunks of trees of Acer pseudoplatanus L., Fraxinus excelsiorL., and Populus tremula L. were extracted with ether and testedfor auxin, which was found on chromatograms of the acidic fractionat an Rf corresponding to that of indol-3yl-acetic acid in fivesolvent systems. In addition, small amounts of auxin with ahigher Rf in ammoniacal isopropanol were found in phloem samples.The amounts of auxin were greatest in xylem samples, less inthe cambium, and least in phloem. The differences, which cannotbe explained in terms of differential losses during extractionand purification, suggest that auxin is actually formed in differentiatingxylem tissue. The significance of these results is discussed.     

Cytokinins and the Growth Responses of Seedlings of Betula pendula Roth. and Acer pseudoplatanus L. to Nitrogen and Phosphorus Deficiency

Deficiencies in the supply of nitrogen and phosphorus broughtabout the cessation of shoot extension and the formation ofterminal resting buds in seedlings of Acer pseudoplatanus maintainedunder long days, whereas seedlings of Betula pendula maintainedunder the same conditions continued extension growth of themain axis over a long period, although they showed symptomsof nitrogen deficiency, including a reduced chlorophyll content.The endogenous cytokinin levels of the base/nucleoside fractionin leaves of B. pendula were significantly lower in the nitrogen-deficientplants than in the controls only 3 d after transfer to deficientconditions. Similar, though less marked, changes were observedin response to phosphorus deficiency. Changes in the levelsof cytokinin activity in the nucleotide fraction in responseto nitrogen deficiency were much less marked. No significantchanges in cytokinin levels of the base/nucleoside or nucleotidefractions could be detected in leaf material from seedlingsof A. pseudoplatanus, even after a nitrogen or phosphorus deficiencytreatment of 4 weeks. Application of exogenous benzyladenineto seedlings of B. pendula subjected to nitrogen deficiencyresulted in a rapid regreening and to outgrowth of inhibitedlateral buds after only 2 d.     

Osmotic Stress as a Pregrowth Procedure for Cryopreservation: 1. Growth and Ultrastructure of Sycamore and Soybean Cell Suspensions

Sycamore and soybean cell suspensions were subjected to osmoticstress by culturing for one passage in media supplemented with6 per cent mannitol or sorbitol. The effects on growth wereto reduce cell number and biomass (d. wt) production throughoutthe culture period by about 30 per cent. Ultrastructural studiesat the early exponential phase of culture growth indicated similarreductions in cell wall thickness in both species. Osmoticallystressed sycamore cells became less vacuolate, but no such changeoccurred in stressed soybean cells. Acer pseudoplatanus L., sycamore, Glycine max L. var. Biloxi, soybean, suspension culture cells, osmotic stress, growth, ultrastructure     

Modelling the Seasonal Nitrogen Partitioning in Young Sycamore (Acer pseudoplatanus) Trees in Relation to Nitrogen Supply

A model of nitrogen partitioning during the seasonal growthof sycamore (Acer pseudoplatanus) seedlings was developed andtested against data from trees grown with two contrasting levelsof nitrogen supply. The model considered each tissue type (roots,trunk, stems and leaves) as sources and sinks for nitrogen andused flow equations to simulate the dynamics of nitrogen partitioningduring a growing season, with increases in tissue dry matteras driving force variables. Withdrawal of nitrogen from leavesduring senescence was allocated back to other tissues assuminga linear decrease in leaf mass. The model was fitted to data from trees grown in sand culturewith 6·0 molN m^-3 (high N) supplied with the irrigation.Model parameters thus determined were used to predict nitrogenpartitioning in trees grown with 1·0 molN m^-3 (low N)in the same year, and for trees from both treatments given eitherhigh or low N during a second year. The model accurately predictedthe nitrogen content of roots and leaves and gave small errorsin the amount of nitrogen partitioned to stems. In contrast,the nitrogen content of the trunks were over-estimated due toa failure to simulate the decreased in nitrogen content foundat the start of the growing season. The ability of the modelto simulate nitrogen partitioning by changes in tissue dry matterin trees of varying size and nitrogen status is discussed andpossible modifications to model partitioning of trunk nitrogenmore accurately suggested.Copyright 1993, 1999 Academic Press Modelling, nitrogen partitioning, ¹⁵N supply, Acer pseudoplatanus (sycamore), young seedlings     

Differentiation in DNA fingerprinting among species of the genus Acer L. in Campania (Italy)

Abstract

Natural populations of species in the Acer genus occurring in Campania (southern Italy) were surveyed by screening seven microsatellite loci. Primer pairs for Acer pseudoplatanus L. microsatellite loci were analysed in six different species: Acer lobelii Ten., Acer campestre L., Acer pseudoplatanus L., Acer obtusatum W. et K., Acer neapolitanum Ten. and Acer monspessulanum L. The aim of the present study was to survey the genetic variability and genetic structure of natural populations of the Acer genus in Campania. The high degree of polymorphism observed in six different species of Acer makes these markers useful for investigating genetic variation at various spatial scales, and for the analysis of gene flow and of the mating system.     

Osmotic Stress as a Pregrowth Procedure for Cryopreservation 3. Cryobiology of Sycamore and Soybean Cell Suspensions

Aspects of low temperature behaviour of sycamore and soybeancell suspensions were studied following pregrowth in the presenceof 6 per cent mannitol or sorbitol. Sycamore cells exhibitedcontraction of the cell wall following treatment with 2 m cryoprotectantand improved recovery after cryopreservative procedures. Theseresponses were not paralleled by pregrown soybean cells. Studieson the behaviour of the cells in the presence of extracellularice, using cryomicroscopy, and in the absence of extracellularice, using differential scanning calorimetry (DSC), were unableto identify any alteration in the low temperature response ofpregrown sycamore cells which could readily explain their improvedfreeze tolerance. Acer pseudoplatanus L., sycamore, Glycine max L. var. Biloxi, soybean, suspension culture cells, osmotic stress, undercooling, cryopreservation, cryomicroscopy     

Acclimation of Trees to Pollution Stress: Cellular Metal Tolerance Traits

Cell suspension cultures were established from shoot explantsof mature trees of Acer pseudoplatanus L. (sycamore) at a sitecontaminated by aerial deposition of copper and cadmium frommetal processing industry, and from the same species at uncontaminatedsites. The responses of cell cultures to elevated metal concentrationsin growth media differed markedly according to site of origin.Both Cu and Cd, applied singly at concentrations of 10–15mg l^–1, inhibited growth and were toxic to cultures originatingfrom the uncontaminated sites, but not to cultures from thecontaminated site. This metal tolerance trait in the culturesfrom the contaminated site was stable through repeated sub-culturing.It could also be induced in one culture originating from thereference uncontaminated site, by gradually exposing the cultureto increasing concentrations of Cu. A reduced level of metalremoval from the media was found in tolerant cultures, comparedto non-tolerant cultures. The results of these experiments demonstratethe occurrence of an alteration of gene expression in responseto pollution stress, suggesting that metal tolerance may beinduced within shoot meristems in vivo. It also represents thefirst example of non-mycorrhizal adaptation to metal toxicityidentified in woody plants. Trees, pollution, metal tolerance, acclimation, plant tissue culture, Acer pseudoplaianus L., sycamore     

Studies of the Growth in Culture of Plant Cells

Mitochondria have been isolated from sycamore cells (Acer pseudoplatanusL.) grown in suspension culture, and resemble those of otherplant tissues. Malate, succinate, and NADH are oxidized withrespiratory control. The respiration is partially inhibitedby antimycin A and KCN, but not by amytal and rotenone. Octylguanidine,oligomycin, and uncouplers all affect the coupled respiration. The proportion of the respiration resistant to KCN was foundto change during the life of the culture, being greatest duringthe lag phase and least during the linear phase. The relationshipof these changes in the electron transport pathways to the changingdemand of the culture for phosphorylated and other intermediatesis discussed.     

Frequency of inversions affects senescence phenology of Acer pseudoplatanus and Fagus sylvatica

In mountainous regions, inversion situations with cold-air pools in the valleys occur frequently, especially in fall and winter. With the accumulation of inversion days, trees in lower elevations experience lower temperature sums than those in middle elevations. In a two-year observational study, deciduous trees, such as Acer pseudoplatanus and Fagus sylvatica, on altitudinal transects responded in their fall leaf senescence phenology. Phenological phases were advanced and senescence duration was shortened by the cold temperatures in the valley. This effect was more distinct for late phases than for early phases since they experienced more inversion days. The higher the inversion frequency, the stronger the signal was. Acer pseudoplatanus proved to be more sensitive to cold temperatures compared to Fagus sylvatica. We conclude that cold-air pools have a considerable impact on the vegetation period of deciduous trees. Considering this effect, trees in the mid hillside slopes gain advantages compared to lower elevations. Our findings will help to improve knowledge about ecological drivers and responses in mountainous forest ecosystems.     

Acclimation to Drought in Acer pseudoplatanus L. (Sycamore) Seedlings

A glasshouse experiment was conducted with well-watered andwater-stressed seedlings of sycamore (Acer pseudoplatanus L.)grown in soil columns. Water was withheld when the seedlingswere 82-d-old. Effects of soil drying on stomatal behaviour,water relations, xylem cavitation, and growth of leaves androots were evaluated. Stomatal conductance declined well before any observable changein bulk leaf water potentials, and was correlated with soilwater status. At seven weeks, osmotic potential had declinedby 0·51 MPa and 0·44 MPa at full and zero turgor,respectively. Drought significantly increased both bulk elasticmodulus and leaf dry weight to turgid weight ratio of water-stressedplants. Drought had no effect on relative water content at zeroturgor. Water cavitation in the xylem was detected as ultrasonic acousticemissions (AE). Water-stressed plants displayed significantlyhigher rates of AE than well-watered plants. Maximum rate ofAE coincided with the minimum level of stomatal conductanceand apparent rehydration of the leaves. Drought caused changes in the root distribution profile andit increased the root weight. The increase in root weight wasmainly due to a substantial shift in assimilates allocated infavour of roots with total biomass being unaffected. Leaf growthwas maintained for six weeks without any significant declinein expansion rate. However, the development of severe waterstress reduced both leaf production and expansion.     

Characterization of microsatellite markers in sycamore (Acer pseudoplatanus L.)

Sycamore (Acer pseudoplatanus L.) is a tetraploid European hardwood tree species. The reproduction system of the insect‐pollinated trees and patterns of genetic variation are largely unknown. We isolated and characterized eight polymorphic microsatellite markers for Acer pseudoplatanus L. The high degree of polymorphism observed at these markers makes them useful to observe genetic variation patterns at various spatial scales and to analyse gene flow and the mating system. Primers developed for the amplification of microsatellites in A. pseudoplatanus were tested for 21 different species of genus Acer. Amplification products of the expected size were obtained in most cases.     

Studies on the Growth in Culture of Plant Cells: XI. THE INFLUENCE OF SHAKING RATE ON THE GROWTH OF SUSPENSION CULTUEES

The influence of shaking rates (expressed as revolutions permin) on orbital shaking platforms (1 in (2.54 cm) diam. rotarymotion) on the growth of cell suspension cultures of Acer pseudoplatanusL. and Atropa belladonna cultivar lutea Döll are described.By following cell growth and respiration and the levels of oxygenand carbon dioxide in the media during the progress of incubationit is concluded that the reduction of growth at sub-optimalshaking rates is not due to oxygen deficiency or toxic accumulationof carbon dioxide. The growth of the Atropa cell suspensionin ‘closed systems’ has been studied by the developmentof modified culture vessels and evidence obtained that the reducedgrowth in the systems is due to the formation by the culturesof an unidentified volatile growth inhibitor and not to eitheroxygen depletion or toxic accumulation of either carbon dioxideor ethylene. It is suggested that the reduced growth in ‘opensystems’ cultures at sub-optimal shaking speeds is eitherdue to retention of this volatile inhibitor or to restrictionof nutrient uptake by the existence of a stationary liquid-phaseboundary to the cells.     

The Effect of Wind on Grasses II. Mechanical Damage in Festuca arundinacea Schreb

After a period of exposure to wind in a wind tunnel, two aspectsof the resulting mechanical damage in Festuca arundinacea Schreb.var. S170 were examined. These were the frequency of occurrenceof transverse fold lines and the microscopic nature of leafabrasion marks. Transverse fold lines were found to be of morefrequent occurrence in wind-exposed plants. A stereoscan electronmicroscope was used to show the severe damage to the leaf surfacethat can result from leaves rubbing over each other. Some possibleconsequences of such damage are discussed.