Growth pattern and age determination for Cecropia sciadophylla (Urticaceae)

Cecropia species, ranging from Mexico to northern Argentina and the West Indies, are pioneer trees that colonize cleared areas with high light. To determine their ages to help pinpoint the date of the area's disturbance, we need to understand their developmental and architectural changes over time. The simple architecture of Cecropia conforms to the model of Rauh; that is, it has orthotropic axes with lateral flowering and rhythmic branching. The axes are made of a succession of nodes and internodes whose length and associated lateral productions remain measurable for years. Thus, by describing the tree trunk node by node, we can depict the sequence of events involved in tree development. For 25 trees of C. sciadophylla, from two stations in French Guiana and Colombia, we recorded internode length and any presence of branches, and flowers for each node. Using autocorrelation coefficients, we found a high periodicity in flowering and branching, with inflorescences at every 25 nodes, stages of branches spaced by a multiple of 25 nodes, and alternation of long and short nodes every 25 nodes. Considering that flowering is annual for many Cecropia species, the main conclusion of this work is that C. sciadophylla has strong annual growth, branching, and flowering rhythms. In addition, the age of the tree can be estimated retrospectively by observing its adult morphology.     

Territorial aggressiveness on the arboreal ant Azteca alfari by Camponotus blandus in French Guiana due to behavioural constraints

This study reports new information on interactions between two sympatric ant species, the plant-ant Azteca alfari (Dolichoderinae) living in association with the myrmecophyte Cecropia obtusa (Cecropiaceae) and Camponotus blandus (Formicinae), a ground-nesting, arboreal-foraging species. Workers of A. alfari forage only on the foliage and the upper parts of the trunk of their host Cecropia, while C. blandus nests in the ground but frequently forages and patrols pioneer tree foliage, including Cecropia. The activity pattern of A. alfari and the number of C. blandus on Cecropia obtusa was monitored hourly during a two-day period in a disturbed area in French Guiana. The maximum activity of C. blandus occurred between 8:30 and 12:30, at which time A. alfari had retreated within the domatia and were least present on the trunks. Even though aggressive confrontations were observed, C. blandus workers often initiate confrontations but do not prey on A. alfari nor exploit food bodies produced by Cecropia, the principal food source of A. alfari. Hence hostility appears to be the result of territoriality. Differences in their foraging rhythms are proposed as promoting resource and territory partitioning in this ant assemblage. To cite this article: M. McClure et al., C. R. Biologies 331 (2008).     

Node-specific branching and heterochronic changes underlie population-level differences in Mimulus guttatus (Phrymaceae) shoot architecture

? Premise of the study: Shoot architecture is a fundamentally developmental aspect of plant biology with implications for plant form, function, reproduction, and life history evolution. Mimulus guttatus is morphologically diverse and becoming a model for evolutionary biology. Shoot architecture, however, has never been studied from a developmental perspective in M. guttatus. ? Methods: We examined the development of branches and flowers in plants from two locally adapted populations of M. guttatus with contrasting flowering times, life histories, and branch numbers. We planted second-generation seed in growth chambers to control for maternal and environmental effects. ? Key results: Most branches occurred at nodes one and two of the main axis. Onset of branching occurred earlier and at a greater frequency in perennials than in annuals. In perennials, almost all flowers occurred at the fifth or more distal nodes. In annuals, most flowers occurred at the third and more distal nodes. Accessory axillary meristems and higher-order branching did not influence shoot architecture. ? Conclusions: We found no evidence for trade-offs between flowers and branches because axillary meristem number was not limiting: a large number of meristems remained quiescent. If, however, quiescence is a component of meristem allocation strategy, then meristems may be limited despite presence of quiescent meristems. At the two basalmost nodes, branch number was determined by mechanisms governing either meristem initiation or outgrowth, rather than flowering vs. branching. At the third and more distal nodes, heterochronic processes contributed to flowering time and branch number differences between populations.     

A simulation model of the three-dimensional architecture of the maize root system

In order to study the nutrient and water uptake of rootsin situ, we need a quantitative three-dimensional dynamic model of the root system architecture. The present model takes into account current observations on the morphogenesis of the maize root system. It describes the root system as a set of root axes, characterised by their orders and their inter-node of origin. The evolution of the simulated pattern is achieved by three processes, occuring at each time step: emission of new primary root axes from the shoot, growth and branching of existing root axes. The elongation of an axis depends on its order, inter-node and local growing conditions. Branches appear acropetally at a specified distance from the apex and from former branches, along ranks facing xylem poles, with a branching angle specific to their order and inter-node. From the three-dimensional branched patterns simulated by the model, various outputs, such as root profiles or cross-section maps can be computed, compared to observed data and used as inputs in uptake models. A number of examples of such possible outputs are presented.     

Clarifying the effects of dwarfing rootstock on vegetative and reproductive growth during tree development: a study on apple trees

BACKGROUND AND AIMS: Despite the widespread use of dwarfing rootstocks in the fruit-tree industry, their impact on tree architectural development and possible role in the within-tree balance between growth and flowering are still poorly understood, in particular during the early years of growth. The present study addressed this question in apple trees, through a detailed analysis of shoot populations, i.e. both vegetative and flowering shoots, during tree development. METHODS: Architectural databases were constructed for trees of two cultivars that were either own-rooted or grafted on dwarfing rootstock. Within-tree shoot demographics and annual shoot characteristics, i.e. their dimensions, number of laterals and flowering, were observed from the first to the fifth year of growth and compared among scion/root system combinations. KEY RESULTS: Differences in axis demographics appeared among scion/root system combinations after the second year of growth. Differences were found (a) in the number of long axes and (b) the number of medium axes. Dwarfing rootstock reduced the total number of axes developed in a tree, and this reduction resulted from proportionally more medium axes and spurs than long axes. The life span of spurs was also shortened. These phenomena appeared after an increase in flowering that started in the second year of growth and involved both axillary and terminal positions. Flowering regularity was also increased in grafted trees. CONCLUSIONS: These results confirm that the number of long shoots and flowering potential depend on the cultivar. They indicate that tree architectural plasticity in response to its root system mainly derives from the number of medium shoots developed and follows priorities within the whole tree axis population. There was also evidence for dwarfing rootstock involvement in adjusting the flowering abundance and that differences in flowering occurrence take precedence over those regarding vegetative growth during tree development.     

Phylogenetic dating with confidence intervals using mean path lengths

The mean path length (MPL) method, a simple method for dating nodes in a phylogenetic tree, is presented. For small trees the age estimates and corresponding confidence intervals, calibrated with fossil data, can be calculated by hand, and for larger trees a computer program gives the results instantaneously (a Pascal program is available upon request). Necessary input data are a rooted phylogenetic tree with edge lengths (internode lengths) approximately corresponding to the number of substitutions between the nodes. Given this, the MPL method produces relative age estimates with confidence intervals for all nodes of the tree. With the age of one or several nodes of the tree being known from reference fossils, the relative age estimates induce absolute age estimates and confidence intervals of the nodes of the tree. The MPL method relies on the assumptions that substitutions occur randomly and independently in different sites in the DNA sequence and that the substitution rates are approximately constant in time, i.e., assuming a molecular clock. A method is presented for identification of the nodes in the tree at which significant deviations from the clock assumption occur, such that dating may be done using different rates in different parts of the tree. The MPL method is illustrated with the Liliales, a group of monocot flowering plants.     

Influence of nitrogen availability on shoot development in young peach trees [Prunus persica (L.) Batsch]

It is commonly stated that nitrogen (N) influences biomass accumulation in plants. For trees, however, a precise characterisation of shoot response to N and its impact on architecture is lacking. We attempted to study on the phytomer scale the effects of N limitation on shoot growth components, i.e. leaf emergence rate, final internode length and branching on the main and secondary axes of 1-year-old peach trees [Prunus persica (L.) Batsch]. Trees were grown on recycled nutrient solutions in which N concentration was restored once a week. We used two hydroponic set-ups in which weekly N availability, i.e. amount of N per tree, differed being either low (N1) or high (N2). Net N availability was defined weekly as the relative amount of N remaining in each set-up before solution replenishment. It declined with time and three periods of contrasting net N availability were identified. During these periods, leaf emergence rate and final internode length were similar on the main axis of N1 and N2 trees, so too was the distribution of secondary axes along the main axis. Secondary axes responded to N limitation by decreasing their growth components according to their position along the main axis. Differences were most important for basal secondary axes. Leaf emergence rate and final internode length responded similarly to N availability depending on axis order and position in the tree. It was concluded that N availability, particularly during the period of maximum growth of axes, influenced the shoot growth components and thus tree architecture.     

Factors controlling resource allocation in mountain birch

We present a comprehensive analysis of factors affecting resource allocation and crown formation in a subarctic birch tree, Betula pubescens ssp. czerepanovii (Orlova) Hämet-Ahti. Using biomass measurements and digitized data on tree architecture, we investigated several hypotheses on various factors that may modify plant growth. We also analyzed the extent to which different mechanisms operate at different scales, ranging from individual shoots to the whole branches or trees. Different factors affected allocation at different levels of organization. Stem age had a minor effect, suggesting that similar control mechanisms operate at all stages of development. Fates of individual shoots were affected by their local growing conditions as indicated, for example, by the dependence of long shoot production on light. Buds formed in the current long shoots were likely to become new long shoots. In the innermost crown parts, radial growth had priority compared to long shoot production. Elongation of individual long shoots was controlled by two conflicting factors. Long distance from the roots suppressed growth, probably indicating costs associated with resource transportation, whereas a high level of light augmented growth. In contrast, growth of entire branches was not so clearly related to the availability of resources, but showed limitation due to allometric scaling. This set a relationship between the maximum long shoot number and the overall branch size, and may indicate allometric constraints to the way a tree is constructed. Strict allometric relationships existed also between other structural traits of mountain birch, most of them similar at all levels of branching hierarchy. However, despite the upper level restrictions set by allometry, source-sink interactions and localized responses of individual shoots operated as local processes that directed allocation towards the most favourable positions. This may be a mechanism for achieving efficient tree architecture in terms of resource intake and costs of transportation.     

Fruit set in Styrax obassia (Styracaceae): the effect of light availability, display size, and local floral density

Maternal reproductive success was examined in Styrax obassia (Styracaceae), a bumble-bee pollinated mass-flowering tree in a cool-temperate deciduous forest in northern Japan. The effects of flower number on the success of individual flowers at three levels (inflorescence, individual, and population) were considered. During 1995 and 1996, variations in size, light availability to branches, floral display size, and fruit set were monitored in 37 out of 211 individual S. obassia trees in a 4-ha forest plot. In addition, the locations of the 211 trees in this plot were mapped and the number of inflorescences in each tree was counted. A multiple regression analysis showed that flower number per inflorescence and inflorescence number per individual had negative effects on fruit set, and inflorescence number of aggregated clumps of flowering trees, tree size, and light resource had positive effects on fruit set although significant level were marginal. It is concluded that pollinator attraction may occur not at the individual tree level, but at the level of a clump of flowering trees. It is also suggested that geitonogamy increased with inflorescence number of tree and inflorescence size and that resource limitation was related to the light condition and variation of tree size.     

Tree Species Composition, Structure, and Aboveground Wood Biomass of a Riparian Forest of the Lower Miranda River, Southern Pantanal, Brazil

The aboveground wood biomass (AWB) of tropical forests plays an important role in the global carbon cycle, and local AWB estimates provide essential data that enable the extrapolation of biomass stocks to ecosystem or biome-wide carbon cycle modelling. Few AWB estimates exist in Neotropical freshwater floodplains, where tree species distribution and forest structure depend on the height and duration of periodic inundations. We investigated tree species composition, forest structure, wood specific gravity, and AWB of trees ≥10 cm dbh in 16 plots totalling an area of 1 ha in a seasonally inundated riparian forest of the lower Miranda River, southern Pantanal, Brazil. The 443 tree individuals belonged to 46 species. Four species (Inga vera, Ocotea suaveolens, Tabebuia heptaphylla and Cecropia pachystachya) comprised more than 50% of the Total Importance Values (TIV), and floristic similarities between the plots averaged 38%. Although we detected an overall increase in species diversity correlated with decreasing flood levels, the most important tree species had almost identical distribution patterns along the flooding gradient. The stand basal area per plot (±?s.d.) amounted to 3.0?±?1.1 m² (47.8?±?18.1 m²/ha), and the tree heights averaged 10.9?±?1.4 m. Multiplying the individual basal areas by individual tree heights and a form factor of 0.6, we estimated the aboveground wood volume (AWV) for each individual, and for each plot (24.4?±?11.7 m³, 391.1?±?188 m³/ha). Wood specific gravity (SG) varied between 0.39 g/cm³ (Cecropia pachystachya) and 0.87 g/cm³ (Tabebuia heptaphylla), with a stand level average of 0.63?±?0.12 g/cm³. Multiplying the individual AWV with species SG, we estimated the plot AWB to be 16.2?±?6.4 Mg (259.4?±?102 Mg/ha). This value is comparable to that reported for late-successional forest stands of Amazonian floodplain forests, and it is close to the worldwide tropical average AWB. Because tree heights in the present forest were comparatively low when compared to other Neotropical forests, we found that resprouting of stems accounted for comparatively high basal areas. We argue that stem resprouting is an adaptation of tree species originating in non-flooded Cerrado to the seasonal inundations of riparian forests.     

Variation in crown light utilization characteristics among tropical canopy trees

BACKGROUND AND AIMS: Light extinction through crowns of canopy trees determines light availability at lower levels within forests. The goal of this paper is the exploration of foliage distribution and light extinction in crowns of five canopy tree species in relation to their shoot architecture, leaf traits (mean leaf angle, life span, photosynthetic characteristics) and successional status (from pioneers to persistent). METHODS: Light extinction was examined at three hierarchical levels of foliage organization, the whole crown, the outermost canopy and the individual shoots, in a tropical moist forest with direct canopy access with a tower crane. Photon flux density and cumulative leaf area index (LAI) were measured at intervals of 0.25-1 m along multiple vertical transects through three to five mature tree crowns of each species to estimate light extinction coefficients (K). RESULTS: Cecropia longipes, a pioneer species with the shortest leaf life span, had crown LAI <0.5. Among the remaining four species, crown LAI ranged from 2 to 8, and species with orthotropic terminal shoots exhibited lower light extinction coefficients (0.35) than those with plagiotropic shoots (0.53-0.80). Within each type, later successional species exhibited greater maximum LAI and total light extinction. A dense layer of leaves at the outermost crown of a late successional species resulted in an average light extinction of 61% within 0.5 m from the surface. In late successional species, leaf position within individual shoots does not predict the light availability at the individual leaf surface, which may explain their slow decline of photosynthetic capacity with leaf age and weak differentiation of sun and shade leaves. CONCLUSION: Later-successional tree crowns, especially those with orthotropic branches, exhibit lower light extinction coefficients, but greater total LAI and total light extinction, which contribute to their efficient use of light and competitive dominance.     

Caterpillars and fungal pathogens: two co-occurring parasites of an ant-plant mutualism

In mutualisms, each interacting species obtains resources from its partner that it would obtain less efficiently if alone, and so derives a net fitness benefit. In exchange for shelter (domatia) and food, mutualistic plant-ants protect their host myrmecophytes from herbivores, encroaching vines and fungal pathogens. Although selective filters enable myrmecophytes to host those ant species most favorable to their fitness, some insects can by-pass these filters, exploiting the rewards supplied whilst providing nothing in return. This is the case in French Guiana for Cecropia obtusa (Cecropiaceae) as Pseudocabima guianalis caterpillars (Lepidoptera, Pyralidae) can colonize saplings before the installation of their mutualistic Azteca ants. The caterpillars shelter in the domatia and feed on food bodies (FBs) whose production increases as a result. They delay colonization by ants by weaving a silk shield above the youngest trichilium, where the FBs are produced, blocking access to them. This probable temporal priority effect also allows female moths to lay new eggs on trees that already shelter caterpillars, and so to occupy the niche longer and exploit Cecropia resources before colonization by ants. However, once incipient ant colonies are able to develop, they prevent further colonization by the caterpillars. Although no higher herbivory rates were noted, these caterpillars are ineffective in protecting their host trees from a pathogenic fungus, Fusarium moniliforme (Deuteromycetes), that develops on the trichilium in the absence of mutualistic ants. Therefore, the Cecropia treelets can be parasitized by two often overlooked species: the caterpillars that shelter in the domatia and feed on FBs, delaying colonization by mutualistic ants, and the fungal pathogen that develops on old trichilia. The cost of greater FB production plus the presence of the pathogenic fungus likely affect tree growth.     

Non‐continuous reproductive phenology of animal‐dispersed species in young forest restoration plantings

Tree species that produce resources for fauna are recommended for forest restoration plantings to attract pollinators and seed dispersers; however, information regarding the flowering and fruiting of these species during early growth stages is scarce. We evaluated the reproductive phenology of animal‐dispersed tree species widely used in Atlantic Forest restoration. We marked 16 animal‐dispersed tree species in 3‐ to 8‐year‐old forest restoration plantings in Itu‐São Paulo, southeast Brazil. We noted the age of the first reproductive event, flowering and fruiting seasonality, percentage of trees that reached reproductive stages, and intensity of bud, flower, and fruit production for each species. Flowering and fruiting are seasonal for most species; only two, Cecropia pachystachya and Ficus guaranitica, exhibited continuous flowering and fruiting throughout the year; we also identified Schinus terebinthifolia and Dendropanax cuneatus fruiting in the dry season during resource scarcity. Therefore, we recommend all as framework species, that is, species that are animal‐dispersed with early flowering and fruiting potential, for forest restoration. Further, we recommend identifying and planting similar animal‐dispersed tree species that produce fruits constantly or in the dry season to maximize fauna resource availability throughout the year in tropical forest restoration plantings. Abstract in Portuguese is available with online material     

Dynamics of heterorhizic root systems: protoxylem groups within the fine-root system of Chamaecyparis obtusa

To understand the physiology of fine-root functions in relation to soil organic sources, the heterogeneity of individual root functions within a fine-root system requires investigation. Here the heterogeneous dynamics within fine-root systems are reported. The fine roots of Chamaecyparis obtusa were sampled using a sequential ingrowth core method over 2 yr. After color categorization, roots were classified into protoxylem groups from anatomical observations. The root lengths with diarch and triarch groups fluctuated seasonally, whereas the tetrarch root length increased. The percentage of secondary root mortality to total mortality increased with increasing amounts of protoxylem. The carbon : nitrogen ratio indicated that the decomposability of primary roots might be greater than that of secondary roots. The position of diarch roots was mostly apical, whereas tetrarch roots tended to be distributed in basal positions within the root architecture. We demonstrate the heterogeneous dynamics within a fine-root system of C. obtusa. Fine-root heterogeneity should affect soil C dynamics. This heterogeneity is determined by the branching position within the root architecture.     

Molecular biology of feather morphogenesis: a testable model for evo-devo research

Darwin's theory describes the principles that are responsible for evolutionary change of organisms and their attributes. The actual mechanisms, however, need to be studied for each species and each organ separately. Here we have investigated the mechanisms underlying these principles in the avian feather. Feathers comprise one of the most complex and diverse epidermal organs as demonstrated by their shape, size, patterned arrangement and pigmentation. Variations can occur at several steps along each level of organization, leading to highly diverse forms and functions. Feathers develop gradually during ontogeny through a series of steps that may correspond to the evolutionary steps that were taken during the phylogeny from a reptilian ancestor to birds. These developmental steps include 1) the formation of feather tract fields on the skin surfaces; 2) periodic patterning of the individual feather primordia within the feather tract fields; 3) feather bud morphogenesis establishing anterio-posterior (along the cranio-caudal axis) and proximo-distal axes; 4) branching morphogenesis to create the rachis, barbs and barbules within a feather bud; and 5) gradual modulations of these basic morphological parameters within a single feather or across a feather tract. Thus, possibilities for variation in form and function of feathers occur at every developmental step. In this paper, principles guiding feather tract formation, distributions of individual feathers within the tracts and variations in feather forms are discussed at a cellular and molecular level.     

Application of the Functional-Structural Tree Model LIGNUM to Sugar Maple Saplings (Acer saccharum Marsh) Growing in Forest Gaps

LIGNUM is a functional-structural model that represents a treeusing four modelling units which closely resemble the real structureof trees: tree segments, tree axes, branching points and buds.Metabolic processes are explicitly related to the structuralunits in which they take place. Here we adapt earlier versionsof LIGNUM designed to model growth of conifers for use withbroad-leaved trees. Two primary changes are involved. First,the tree segment for broad-leaved trees consists of enclosedcylinders of heartwood, sapwood and bark. Leaves consistingof petioles and blades are attached to the segments. Secondly,axillary buds and rules governing their dormancy are includedin the model. This modified version of LIGNUM is used to simulatethe growth and form of sugar maple saplings in forest gaps.The annual growth of the model tree is driven by net productionafter respiration losses are taken into account. The productionrate of each leaf depends on the amount of photosyntheticallyactive radiation it receives. The radiation regime is trackedexplicitly in different parts of the tree crown using a modelof mutual shading of the leaves. Forest gaps are representedby changing the radiation intensity in different parts of themodel sky. This version of LIGNUM modified for use with broad-leaf,deciduous trees and parameterized for sugar maple, yields goodsimulations of growth and form in saplings from different forestgap environments. Copyright 2001 Annals of Botany Company LIGNUM, functional-structural tree model, tree architecture, sugar maple, modelling growth and form     

Branching Principles Governing the Architecture of Cornus kousa (Cornaceae)

The complex structure of the crown of Cornus kousa, generallyfive-forked in vegetative branching and two-forked in reproductivebranching, is analysed quantitatively and described by two basicbranching principles: decussate phyllotaxy and the resettingrule for planes of branching. Most Cornus species have opposite,decussate phyllotaxis. The leaf pair (with axillary buds) definesthe branching plane of a node. Because of regular phyllotaxis,the fundamental branching pattern is that every branching planealong an axis is perpendicular to the preceding one. However,the first node of a lateral horizontal shoot always has a horizontalbranching plane; we term this the resetting rule. We observedthat resetting occurs when the first nodes initiated in thevertical plane are repositioned by a twisting of their firstinternodes. All later nodes alternate directions, i.e. showusual decussate alternation. Foliage leaf nodes usually producethree-forked branchings. When vegetative winter buds are formed,a foliar node and adjacent scale leaf node produce a five-forkedbranching. When reproductive winter buds with a terminal inflorescenceare formed, the last foliar node and two adjacent scale leafnodes can produce a variety of branchings but usually producean equal two-forked branching. To understand better the architecturein C. kousa, we contrast it with C. capitata which does notproduce buds with scale leaves and whose vegetative nodes areclearly separated. Copyright 1999 Annals of Botany Company Branching pattern, Cornaceae, Cornus kousa, decussate branching, dogwood, Japanese strawberry tree, tree architecture, tree geometry.     

Modelling branching patterns on 1-year-old trunks of six apple cultivars

The structure resulting from branching on 1-year-old apple tree trunks was analysed in a set of apple cultivars with diverse branching and fruiting habits. Four different lateral types borne on successive nodes were observed when vegetative and flowering fates, as well as sylleptic and proleptic branching, were taken into account. The location and grouping of lateral types along the trunk were analysed for all cultivars, but are detailed for one cultivar only. This cultivar showed a succession of zones, each zone being characterized by its composition of lateral types. Statistical models-hidden semi-Markov chains-were built to take this structure into account and to characterize the cultivar's specific branching pattern. The models showed that most of the branching zones had a similar location in the different cultivars, even though zone composition and zone length differed among cultivars. On a more detailed scale, the nodes bearing a lateral, regardless of its type, were frequently followed by latent buds. The validity of the models and their biological interpretation are discussed with respect to parent shoot dynamics, hormonal gradients and competition between neighbouring buds.     

A mechanical analysis of the relationship between free oscillations of Pinus pinaster Ait. saplings and their aerial architecture

The aim of this study was to investigate the influence of aerial architecture on the dynamic characteristics of young maritime pines (Pinus pinaster Ait.) using a mechanistic approach. For this purpose, three 4-year-old saplings with prominent differences in their branching patterns were submitted to free oscillation tests. The tests were carried out with different methods and directions of mechanical loading in order to initiate the movement of each sapling. The oscillations of the different architectural elements, i.e. stem and branches of different topological order, were measured with inclinometers and strain gauges fixed to saplings. Successive pruning of the architectural elements was carried out to evaluate their relative influence on the dynamic characteristics of the trees. The aerial systems were digitized before the mechanical tests in order to use 3D visualization techniques and to make architectural analyses of the crown structure. Two distinct modes of deformation were detected during free oscillations. The natural swaying frequency ranged from 0.6-0.8 Hz for the saplings tested at the same period of the year. The frequency variations were partly explained by the morphological differences of the experimental subjects. The motions of the axes were found to depend on their topology, i.e. the movement of the axes of a given branching order was forced by the movement of their respective bearing axis. The axes of third branching order had a significant and negative effect on the damping of the natural deformation mode. Results point out the major role played by foliage, qualitatively and quantitatively, on the damping of tree motions and on coupling the motions of the crown components.     

Rhamnaceae with multiple lateral buds: an architectural analysis

TOURN, G. M., TORTOSA, R. D. & MEDAN, D., 1992. Rhamnaceae with multiple lateral buds: an architectural analysis. A study was made of the morphology and architecture of three species of Rhamnaceae (Ziziphusjujuba, Zjziphus mistol and Paliurus spina-Christi) with multiple lateral buds. The developmental potential of individual meristems of bud complexes was studied and different kinds of shoots were recognized: vegetative long shoots (dominant and subordinate), flowering branches, short shoots and thorn-tipped branchlets. According to the different orders of branching and the patterns of growth, the architectural model for every species was determined. The architecture of the three species does not conform to that of known tree models. Ziziphus mistol and Paliurus spina-Christi have an architecture intermediate between Attim's and Roux's models; Ziziphusjujuba results in a combination of Koriba's and Roux's models.