共查询到20条相似文献,搜索用时 31 毫秒
1.
Hilary Woodcock Pierre Vollenweider Rolf Dubs Rose-Marie Hofer 《Trees - Structure and Function》1995,9(5):279-288
One of the first symptoms expressed by declining trees is reduced growth in stem diameter and length increment. The possibility of a relationship between length increment and crown thinning in beech (Fagus sylvatica L.) was investigated by developing a computer model to simulate first order branching patterns of the apical 2 m of monopodially branching beech trees, 70–100 years old, for a range of length increment rates. The model was based on values for branching angle, main axis and branch length increment, number of branches produced per year and branch mortality rates for six healthy and declining trees. Shoot growth rates in the apical 2 m of the sample trees ranged from about 5 cm/year (decline class 3) to 43 cm/ year (healthy). Simulations of branching patterns in the apical 2 m of trees growing at different rates indicated that, when growth rate exceeded about 20 cm/year, total first order branch length and area explored were independent of growth rate. When growth rates fell below this value there was a reduction in total area explored and first order branch length due primarily to the formation of fewer branches. More acute branching angles contributed to a reduction in the area explored. Growth rate-related crown thinning could increase the risk of bark necrosis and secondary pathogen infection during dry and/or hot spells. 相似文献
2.
Summary The two dominant species of the Corsican mattoral,Arbutus unedo L. andErica arborea L., can produce abundant sprouts from the lignotuber not only immediately after fire but also more or less continuously in the absence of major disturbance. The lignotuber appears to be more important during the early stages of development; the result is an increase in the number of sprouts during the 25 years following the establishment of the individuals. Later the lignotuber seems to lose the ability to ensure the development of new basal sprouts. A hypothesis is that the presence of a lignotuber is related to the growth form.Arbutus unedo andErica arborea show behaviour intermediate between acrotony and basitony, as the shoots show acrotony, and continuous sprouting is characteristic of basitonic species. The fact that sprouting from the lignotuber is not necessarily a result of fire suggests that the relation between fire and vegetation in the Mediterranean region should be reconsidered. 相似文献
3.
Architectural analysis and modelling of the branching process of the young oil-palm root system 总被引:1,自引:1,他引:0
An architectural analysis of the root system of young oil-palm (Elaeis guineensis Jacq.) seedlings was made. In this analysis, root branching was modelled by a Markov chain (discrete-time, discrete-state space stochastic process). This study has been realized on radicles of young oil-palm seedlings which were considered as main axes which branch. We defined an elementary length unit as the smallest length between two successive lateral roots. The model was based on the analysis of a sequence of events, each event being indexed by the rank of the elementary length unit on the main axis. An event was defined as the state of the length unit, chosen between unbranched state and three branched-state categories. The branching process of the oil-palm radicle was modelled by a four-state first-order Markov chain. Consequently, the state of an elementary length unit depended only on the state of the previous one. The Markov chain was homogeneous, i.e. the transition probabilities did not depend on the rank of the elementary length unit.This study allowed us to identify a probabilistic model of root branching which was the first step in the elaboration of a stochastic model of the architecture of the oil-palm root system. 相似文献
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5.
为了探讨干热河谷盆地辣木种植密度与分枝格局和生物量的关系及较为合理的种植密度,通过野外实地调查和数据分析对该地区不同栽培密度辣木人工林分枝格局及生物量进行研究,结果表明:辣木林分在株高、地径、冠幅以及分枝数量方面与栽培密度呈现显著负相关;不同密度下,根、茎、叶生物量及果荚数和果荚均长、直径和果荚均仔粒数之间都存在显著的差异性;栽培密度对辣木的分枝格局有较显著影响,主要表现在一级/二级分枝率、二级/三级分枝率以及三级分枝长度上有显著差异;辣木在不同方位上分枝格局有明显差异,主要体现在主、侧枝分枝长度和一级分枝角度上的差异显著;在本试验范围内,以叶用辣木为培育目标的较适宜的栽培密度为株行距0.9m×0.9m,以果用为栽培目标的较适宜的栽培密度为株行距1.5m×1.5m。在不同的栽培密度下,辣木人工林之间分枝格局及生物量的显著性差异,反映了辣木随环境的变化具有较高的形态可塑性和生态适应性。 相似文献
6.
Yukihiro Chiba 《Ecological Research》1991,6(1):21-28
Ramification in tree structure was investigated by the main axis cutting method, which differs from the ordinary stratified
clipping method. An axis running from the arbitrary terminal leader of the shoot to the stem base was termed the “main axis”.
Cutting the main axis into pieces of constant length gives the “segment layer”, which consists of segments of the main axis
and all branches and leaves diverging from the respective segments. There was a linear relationship between the weight of
a main axis segment (in the range where leaves exist) of constant length and that of all the parts above the segment. Since
plant form is determined by branches diverging regularly from the mother branch or stem, this linear relationship is considered
to support the concept of the pipe model theory. It is also suggested that the proportionality constant of the linear relationship
may specify the branching structure or ramifications of plant form. 相似文献
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Reinvestigation of Nystroemia pectiniformis Halle from the Upper Shihhotze Formation of Shanxi Province, China, has led to the identification of new and important features of this enigmatic Late Permian seed plant, permitting its typification and diagnosis. After reassembling several of the previously studied specimens to form a single articulated branching system comprising at least four orders of branching, previously unknown features of its branching pattern and morphology have been characterized. First–order axes are wide and branch to one side only, bearing second–order branches either singly or in pairs and of two kinds: one fertile and bearing characteristic ovulate branching systems and the other presumably vegetative. Ovulate second–order axes are narrow and branch to one side only, producing numerous, closely spaced lateral branches in two alternate to sub–opposite rows. Lateral branches are slender and produce numerous ovulate branching systems to one side of the axis only. Ovulate branching systems divide unequally to produce 3–15 ultimate axes of different lengths that are planated. Each ultimate axis bears a single terminal ovule with 180 degree rotational symmetry and two horn–like integumentary projections distally. The other kind of second–order axes are distinct from those bearing ovules; they are wider and longer and branches occur on both sides of the secondary axis, lacking divisions in close proximity to the first–order axis. These have only been observed incomplete although their distinct morphology indicates they are unlikely to be ovulate branches from which ovules/seeds have been shed. Additional organs of the Nystroemia plant are considered, including pollen organs previously assigned by Halle to the same species (displaying its characteristic branching style), and also leaves of Chiropteris reniformis Halle that were probably borne on the larger kind of second–order branches. Implications of Nystroemia on seed plant evolution and distribution are discussed, and it is concluded that this most likely represents a late stratigraphic occurrence of a plesiomorphic hydrasperman–type seed plant with affinities closely allied to members of the Lyginopteridales. 相似文献
9.
DE-MING WANG SHOU-GANG HAO QI WANG 《Botanical journal of the Linnean Society. Linnean Society of London》2003,142(3):255-271
A new vascular plant, Hsüa deflexa sp. nov., is documented from the Lower Devonian ((upper) Pragian-lower Emsian) Xujiachong Formation, near Xujiachong village, Qujing District, eastern Yunnan, South China. In three dimensions, the branching system comprises a robust creeping main axis and comparatively slender erect lateral axes inserted oppositely or alternately. The lateral axes depart at right angles from the main axis. Towards the apex, the main axis is perhaps erect with the lateral axes attached at smaller angles. The lateral axes dichotomize equally one to three times in different planes and decrease in diameter and length acropetally. They bear sparse and irregular tiny spines. Apices of a pair of distal lateral axes curve in opposite directions and each terminates in a rounded to reniform sporangium. The sporangium dehisces into two equal valves along an indistinct convex marginal thickening. The xylem is possibly centrarch. This plant fits Hsüa in branching pattern, sporangial characters and xylem maturation. Hsüa deflexa sp. nov. differs mainly from the type species H. robusta in the presence of axial spines, perpendicular extension of lateral axes from the main axis and curving of distal lateral axes. Based on the possibly centrarch xylem and terminal sporangium, this plant relates to the rhyniophytes ( sensu Banks, 1968). In view of the equal sporangial valves with marginal thickenings it resembles the zosterophyllophytes ( sensu Banks, 1968). Hsüa is now treated as incertae sedis . © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 142 , 255−271. 相似文献
10.
Lisa Patrick Bentley James C. Stegen Van M. Savage Duncan D. Smith Erica I. von Allmen John S. Sperry Peter B. Reich Brian J. Enquist 《Ecology letters》2013,16(8):1069-1078
Several theories predict whole‐tree function on the basis of allometric scaling relationships assumed to emerge from traits of branching networks. To test this key assumption, and more generally, to explore patterns of external architecture within and across trees, we measure branch traits (radii/lengths) and calculate scaling exponents from five functionally divergent species. Consistent with leading theories, including metabolic scaling theory, branching is area preserving and statistically self‐similar within trees. However, differences among scaling exponents calculated at node‐ and whole‐tree levels challenge the assumption of an optimised, symmetrically branching tree. Furthermore, scaling exponents estimated for branch length change across branching orders, and exponents for scaling metabolic rate with plant size (or number of terminal tips) significantly differ from theoretical predictions. These findings, along with variability in the scaling of branch radii being less than for branch lengths, suggest extending current scaling theories to include asymmetrical branching and differential selective pressures in plant architectures. 相似文献
11.
The pipe model relationship (constancy of branch cross-sectional area/leaf area) and Leonardo da Vinci’s rule (equality of
total cross-sectional area of the daughter branches and cross-sectional area of their mother branch) are empirical rules of
tree branching. Effects of branch manipulation on the pipe model relationships were examined using five Acer rufinerve trees. Half the branches in each tree were untreated (control branches, CBs), and, for the others (manipulated branches,
MBs), either light intensity or leaf area (both relating to photosynthetic source activity), or shoot elongation (source + sink
activities), was reduced, and responses of the pipe model relationships were followed for 2 years. The pipe model relationship
in MBs changed by suppression of source activity, but not by simultaneous suppression of source + sink activities. The manipulations
also affected CBs in the year of manipulation and both branches in the next year. The branch diameter growth was most affected
by light, followed by shoot elongation and leaf area, in that order. Because of the decussate phyllotaxis of A. rufinerve, one branching node can potentially have one main and two lateral branches. Analysis of 295 branching nodes from 13 untreated
trees revealed that the da Vinci’s rule held in branching nodes having one shed branch but not in the nodes without branch
shedding, indicating the necessity of natural shedding of branches for da Vinci’s rule to hold. These analyses highlight the
importance of the source–sink balance and branch shedding in maintenance of these empirical rules.
This article was contributed at the invitation of the Editorial Committee. 相似文献
12.
We studied the development and structure of the unusual trichotomous branching of Edgeworthia chrysantha. Three "branch primordia" are formed sequentially on the shoot apex of a main axis and develop into trichotomous branching. The branch primordia are clearly distinguishable from the typical axillary buds of other angiosperms; they develop much more rapidly than axillary buds, and the borders between the branch primordia and shoot apex of the main axis are anatomically unclear. Furthermore, at a later stage, leaves subtending the branch primordia produce typical axillary buds. These results suggest that the trichotomous branching in this species involves the division of the shoot apical meristem. Expression analysis of genes involved in branching or maintenance of the shoot apical meristem in this species should clarify the control mechanism of this novel branching pattern in angiosperms. We also observed the phyllotactic patterns in trichotomous branching and have related these patterns to the shoot system as a whole. 相似文献
13.
Yasuji Fukuda 《Journal of plant research》1974,87(1):51-60
Phyllotaxis and branching system inTribulus terrestris were studied. Besides three nodal types already known in the species, a new type was found. The four nodal types were designated
as A (with one leaf and no flower), B (with one leaf and one flower), C (newly found type, with two leaves of different sizes
and no flower) and D (with two leaves of different sizes and one flower). A-type nodes are found only in basal parts of shoots,
while distal parts have exclusively D-type nodes. Between the nodes of the two types there is always one node of B-type. Occurrence
of C-type is rare and restricted to the first node of the lateral branch. The first leaf of the lateral branch superposes
to the leaves of the mother axis at maturity, but it is situated at first more or less laterally. On the basis of anatomy,
as well as gross morphology, the branching system at B- and D-type nodes was interpreted as sympodial, the main axis ending
in a flower. With regard to the manner of overlapping of sepal margins, right- and left-handed calyces were recognized. The
handedness always corresponds to the direction to which the peduncle is inclined. 相似文献
14.
在不同修剪手法下,对栽培桃树(Prunuspersica(L.)Batsch)不同母枝上的分枝模式进行了比较研究.从分枝模式来看:修剪后的母枝基本由3个不同的区域组成,基部是不萌发的潜伏芽形成的未分枝区域;中部是延迟分枝和多次分枝组成的分枝区域(主要的枝条类型有短枝、长枝和多次枝);顶部是被剪除的部分.我们通过隐式半马尔可夫模型来模拟这一分枝模式,主要是定量描述1次枝和多次枝在母枝上的数量及其分布状况.在上述模型中,未分枝区、延迟分枝区和多次分枝区称为瞬时态,被剪除的部分称为吸收态.模拟的结果与观察的结果进行对比后发现,两者具有很好的一致性.这说明隐式半马尔可夫模型是模拟植物分枝过程的一种有效方法,尽管隐式半马尔可夫链模型只是一个描述性的模型,但仍能对其所描述的生物现象进行解释,在预测修剪手法对母枝分枝模式影响方面比传统的方法具有明显的优势.本研究结果是建立三维虚拟桃树树冠分枝结构的基础. 相似文献
15.
16.
在不同修剪手法下,对栽培桃树(Prunuspersica(L.)Batsch)不同母枝上的分枝模式进行了比较研究。从分枝模式来看修剪后的母枝基本由3个不同的区域组成,基部是不萌发的潜伏芽形成的未分枝区域;中部是延迟分枝和多次分枝组成的分枝区域(主要的枝条类型有短枝、长枝和多次枝);顶部是被剪除的部分。我们通过隐式半马尔可夫模型来模拟这一分枝模式,主要是定量描述1次枝和多次枝在母枝上的数量及其分布状况。在上述模型中,未分枝区、延迟分枝区和多次分枝区称为瞬时态,被剪除的部分称为吸收态。模拟的结果与观察的结果进行对比后发现,两者具有很好的一致性。这说明隐式半马尔可夫模型是模拟植物分枝过程的一种有效方法,尽管隐式半马尔可夫链模型只是一个描述性的模型,但仍能对其所描述的生物现象进行解释,在预测修剪手法对母枝分枝模式影响方面比传统的方法具有明显的优势。本研究结果是建立三维虚拟桃树树冠分枝结构的基础。 相似文献
17.
Matthew D. Robbins Michael D. Casler Jack E. Staub 《Molecular breeding : new strategies in plant improvement》2008,22(1):131-139
Multiple lateral branching (MLB) is a quantitatively inherited trait associated with yield in cucumber (Cucumis sativus L.; 2n = 2x = 14). Although quantitative trait loci (QTL) have been identified for MLB and QTL-marker associations have been verified
by marker-assisted selection, the individual effects of these QTL have not been characterized. To test the effects of pyramiding
QTL for MLB, molecular genotyping was utilized to create two sets (standard- and little-leaf types) of inbred backcross (IBC)
lines possessing various numbers of QTL that promote branching. These IBC lines were evaluated for lateral branch number in
two Wisconsin environments at three plant densities. Highly significant differences in the number of primary lateral branches
were detected between spacings, leaf types, and lines, but not between locations. Lateral branch number decreased at higher
plant densities in all genotypes, while genotype by environment and QTL by environment interactions were marginally non-significant.
As the number of QTL increased among IBC lines, the number of branches did not generally change in the little-leaf lines,
but decreased in the standard-leaf lines, demonstrating an epistatic effect related to genetic background during lateral branch
development. The genomic location with the greatest effect on MLB was confirmed as the QTL that was previously mapped near
the little-leaf locus (ll), while the addition of one specific QTL consistently decreased the number of lateral branches in standard-leaf lines. Although
pyramiding QTL for MLB did not uniformly increase the number of lateral branches, pyramiding QTL in IBC lines allowed further
characterization of individual QTL involved in MLB. Our results, coupled with those of previous studies indicate that lateral
branch development in cucumber is determined by growing environment (i.e., plant spacing), genetic background, and QTL composition. 相似文献
18.
In the tropical tree Tabebuia rosea, seedlings form an erect unbranched stem with rhythmic growth. Three distinct and predictable geometrical stages are then recognized in crown development. Sympodial branching begins with the arrest of the terminal bud of the trunk and symmetric outgrowth of a pair of subtending lateral buds. During an intermediate phase, branching becomes asymmetric at about Order 5. At each sympodial bifurcation there is differentiation between vigorous, relatively straight main branches (leaders) and less vigorous laterals forming regular pseudomonopodial branch complexes, which collectively constitute the cup-shaped crown. Finally, dormant lateral buds in the lowest bifurcation of the trunk are released and reiterate the original crown form. Ultimately an erect, apparently monopodial tree is formed by a set of superimposed cup-shaped crowns. Crown development of Tabebuia is unique because it involves predictable ontogenic changes in branching patterns. Crowns of open-grown Tabebuia consist of relatively few, wide branch tiers, crowns of forest grown trees are tall and narrow. Analysis of the adaptive geometry of wide vs. narrow crowns through computer simulation illustrates the precise cost of mechanical support for terminal leaf rosettes at successive developmental phases and suggests that tall, erect, narrow, and multi-tiered crowns are more efficient than wide open crowns. 相似文献
19.
Branch development in Lupinus angustifolius L.#II. Relationship with endogenous ABA, IAA and cytokinins in axillary and main stem buds 总被引:3,自引:0,他引:3
The concentrations of indole-3-acetic acid (IAA), cytokinins (CK) and
abscisic acid (ABA) were measured in buds of different regions (main stem
and lateral branches) of Lupinus angustifolius L. (cv.
Merrit) and at different stages in the development of branches. In lupin,
branching patterns are the result of discrete regions of axillary branches
(upper, middle and basal) which elongate at much different rates. Early in
development only the main shoot elongates, followed usually by basal branch
growth and then rapid upper branch growth. Branches in the middle of the
main stem grow only weakly or fail to develop. Levels of IAA were generally
high in the apical buds of slowly growing branches and low in buds from
strongly growing branches, whereas CK levels showed the opposite
relationship. CK:IAA ratio showed a closer relationship with the rate of
growth of a particular branch better than the levels of either CK or IAA
alone. During early stages of growth ABA concentration did not follow the
rate of branch growth. However, later in development, where growth did not
closely match the ratio of CK:IAA, ABA level showed a strong negative
relationship with growth. A significant decrease in ABA was associated with
continued strong growth of the main stem apex following a decline in CK:IAA
ratio. Overall, the best relationship between the level of growth factors
in apical buds and branching pattern in lupin was the ratio of CK:IAA,
implying that high CK:IAA at a given bud would promote growth. ABA level
appeared to play a secondary role, as a growth
inhibitor. 相似文献
20.
Shade-induced changes in the branching pattern of a stoloniferous herb: functional response or allometric effect? 总被引:10,自引:1,他引:9
Shade-induced changes in the branching pattern of clonal plants can lead to conspicuous modifications of their growth form
and architecture. It has been hypothesized that reduced branching in shade may be an adaptive trait, enabling clonal plants
to escape from unfavourable patches in a heterogeneous environment by allocating resources preferentially to the growth of
the main axis (i.e. linear expansion), rather than to local proliferation by branching. However, such an adaptionist interpretation
may be unjustified if (1) branching frequency is a function of the ontogenetic stage of plants, and if (2) shading slows down
the ontogenetic development of plants, thereby delaying branch formation. In this case, architectural differences between
sun- and shade-grown individuals, harvested at the same chronological age, may not represent a functional response to changes
in light conditions, but may be a by-product of effects of shade on the rate of plant development. To distinguish between
these two alternatives, individuals of the stoloniferous herb Potentilla reptans were subjected to three experimental light conditions: a control treatment providing full daylight, and two shade treatments:
neutral shade (13% of ambient PPFD; no changes in light spectral composition) and simulated canopy shade (13% PPFD and a reduced
red:far-red ratio). Plant development was followed throughout the experiment by daily monitoring primary stolon growth as
well as branch and leaf initiation. Biomass and clonal offspring production were measured when plants were harvested. At the
end of the experiment shaded plants had produced significantly fewer branches than clones grown in full daylight. In all three
treatments, however, initiation of secondary stolons occurred at the same developmental stage of individual ramets. Shading
significantly slowed down the ontogenetic development of plants and this resulted in the observed differences in branching
patterns between sun- and shade-grown individuals, when compared at the same chronological age. These results hence provide
evidence that shade-induced changes in the branching pattern of clonal plants can be due to purely allometric effects. Implications
for interpreting architectural changes in terms of functional shade-avoidance responses are discussed.
Received: 16 August 1996 / Accepted: December 1996 相似文献