| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
0 Department of Natural Resources Conservation, University of Massachusetts, Amherst, Massachusetts 01003 USA
Received for publication July 7, 1998. Accepted for publication July 9, 1999.
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONAPICAL CONTROL OF BRANCH...APICAL CONTROL OF BRANCH...DISCUSSIONLITERATURE CITED |
|---|
Key Words: allocation • apical control • branch angle • branch growth • growth stress
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONAPICAL CONTROL OF BRANCH...APICAL CONTROL OF BRANCH...DISCUSSIONLITERATURE CITED |
|---|
|
There are different types of lateral branches in woody plants. Sylleptic lateral branches develop from lateral meristems without a period of dormancy while the terminal shoot is elongating; proleptic lateral branches develop from lateral buds after a period of dormancy (Hallé, Oldeman, and Tomlinson, 1978
). Brown, McAlpine, and Kormanik (1967)
proposed the term "apical control" to describe the inhibition of growth of proleptic branches in contrast to the term "apical dominance" to describe bud formation though inhibition of growth of sylleptic branches. Thus, in temperate plants when a lateral meristem is formed apical dominance determines whether the meristem initially forms a sylleptic branch or forms a bud. In the second year apical control regulates the amount of elongation and diameter growth of proleptic branches from the previously dormant buds. Some buds do not form proleptic branches after the initial period of dormancy. These buds may enter the bud bank and subsequently form epicormic branches, a third type of branch (Wilson and Kelty, 1994
). Epicormic branches generally grow rapidly, are often near-vertical, and are the source of reiteration in tropical trees (Hallé, Oldeman, and Tomlinson, 1978
). Epicormic branches may function as replacement branches in species whose branches cannot bend up, such as the plagiotropic branches of Araucaria (House et al., 1998
). In this paper I will restrict the term apical control to the regulation of the primary and secondary growth of proleptic lateral branches, both young and old, that have grown from a bud following a single period of dormancy.
There are minor disagreements about terminology. Cline (1997)
defines apical dominance in herbaceous plants "as the control exerted by the shoot apex over the outgrowth of the lateral buds." He proposes that the term apical control applies to the control exerted on lateral shoots after the bud has started elongating, even though the bud has not passed through a period of dormancy. Europeans use the term "acrotony," somewhat comparable to apical control, to indicate the dominant growth of the uppermost, distal, laterals after bud dormancy in woody plants (Champagnat, 1978
). We should not let differences in terminology obscure the probability that as the phenomena of branch growth change during development from lateral meristem formation to a large, woody, lateral branch, the mechanisms controlling growth also change. Mechanisms of apical dominance in herbaceous plants should not just be assumed to apply to apical control phenomena in all stages of branch growth in woody plants.
An important characteristic of apical control, in contrast to apical dominance, is that dormant lateral buds on the same parent shoot that do grow out the first year all grow out at about the same time and produce leaves. The initial outgrowth of proleptic buds appears to be independent of apical control (Leakey and Longman, 1986
; Suzuki, 1990
). Subsequently apical control is asserted so the uppermost, distal lateral becomes the longest and the lowest, proximal lateral may scarcely elongate. Thimann (1977)
stated that the basic research question for apical dominance is why some lateral buds do not grow. The key problem for apical dominance is what triggers the start of growth. In contrast, all the buds that grow after dormancy is broken form leaves. The basic research question for apical control seems to be why some lateral shoots stop growing sooner than others. The key problem is what inhibits further growth of lower, proximal lateral shoots. I should stress that apical control inhibits not only shoot elongation, as in apical dominance, but also cambial activity and thickening of existing branches.
Leaf and internode number of new shoots are fixed in some species (Fig. 1). Leaf production and shoot elongation are limited to preformed leaves and internodes in the bud with, or without, apical control. Radial growth by cambial activity is not fixed in the bud so shoots with fixed growth can grow more in diameter after apical control is removed. Other species have free growth with the potential for production of additional neoformed leaves and internodes. Removing apical control of a free-growth branch allows the branch to produce neoformed leaves and increase elongation during the first year after release. Removing apical control in species with fixed growth has little effect on shoot elongation the first year, unless there is a second flush of growth (Little, 1970
; Wilson, 1992
). In fixed-growth species shoot length and leaf number increases are delayed until the second year (Fig. 1). The buds formed at the end of the first year after release from apical control are larger, with more leaves, than when under apical control. In fixed-growth species apical control of shoot length and leaf number is expressed during lateral bud formation, which determines leaf and internode number and thus shoot size for the next year.
|
APICAL CONTROL OF BRANCH GROWTH |
|---|
|
TOPABSTRACTINTRODUCTIONAPICAL CONTROL OF BRANCH...APICAL CONTROL OF BRANCH...DISCUSSIONLITERATURE CITED |
|---|
|
), or higher order, slower growing, branches (Remphrey and Davidson, 1992
), or in old slow-growing trees (Moorby and Wareing, 1963
). Therefore, any environmental effect that reduced overall growth rates could indirectly reduce apical control. Most research has been done on first-order lateral branches (using the botanical numbering system) arising from a vertical, central, parent shoot. I will call this first-order shoot the stem. A first-order branch off the stem may live for decades. The terminal of the stem, or of a branch, is the current annual elongation growth. Therefore, parent shoots and lateral branches of all orders all have terminals.
Hormones
The hormonal hypothesis for apical dominance was developed by Thimann and Skoog to explain apical dominance in herbaceous species (Thimann, 1977
). The original proposed mechanism was that auxin from the parent terminal directly inhibited lateral bud growth. Subsequently the mechanism was modified to include the action of other hormones, particularly cytokinins (Thimann, 1977
). Strong support for the effect of auxin comes both from auxin replacement experiments where auxin applied to a decapitated terminal shoot inhibits growth of lateral buds and from experiments using TIBA (tri-iodo benzoic acid) to block auxin transport and remove apical dominance (Cline, 1997
).
Auxin is transported polarly from shoot tip toward the roots. In Pinus sylvestris both the terminal shoot and branches contribute auxin to the stem, and the stem can also produce some of its own auxin (Sundberg and Uggla, 1998
). The polar nature of apical control parallels the polar transport of auxin. Generally the uppermost, distal shoots inhibit the lower, proximal shoots. Several experiments modify this polar pattern. Laterals of Populus deltoides seedlings were all the same length, rather than showing the "normal" decrease in length from tip to base, when the plants are grown under long days, warm temperatures, and high nutrients (Richards and Larson, 1981
). Changing the angle of rooted cuttings of Triplochiton scleroxylon eliminated, or even reversed, the pattern of lateral shoot lengths (Leakey and Longman, 1986
). It seems reasonable that treatments that affect patterns of shoot length also affect polar transport, but the hypothesis has not been tested.
There are relatively few experiments on hormonal action in apical control. Auxin in high concentrations applied to the decapitated or girdled stem of a woody plant can replace apical control and inhibit branch diameter growth, upward bending, and production of neoformed leaves in free growth species (Wilson and Archer, 1983
; Timell, 1986
, pp. 1189–1193; House et al., 1998
). Although TIBA apparently blocks auxin transport through woody shoots (Kennedy and Farrar, 1965
), I am not aware of experiments using TIBA or other auxin transport inhibitors to remove apical control over woody branches. Some experiments do not seem to support the auxin hypothesis for apical control. In Pinus strobus, a girdle just below a branch removes apical control even though the branch and the terminal shoot are still in direct connection and movement of hormones from terminal to lateral was, presumably, not affected (Münch, 1938
; Wilson, 1981
). Therefore, although auxin probably is involved in apical control, it is not clear how.
There is good evidence that hormones in addition to auxin regulate the amount of lateral shoot growth in plants. High cytokinin to auxin ratios were associated with fast growth of laterals in Lupinus, a nonwoody plant, (Emery, Longnecker, and Atkins, 1998
). In Picea abies, a fixed-growth tree, there was a positive correlation between cytokinin (zeatin riboside) content and lateral bud size during the critical period of bud formation that determines shoot length (Chen, Bollmark, and Eliasson, 1996
). Gibberellins can overcome apical control in a number of conifer species and ethylene also appears to be involved (Timell, 1986
, pp. 1197–1199).
Experimental applications of exogenous hormones clearly implicate hormones in both apical dominance and apical control. Measurements of endogenous hormone levels in relation to elongation and cambial activity in woody plants are often inconsistent with results from exogenous treatments (Little and Pharis, 1995
). The field of hormonal control seems to be in a phase of reassessment. The next step may be, as suggested by Cline (1994)
, the use of transgenic plants with different endogenous hormone levels. Unfortunately for advancement in knowledge of apical control, current work on transgenic plants is primarily on herbaceous plants (Schmitz and Theres, 1999
).
Transport of water and mineral nutrients
One hypothesis is that transport of water and nutrients to the lateral branch is restricted relative to transport to the terminal shoot and therefore branch growth is reduced relative to the terminal. Borchert and Honda (1984)
used this hypothesis to successfully simulate branching in a tree by assuming that growth was controlled by flux distribution among branches. Studies of hydraulic architecture support the hypothesis. In trees the hydraulic conductivity of branches is lower than the conductivity of the terminal, particularly at the junction between the terminal and the branch (Zimmermann, 1978
; Ewers and Zimmermann, 1984
). The result of this "bottleneck" of low conductivity is that under drought condition the water potential will be lower in the branch than the stem, so growth would stop first in the branches and the branches will die before the main stem (Zimmermann, 1978
). Reduced water transport to branches would also reduce the flow of dissolved nutrients into the branch and therefore reduce growth.
Several observations suggest that differences in transport are the result, not the cause, of apical control. When a young branch of Douglas-fir (Pseudotsuga menzeisii) is released from apical control it bends up and replaces the leader. As the replacement leader grows and produces new xylem its hydraulic conductivity gradually increases, but after 15 months it is still less than in a leader (Spicer and Gartner, 1998
). Thus, changes in hydraulic conductivity lag far behind the release from apical control. Phillips (1975)
pointed out that phloem girdling above a branch does not affect nutrient (or water) transport to the terminal, but does remove apical dominance. This observation also applies to Pinus strobus where phloem girdles above a branch eliminate apical control without affecting terminal growth and presumably water flow (Wilson and Archer, 1981
). Girdles below branches also eliminate apical control in Pinus strobus. If these girdles had any effect on xylem transport, the hydraulic conductance would be reduced below the branch–stem junction and should have no effect on the relative hydraulic conductance of the stem and branch above the girdle.
Photosynthesis
Older branches appear to be largely autonomous for assimilate and depend on their own photosynthesis for assimilate (Sprugel, Hinckley, and Schaap, 1991
). Therefore, increased rates of photosynthesis after release from apical control could increase branch growth. Leverenz (1981)
found that on large branches the first-order terminals have higher rates of photosynthesis and transpiration than the higher order laterals, even though there was no difference in water potential. He did not test the effect of decapitating the terminal on photosynthesis in the laterals. The terminal may depresses photosynthesis in the lateral. If this phenomenon occurs, when the terminal is removed the photosynthetic rate of the leaves on the lateral would increase. Compensatory increases in photosynthesis can occur after partial defoliation in conifers and angiosperms (Reich et al., 1993
; Pinkard et al., 1998
). Photosynthesis in remaining leaves can increase 25–75% after partial defoliation. Although compensatory photosynthesis in a lateral after removing apical control has apparently not been demonstrated, it would be consistent with increased growth after removing apical control.
Individual branches in the light grow larger than those in the shade (Stoll and Schmid, 1998
). These well-lit branches appear to escape some apical control, and they have a higher rate of photosynthesis. Part of the high rate of photosynthesis is due to the higher light intensity and part is due to increased branch growth and leaf area. Presumably the increased photosynthesis permits increased growth, and increased growth may, in turn, increase hormone production.
Moderate water or nutrient deficiencies under apical control would affect growth more than photosynthesis (Cannell and Dewar, 1994
). Therefore, factors that lead to decreased water or nutrients in branches compared to the terminal could stop branch growth without stopping branch photosynthesis and assimilate production. This assimilate would then be available for export to the terminal.
Assimilate allocation
Shoots under apical control all produce leaves, even the short shoots that scarcely elongate. Therefore, in contrast to apical dominance where leaves are not produced, all lateral shoots under apical control produce assimilate. The allocation hypothesis is that the parent shoot regulates the export of assimilate from the lateral branch. When the parent axis is intact, assimilate produced by the branch is exported, rather than being used for branch growth. When the parent shoot is removed, the lateral retains assimilate and continues to grow. Ford, Avery, and Ford (1992)
assumed for a simulation model that export from the branch began when branch growth requirements had been met. The allocation hypothesis suggests that retention of branch assimilate occurs when the branch sink strength exceeds the terminal sink strength.
Experiments with Pinus strobus support the importance of assimilate retention by branches. Pinus strobus has fixed growth. The initial response of the branch to release from apical control is prolonged cambial activity after the branch terminal shoot elongation stops (Wilson and Archer, 1981
). A stem girdle above a branch removes apical control. Indole-butyric acid (a synthetic auxin) applied to the proximal end of the girdle replaces apical control (Wilson, 1986
). A girdle 2 cm below a branch also removes apical control even though the branch is still in direct connection with the terminal (Münch, 1938
; Wilson, 1981
). A girdle 50 cm below the branch, however, does not remove apical control (Wilson, 1981, 1998
). My interpretation of these results is that the stem below the branch is a competitive sink for branch-produced assimilate. Auxin moving down the stem and branches by polar transport stimulates cambial activity and the competitive sink strength of the stem. A girdle above the branch stops auxin transport down the stem, reduces stem sink strength, permits the branch to retain assimilate, and removes apical control. Exogenous auxin added above the branch maintains cambial activity and sink strength in the stem below the branch and reimposes apical control. A girdle 2 cm below the branch makes the stem sink so small that it cannot compete with the branch and apical control is removed. A girdle 50 cm below the branch makes the stem sink big enough so that the normal levels of auxin moving down the stem create a competitive stem sink and apical control is maintained.
Girdling above a branch removes apical control in all species tested, but the interesting results from Pinus strobus are from girdles below branches. Therefore, I attempted to repeat the P. strobus experiments on other species. Girdling 2 cm below branches in the diffuse-porous angiosperms Acer rubrum and Betula lenta did not remove apical control in B. lenta and killed all stem and branch above the girdles in A. rubrum (Wilson, 1998
). It is not clear whether apical control is different in these angiosperms or whether the girdles interfere with xylem transport so shoots above the girdle die.
Several observations suggest that branches compete with each other, perhaps by competing for assimilates. Suzuki (1990)
thinned lateral buds on parent shoots, and the remaining buds produced longer shoots than in unthinned controls. Stoll and Schmid (1998)
observed that growth of Pinus sylvestris branches in the shade was greater when competing branches were also in the shade than when they were in the sun. They suggested that there was dynamic competition among the branches and that the branches in the sun actually inhibited the growth of those in the shade. This effect would be similar to the effect of apical control, and it could be due to competitive sinks for assimilate.
Gravimorphism
The effects of shoot angle on shoot growth are called gravimorphism (Wareing and Nasr, 1961
). The observations are that shoots grow fastest if they are vertical and grow more slowly as their angle to vertical increases. Therefore, branches at an angle to vertical would grow more slowly than their more vertical parent shoot just because of gravimorphism. In addition, shoot angle can modify the effect of apical control within and between lateral shoots. Wareing and Nasr (1961)
pruned and disbudded cherry, plum, and black currant rootstocks so that there were only two laterals. In controls the uppermost lateral grew the most and was more vertical. Bending laterals to horizontal reduced their elongation. If only the upper lateral was bent horizontal, the lower lateral elongated the most and grew vertically as a replacement shoot. Thus, a branch bent to horizontal loses its capacity to control the growth of more proximal branches. Leakey and Longman (1986)
found that changing the orientation of rooted cuttings from vertical to horizontal reversed the pattern of lateral shoot length from the distal lateral being the longest when vertical to the proximal being the longest when horizontal.
Gravimorphism presumably contributes to the reduced growth of lateral branches that are out of vertical, but why would gravimorphism effects decrease after release from apical control? The branch starts to grow faster before there is any change in angle. Therefore, changes in angle cannot account for initial increases in growth rate, but may be a factor later after the branch bends upward.
|
APICAL CONTROL OF BRANCH ANGLE |
|---|
|
TOPABSTRACTINTRODUCTIONAPICAL CONTROL OF BRANCH...APICAL CONTROL OF BRANCH...DISCUSSIONLITERATURE CITED |
|---|
). Although plagiotropic branches cannot bend to vertical, both plagiotropic and orthotropic branches of rain-forest angiosperms are more upright in the light than in the shade (King, 1998
), presumably from increased branch growth in the light. Apical control of conifer branches, measured by the relative elongation of branch and stem terminals, is reduced in the shade, yet branch angle to vertical does not appear to decrease (O'Connell and Kelty, 1994
), probably because radial growth does not increase. Although this section discusses the upward bending of pre-existing woody branches, the geotropic angles of elongating shoots also affect branch angle. The elongating tip of a branch is often more vertical than the older portion of the branch, resulting in an upwardly curved branch, even though there was no upward bending of any woody portions of the branch.
Mechanics
Branches are complex cantilever beams that follow the laws of mechanics (Niklas, 1992
). A lateral shoot at an angle to vertical is always acted on by the downward bending moment from self-mass. The branch cannot bend up unless it can generate enough upward bending moment from differential growth stresses in new wood to overcome the downward bending moment. The upward bending moment is a function both of the level of differential growth stress in each wood cell and of the amount of new wood with that differential growth stress. Therefore, from a mechanical point of view, apical control of branch angle can result from regulating the level of differential growth stress in new wood, the amount of new wood with stresses (radial growth), or both.
Some woody plants apparently cannot produce wood with differential growth stresses and therefore their branches cannot bend up. Their only response to release from apical control is increased radial growth (Wilson, 1998
). Most woody plants can generate differential growth stresses in wood, usually, but not necessarily, associated with formation of specialized wood (Wilson and Gartner, 1996
). Upward bending moment apparently can be generated by the bark in some tropical species (Fisher and Mueller, 1983
).
What is the relative importance of radial growth and the generation of growth stresses? Studies so far suggest that release from apical control always results in an increase in branch diameter growth, even in shrubs that cannot generate growth stresses and whose branches cannot bend up (Wilson, 1998
). Growth stresses in conifer wood are generated primarily by compression wood cells. Compression wood cells are produced in most (not all) branches under apical control (Timell, 1986
, p. 865), but not enough compression wood cells are produced to bend the branch up. After removing apical control of Pinus strobus branches, the level of growth stress was a function of the number of compression wood cells rather than different levels among the cells (Wilson, 1986
). Therefore, the major effect of removing apical control in conifers seems to be to increase radial growth, because compression wood is being formed anyway
Most angiosperms generate upward bending moments by producing tension wood, although bending moments can be generated from apparently normal wood (Wilson and Gartner, 1996
). In Prunus serotina and Fraxinus americana, branches under apical control formed no tension wood, but those with decapitated terminals formed tension wood and bent up (Wilson and Archer, 1983
). Therefore, in contrast to conifers, in angiosperms release from apical control may trigger the formation of tension wood along with increased radial growth.
Equilibrium position
The equilibrium position is the most mysterious aspect of branch angle. The equilibrium position is that position where the branch does not produce wood with differential growth stresses. If a branch is bent to either a more (upward), or less (downward), vertical position than the equilibrium position, it will tend to bend back toward the equilibrium position. Therefore, a branch will not bend itself to vertical if the equilibrium position is out of vertical. If the equilibrium position of a shoot is vertical the shoot is called orthotropic, and, if the equilibrium position is out of vertical, the shoot is called plagiotropic.
Some branches are irreversibly plagiotropic and will never bend up to vertical after removal of apical control. The classic example is Araucaria (Timell, 1986
). The equilibrium position of other plagiotropic branches apparently can change after release from apical control. Rooted cuttings of Pseudotsuga menziesii branches, for example, grow plagiotropically at angles to vertical for a year or more before they bend upward to vertical (Starbuck and Roberts, 1983
). Pinus strobus branches are initially plagiotropic after decapitation of the terminal, but eventually they bend upwards to vertical and become orthotropic (Wilson, 1973
). Apparently the equilibrium position of new differentiating wood cells eventually changes to vertical in the absence of apical control. Therefore, apical control seems to maintain the equilibrium position of these branches with reversible plagiotropy, but changes occur slowly after release from control.
Orthotropic branches may grow at an angle to vertical. If the initial branch angle is out of vertical, there will be a downward bending moment from self-mass. The branch will stay at an angle if it does not grow radially fast enough under apical control to bend upward to vertical. After removing apical control, the radial growth and upward bending moment of the branch increase and it can bend upward.
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONAPICAL CONTROL OF BRANCH...APICAL CONTROL OF BRANCH...DISCUSSIONLITERATURE CITED |
|---|
Compensatory photosynthesis after removing apical control is possible, although there are no data to test whether it occurs. Compensatory photosynthesis seems most likely when removing apical control significantly reduces leaf area. Girdling, which does not affect total leaf area, may not result in compensatory photosynthesis, particularly when the girdle is below a branch in Pinus strobus.
Hormone production and assimilate retention by the branch are the most likely candidates for the primary causes of apical control. The two factors are interrelated and are difficult to separate. Reduced hormone production under apical control, or changes in ratios of hormones produced, could stop branch growth and stop the branch sink for assimilate. Therefore, removing apical control would prolong hormone production by the branch at promotive levels and prolong the branch sink at competitive levels. The question would then become how the controlling parent shoot regulates hormone production by the branch. An alternative mechanism is that reduced assimilates, due to export to the stem, inhibit growth even with adequate hormones. In this case, removing apical control would reduce the strength of the competitive sink in the parent shoot or stem, permit assimilate retention in the branch, and allow continued growth of the branch and production of hormones by the branch.
Branch growth seems to be determined by the relative competitive abilities of the branch and the parent axis. A branch can partially escape apical control if it grows fast enough. Growth of lateral shoots can be increased with high light. The increase could be from more photosynthesis and more available assimilate, or it could be from changes in hormone production, or both. Unlike apical dominance, where laterals either grow or do not grow, there is a wide range of levels of apical control under different conditions both between and within individual plants.
Increased branch diameter growth and production of upward bending moments after release from apical control are both important factors in the upward bending of a branch. Increased diameter growth is associated with assimilate retention. The regulation of the formation of growth stresses that cause upward bending moments, for example by reaction wood formation, appears to be a different phenomenon. Timell (1986)
thoroughly reviewed aspects of apical control primarily, but not exclusively, of compression wood formation by conifers. He concluded (p. 1246) that "the total evidence is too contradictory and sometimes downright confusing" to reach definite conclusions. The situation has not changed significantly. The question of how, or even whether, apical control regulates the equilibrium position of a branch, and thus regulates the formation of reaction wood and growth stresses, remains open.
Apical control is so widespread and covers so many aspects of growth that there probably is no single mechanism for all the phenomena involved. It is possible that different mechanisms act on the central process of assimilate allocation. We should be prepared to deal with a complex system. The mechanisms are probably different for the growth processes determining bud size, shoot elongation, and cambial activity. Mechanisms controlling elongation and diameter growth are almost certainly different from those controlling growth stress development in wood cells. In addition, there may be differences among various woody species. It is desirable to test hypotheses and repeat experiments in conifers and angiosperms, both fixed- and free-growth species. Before trying to experiment with basic mechanisms at the cell level we need better descriptions of the phenomena involved in apical control.
|
FOOTNOTES |
|---|
|
LITERATURE CITED |
|---|
|
TOPABSTRACTINTRODUCTIONAPICAL CONTROL OF BRANCH...APICAL CONTROL OF BRANCH...DISCUSSIONLITERATURE CITED |
|---|
Brown, C. M., R. G. McAlpine, and P. P. Kormanik. 1967 Apical dominance and form in woody plants: a reappraisal. American Journal of Botany 54: 153–162.[CrossRef][ISI]
Cannell, M. G. R., and C. Dewar. 1994 Carbon allocation in trees: a review of concepts for modeling. Advances in Ecological Research 25: 59–104.
Champagnat, P. 1978 Formation of the trunk in woody plants. In P. B. Tomlinson and M. H. Zimmermann [eds.], Tropical trees as living systems, 401–422. Cambridge University Press, Cambridge, UK.
Chen, H.-J., M. Bollmark, and L. Eliasson. 1996 Evidence that cytokinin controls bud size and branch form in Norway spruce. Physiologia Plantarum 98: 612–618.[CrossRef]
Cline, M. G. 1994 The role of hormones in apical dominance: new approaches to an old problem in plant development. Physiologia Plantarum 90: 230–237[CrossRef]
———. 1997 Concepts and terminology of apical dominance. American Journal of Botany 84: 1064–1069.[Abstract]
Emery, R. J. N., N. E. Longnecker, and C. A. Atkins. 1998 Branch development in Lupinus angustfolius L. II relationship with endogenous ABA, IAA and cytokinins in axillary and main stem buds. Journal of Experimental Botany 49: 555–562.
Ewers, F. W., and M. H. Zimmermann. 1984 The hydraulic architecture of balsam fir (Abies balsamea). Physiologia Plantarum 60:453–458.
Fisher, J. B., and R. J. Mueller. 1983 Reaction anatomy and reorientation in leaning stems of balsa (Ochroma) and papaya (Carica). Canadian Journal of Botany 61: 880–887.
Ford, E. D., A. Avery, and R. Ford. 1992 Simulation of branch growth in the Pinaceae: interactions of morphology, phenology, foliage productivity, and the requirements for structural support, on the export of carbon. Journal of Theoretical Biology 146: 15–36.
Forrester, J. W. 1968 Principles of systems. Wright-Allen Press, Cambridge, Massachusetts, USA.
Hallé, F., R. A. A. Oldeman, and P. B. Tomlinson. 1978 Tropical trees and forests: an architectural analysis. Springer-Verlag, New York, New York, USA.
House, S., M. Dieters, M. Johnson, and R. Haines. 1998 Inhibition of orthotropic replacement shoots with auxin treatment on decapitated hoop pine, Araucaria cunninghami, for seed orchard management. New Forests 16: 221–230.[CrossRef][ISI]
Kennedy, R. W., and J. L. Farrar. 1965 Induction of tension wood with the anti-auxin 2,3,5 tri-iodobenzoic acid. Nature 208: 406–407.
King, D. A. 1998 The relationship between crown architecture and branch orientation in rain forest trees. Annals of Botany 82: 1–7.
Leakey, R. R. G., and K. A. Longman. 1986 Physiological, environmental and genetic variation in apical dominance as determined by decapitation in Triplochiton scleroxylon. Tree Physiology 1:193–207.
Leverenz, J. W. 1981 Photosynthesis and transpiration in large forest-grown Douglas-fir: interactions with apical control. Canadian Journal of Botany 59:2568–2576.
Little, C. H. A. 1970 Apical dominance in long shoots of white pine (Pinus strobus). Canadian Journal of Botany 48: 239–253.
———, and R. P. Pharis. 1995 Hormonal control of radial and longitudinal growth in the tree stem. In B. L. Gartner [ed.], Plant stems: physiology and functional morphology, 281–219. Academic Press, New York, New York, USA.
Moorby, J., and P. F. Wareing. 1963 Aging in woody plants. Annals of Botany 27: 291–308.
Münch, E. 1938 Investigations on the harmony of tree shape. Jahrbücher für wissenschaftliche Botanik 86: 581–673. (Translated by M. H. Zimmermann, 1963).
Niklas, K. J. 1992 Plant biomechanics. University of Chicago Press, Chicago, Illinois, USA.
O'Connell, B. M., and M. J. Kelty. 1994 Crown architecture of understory and open-grown white pine (Pinus strobus L.) saplings. Tree Physiology 14: 89–102.
Phillips, I. D. J. 1975 Apical dominance. Annual Review of Plant Physiology 26: 341–367.[ISI]
Pinkard, E. L., C. L. Beadle, N. J. Davidson, and M. Battaglia. 1998 Photosynthesis response of Eucalyptus nitens (Deane and Marden) Maiden to green pruning. Trees 12: 119–128.
Reich, P. B., M. B. Walters, S. C. Krause, D. W. Vanderklein, K. F. Raffa, and K. F. Tabone. 1993 Growth, nutrition and gas exchange of Pinus resinosa following artificial defoliation. Trees 7: 67–77.
Remphrey, W. R., and C. G. Davidson. 1992 Branch architecture and its relation to shoot tip abortion in mature Fraxinus pennsylvanicum. Canadian Journal of Botany 70: 1147–1153.
Richards, J. H., and P. R. Larson. 1981 Morphology and development of Populus detoides branches in different environments. Botanical Gazette 142: 382–393.[CrossRef]
Schmitz, G., and K. Theres. 1999 Genetic control of branching in Arabidopsis and tomato. Current Opinion in Plant Biology 2: 51–55.[CrossRef][ISI][Medline]
Spicer, R., and B. L. Gartner. 1998 How does a gymnosperm branch (Pseudotsuga menseisii) assume the hydraulic status of a main stem when it takes over as a leader? Plant, Cell and Environment 21: 1063–1070.[CrossRef]
Sprugel, D. G., T. M. Hinckley, and W. Schaap. 1991 The theory and practice of branch autonomy. Annual Review of Ecology and Systematics 22: 309–322.[CrossRef][ISI]
Starbuck, C. J., and A. N. Roberts. 1983 Compression wood in rooted cuttings of Douglas-fir. Physiologia Plantarum 57: 371–374.[CrossRef]
Stoll, P., and B. Schmid. 1998 Plant foraging and dynamic competition between branches of Pinus sylvestris in contrasting light environments. Journal of Ecology 86: 934–945.[CrossRef]
Sundberg, B., and C. Uggla. 1998 Origin and dynamics of indoleacetic acid under polar transport in Pinus sylvestris. Physiologia Plantarum 104: 22–29.
Suzuki, T. 1990 Apical control of lateral bud development and shoot growth in mulberry (Morus alba): effects of position of lateral and accessory buds and leaves. Physiologia Plantarum 80: 350–356.[CrossRef]
Thimann, K. V. 1977 Hormone action in the whole life of plants. University of Massachusetts Press, Amherst, Massachusetts, USA.
Timell, T. E. 1986 Compression wood in gymnosperms. Springer-Verlag, New York, New York, USA.
Wareing, P. F., and T. A. A. Nasr. 1961 Gravimorphism in trees I. Effects of gravity on growth and apical dominance in fruit trees. Annals of Botany 25: 321–340.
Wilson, B. F. 1973 White pine shoots: roles of gravity and epinasty in movements and compression wood location. American Journal of Botany 60:597–601.
———. 1981 Apical control of diameter growth in white pine branches. Forest Science 27: 95–101.[ISI]
———. 1986 Apical control of compression wood action in white pine branches. Wood Science and Technology 20: 111–117.
———. 1992 Compensatory growth in shoot populations of young white pine trees. Trees 6: 204–209.
———. 1998 Branches versus stems in woody plants: control of branch diameter growth and angle. Canadian Journal of Botany 76: 1852–1856.[CrossRef]
———, and R. R. Archer. 1981 Apical control of branch movements in white pine: biological aspects. Plant Physiology 68:1285–1288.
———, and ———. 1983 Apical control of branch movements and tension wood in black cherry and white ash trees. Canadian Journal of Forest Research 13: 594–600.
———, and B. L. Gartner. 1996 Lean in red alder (Alnus rubra): growth stress, tension wood and righting response. Canadian Journal of Forest Research 26: 1951–1956.[CrossRef]
———, and M. J. Kelty. 1994 Shoot growth from the bud bank in black oak. Canadian Journal of Forest Research 24: 149–154.
Zimmermann, M. H. 1978 Hydraulic architecture of some diffuse-porous species. Canadian Journal of Botany 56: 2286–2295.
This article has been cited by other articles:
|
|
 |
|
  P.-E. Lauri Differentiation and growth traits associated with acrotony in the apple tree (Malus xdomestica, Rosaceae) Am. J. Botany, August 1, 2007; 94(8): 1273 - 1281. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Renton, Y. Guedon, C. Godin, and E. Costes Similarities and gradients in growth unit branching patterns during ontogeny in 'Fuji' apple trees: a stochastic approach J. Exp. Bot., September 1, 2006; 57(12): 3131 - 3143. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. LEBON, A. PELLEGRINO, G. LOUARN, and J. LECOEUR Branch Development Controls Leaf Area Dynamics in Grapevine (Vitis vinifera) Growing in Drying Soil Ann. Bot., July 1, 2006; 98(1): 175 - 185. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. G. PUNTIERI, M. S. SOUZA, C. BRION, C. MAZZINI, and D. BARTHELEMY Axis Differentiation in Two South American Nothofagus Species (Nothofagaceae) Ann. Bot., October 1, 2003; 92(4): 589 - 599. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. G. Cline and K. Sadeski Is auxin the repressor signal of branch growth in apical control? Am. J. Botany, November 1, 2002; 89(11): 1764 - 1771. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. COSTES and Y. GUEDON Modelling Branching Patterns on 1-year-old Trunks of Six Apple Cultivars Ann. Bot., May 1, 2002; 89(5): 513 - 524. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
