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A -C. Patterns of branch formation in cut trunks of M. azedarach. A, A cut trunk with smooth bark. Five branches were formed from suppressed buds that were formed above leaf bases before the leaves were shed. B, A rough and furrowed-barked main branch, showing a
Source publication
The bark texture of Melia azedarach L. changes from smooth to furrowed as trees age. In trees that were cut down, those with smooth bark sprouted below the cut from suppressed buds; trees with thick, furrowed bark sprouted at the edge of the cut surface from adventitious buds. The trees that had thin, furrowed bark sprouted mainly at the edge of th...
Contexts in source publication
Context 1
... difference in the pattern of bud development was observed between trunks in relation to bark type (Table 1). Stumps with smooth bark sprouted mainly from suppressed buds located above leaf scars ( Fig. 1 A). Only infrequently did they produce adventitious branches from callus at the cut cambial region surface. ...
Context 2
... mainly from suppressed buds located above leaf scars ( Fig. 1 A). Only infrequently did they produce adventitious branches from callus at the cut cambial region surface. Thick-diameter trunks with furrowed bark usually produced branches only from adventitious buds. The adventitious branches appeared in a whorl on the cut surface of the stump (Fig. 1 B). Infrequently, branches developed below the cut, from cracks in the furrowed bark ( Fig. 1 C), but this happened only in relatively thin (up to 250-ram-diameter) furrow-barked ...
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La investigación fue desarrollada en la Estación Forestal Plaza, un campo Anexo de la Estación Experimental Agropecuaria INTA Sáenz Peña, Chaco, Argentina. En una Parcela de pino plantada en el año 1963, raleada en el año 1990 y que sufrió un incendio en el año 1995, se establecio una densa regeneración natural dominada por paraísos diseminados des...
Citations
... Cork as a rule is not formed in fast growing shoots and it has been proposed that the lack of cork in such organs allows for better photosynthesis [23]. The above is suggests that auxin suppresses cork formation, a possibility further supported by the fact that cork initiation is delayed around buds and below leaves [24]. These holes and cracks in the cork were found to allow for quicker canopy regeneration in cases of canopy breakage [24]. ...
... The above is suggests that auxin suppresses cork formation, a possibility further supported by the fact that cork initiation is delayed around buds and below leaves [24]. These holes and cracks in the cork were found to allow for quicker canopy regeneration in cases of canopy breakage [24]. Like the rays and periderm, dilatation is also positively controlled by ethylene [20]. ...
The bark fulfils several essential functions in vascular plants and yields a wealth of raw materials, but the understanding of bark structure and function strongly lags behind our knowledge with respect to other plant tissues. The recent technological advances in sampling and preparation of barks for anatomical studies, along with the establishment of an agreed bark terminology, paved the way for more bark anatomical research. Whilst datasets reveal bark's taxonomic and functional diversity in various ecosystems, a better understanding of the bark can advance the understanding of plants' physiological and environmental challenges and solutions. We propose a set of priorities for understanding and further developing bark anatomical studies, including periderm structure in woody plants, phloem phenology, methods in bark anatomy research, bark functional ecology, relationships between bark macroscopic appearance, and its microscopic structure and discuss how to achieve these ambitious goals.
... Several studies have suggested that suppressed buds can be trapped or engulfed within bark (e.g. references in Lev-Yadun and Aloni 1993;Colin et al. 2010Colin et al. , 2012Burrows 2013) and thus be prevented from resprouting. In Q. suber the bark has been recorded reaching a thickness of 20 cm (Pausas et al. 2009) and even in trees at the end of the cork harvest cycle (9-12 years) the bark on the trunk can be around 3 cm thick, which is much thicker than most trees. ...
Key message
Cork oak has buds protected by the full thickness of its substantial phellem, thus explaining why it is the only European tree that can epicormically resprout after higher intensity fire.
Abstract
Epicormic resprouting has various ecological advantages over basal resprouting. However, after higher intensity fires epicormic resprouting is rare as it is difficult for trees and shrubs to keep both their buds and vascular cambia alive. Quercus suber (cork oak) is the only European tree that can resprout epicormically after higher intensity fires. Q. suber develops very thick bark and it has been assumed, without anatomical evidence, that the bark protects the epicormic buds. We investigated if developmental anatomy could explain why Q. suber is an excellent post-fire epicormic resprouter. We examined buds from mature Q. suber trees, macroscopically using a stereo microscope and microscopically using semi-thin microtome sections. Q. suber produced buds in the foliage leaf axils and the bud scale axils. With the commencement of extensive phellem (cork) production the base of the epicormic buds remained at, or just below, the level of the phellogen and thus cork began to bury the buds, although a narrow tube connected each bud to the bark surface. Q. suber epicormic buds became deeply buried in the phellem and would be protected from heat by the full phellem thickness. With its rapid and substantial development of phellem Q. suber had well-protected epicormic buds even in relatively small diameter stems. These results provide the anatomical evidence to show why Q. suber is a noted epicormic resprouter after crown fire.
... We predicted that smooth-textured bark hinders the ability of bark beetles to land on or crawl upon a tree's stem and tested two related hypotheses: (i) bark surface texture influences bark beetle attack locations and attack density on pine trees and (ii) bark texture affects bark beetles' ability to grip a tree's surface. We also predicted that smooth-textured bark is more common in younger/smaller trees as reported for bark texture in other tree species (Whitmore 1963;Lev-Yadun & Aloni 1993;Biswas & Johri 1997;Friedel et al. 2006) and as also reported for a number of antiherbivore defences in numerous plant species (Boege & Marquis 2005). Thus, we tested a third hypothesis: (iii) bark texture (roughness) increases with increasing tree size (as a correlate of age). ...
... These results suggest an effect of age-related or growth-related factors on bark texture in P. flexilis. Similar changes in bark texture with stages of ontogeny have been described for other deciduous (Lev-Yadun & Aloni 1993;Pinard & Huffman 1997;Friedel et al. 2006) and coniferous species (Biswas & Johri 1997;Malone & Liang 2010). We found the defence offered by smooth bark against bark beetles is greatest for smaller trees, but is retained into trees that are, respectively, large in size (approximately 30 cm in diameter; Fig. 5) in our study systema subalpine forest with short growing seasons and slow tree growth (Mitton & Ferrenberg 2012;Duhl et al. 2013;Ferrenberg, Kane & Mitton 2013). ...
1. Smooth bark on trees and shrubs was historically hypothesized to be an anatomical defense against epiphytic vegetation and phytophagous insects. This hypothesis has fallen from favor, yet no clear tests of bark texture as a defense against insects have been published.
2. We tested the smooth-bark-defense hypothesis using bark beetles specialized to attack pine trees as model insects, and Pinus flexilis (limber pine)—a widespread tree that can have both smooth- and rough-bark surfaces on the same stem—as the model tree. We investigated the effects of bark texture on the locations of bark beetle attacks on trees with a combination of field surveys and experiments in the Colorado Rocky Mountains, USA.
3. Bark beetle attacks were overwhelmingly located on rough bark surfaces and virtually absent from smooth bark. Increasing proportional coverage by smooth bark was negatively related to bark beetle attacks/m2 of bark surface. Experimental tests of bark beetle ability to grip smooth versus rough bark revealed that bark beetles have difficulty gripping and quickly fell from smooth bark but not from rough bark.
4. Smooth bark was negatively related to increasing tree size, but our models indicated that even partial coverage by smooth bark on a tree's trunk can significantly reduce total bark beetle attacks—this reduction likely improves tree fitness as bark beetles must aggregate to overcome tree defenses.
5. Synthesis. Our results indicate that smooth bark on trees can act as an anatomical defense against insects by reducing their ability to grip a tree's surface−even for insects specialized to attack tree stems. Similar to other forms of anti-insect defense (i.e. secondary chemistry, leaf toughness) smooth bark appears to be influenced by plant ontogeny whereby younger trees have greater defenses than older trees. Understanding the adaptive significance of bark texture will require continued field and genetic study. Nevertheless, our results revealed that smooth bark texture increases tree resistance to phytophagous insects calling for the resurrection and vetting of the smooth-bark-defense hypothesis.
... Therefore, it was proposed that the basipetal polar auxin transport inhibits cork formation in these regions (Lev-Yadun and Aloni, 1990). These cork-free regions later enable suppressed buds to develop quickly and form new branches after damage to the canopy, and not to be disturbed by a heavy, hard layer of cork (Lev-Yadun and Aloni, 1993). See also: Plant Growth Factors and Receptors Dilatation When trees and shrubs or even thick annuals grow in diameter, the outer tissues expand to a certain but limited degree. ...
Eucalypts encounter a wide range of severe disturbances such as extensive defoliation by insects, major structural damage from cyclonic winds, as well as foliage and bark loss during drought and fire. Most healthy, mature eucalypts are not killed by these events, but regenerate vegetatively. With increasing intensity of disturbance, resprouting first occurs from the accessory buds in the small-diameter branchlets of the crown, followed by the epicormic buds in the medium- and large-diameter branches and stems, and then from the buds of the lignotuber. All these modes of regeneration are ultimately dependent on preventitious buds and, thus, the present review concentrates on axillary buds, their subsequent development into epicormic or lignotuber buds and their degree of protection from fire. The eucalypts have remarkably abundant, well protected and anatomically distinctive bud-forming structures in their leaf axils, branches, stems and lignotubers. These structures are quite consistent across this large genus, but are generally different from resprouting structures in many other plants. From an anatomical perspective, these structures seem best adapted to regeneration after fire, rather than damage from insects, storms or drought and this also correlates with ecological observations. On a worldwide basis, the eucalypts are some of the most successful post-fire resprouters, especially epicormic resprouting after medium- and high-intensity fires. Given the apparent ecological advantages of epicormic resprouting (the rapid reestablishment of extensive leaf area while simultaneously shading basal resprouters and seedlings) this could be an important factor in the success of eucalypts in Australia. Recent phylogenetic analysis has indicated a long relationship between eucalypts, fire and bud structures that facilitate resprouting.
