Girdling was carried out by removing a bark strip 1. Sectioning was performed at 15 cm away from the base of the trees with a sharp knife.
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Results Responses of Hymenaea courbaril and Esenbeckia febrifuga Fig. Individuals of Hymenaea courbaril did not resprout from roots, independently of treatment. On the other hand, Esenbeckia febrifuga originated several suckers from roots when the main trunk was removed Fig. Six of 11 individuals of E. Shoots developed on several lateral roots, totalizing 89 suckers Sometimes, there was a thickening of root on the distal portion of the root sucker.
From 11 individuals with lateral roots sectioned, six resprouted from roots, totalizing 30 sucker sprouts.
These suckers were formed generally on the proximal end of the sectioned root, that is, in the side next to the main tree, and, occasionally, along the roots. The average diameter of the roots was 1. These sprouts might develop individually or in clusters. Individuals of Esenbeckia febrifuga showed no sucker sprout originated on roots from individuals with girdled or intact lateral roots control.
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All studied species produced buds on root cuttings but the mode of bud origin varied among them. Initially, there was a thickening of certain areas of the root cuttings of Bauhinia forficata and, later, buds emerged through the bark. The gap formed in this region of the root cutting Fig. The outer cells of the exposed secondary xylem were ruptured or obliterated in this region.
- Meaning of "laurina" in the Portuguese dictionary.
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Accumulation of substances inside vessel elements below them could be observed and the tylose formation was intensified Fig. Healing phellogen developed only in the cut edges of the bark bounding the wounded secondary phloem and became continuous with the phellogen of original periderm of intact areas of the root. The vascular cambium cells next to the gap divided to form a small callus with cells of different size and shape Fig.
The vascular cambium was restored from the differentiation of the callus cells in some areas of the root and became continuous with the vascular cambium of intact areas. Root fragments of Bauhinia forficata collected at random from the field Fig. Parenchymatic cells of the secondary phloem on the opposite side of the original periderm elongated and divided to form a callus Fig. Buds developed exogenously at the periphery of the callus Fig. Vascular nodules were formed next to the site of bud emergence and were constituted by the cylindrical vascular cambium producing phloem to the outside and xylem to the inside part of the ring.
The vascular connection between bud and callus was made via this nodule Fig. Centrolobium tomentosum buds devel oped near the vascular cambium Fig.
Synonyms and antonyms of laurina in the Portuguese dictionary of synonyms
The differentiation of the vascular tissues between the bud and root was acropetal in C. The acropetal differentiation was due to meristem formation which was named as vascular connection meristem Fig. This meristem was formed near the periphery of wide rays in the secondary phloem, whose dilatation is due to anticlinal cell divisions restricted to bud site Fig. In this dilated area, vascular cambium produced more parenchymatic cells than other cell types in the secondary xylem.
Inga laurina had exogenous buds Fig. These meristemoids were very close to each other Fig.
Vascular tissues developed between bud and root cutting and then the sclerenchymatic ring and periderm were ruptured by the emergence of the bud Fig. It was not possible to verify the direction of vascular differentiation between bud and root cutting in Inga laurina and Bauhinia forficata. Disturbance such as herbivore, fire, floods, hurricanes, landslides, or logging may kill or induce resprouting of woody plants Bond and Midgley after causing damages to aerial or subterranean organs Lacey and Johnston , Paukkonen et al.
The majority of tree species produces secondary trunks only when apical control is destroyed or blocked by some extrinsic factor Del Tredici Even though growth is the result of a complex interaction of auxins and other hormones Schier , heavy root sprouting following lethal aboveground disturbances can be due to the interruption of auxin transport from stems to roots and the subsequent release of buds from hormonal suppression Farmer , Schier Indeed, after collection of root cuttings, auxin levels drop rapidly with time Eliasson , and sucker development can proceed.
Our results support the results found in these studies, because all studied species produced buds on root cuttings and there was a great number of suckering on roots in Esenbeckia febrifuga when the main trunk was cut or when the shallow lateral roots were sectioned.
However, the individuals submitted to the treatment of girdling of the lateral roots did not sprout. According to Jones , auxin transport in root is predominantly down through the central stele and after auxin reaches the root tip, it is distributed back upward along the root in the epidermis and subtending cortical cells. Thus, the removal of the strip of bark has not been efficient to prevent the auxin transport along the root. We believe that Hymenaea courbaril did not produce suckers on roots, as it does in native ecosystems due to the age of individuals. They were in different physiological phases during our observations: According to Zimmerman , flower production is the first sign for adult phase, even though the end of the juvenile phase and the first flowering may not coincide.
This could explain why root sprouting was not observed during the analyzed period, while it is usually observed in adult plants growing in native environment Rodrigues et al. The mode of bud origin on roots varied among the studied species. Buds originated from the callus in Bauhinia forficata and Esenbeckia febrifuga or they developed near the vascular cambium in Centrolobium tomentosum and from the proliferated phloematic parenchyma in Inga laurina.
The callus formation prior to bud origin was also verified in Fagus grandifolia Ehrh. Leguminosae by Hayashi et al. According to Sharples and Gunnery , when the callus extended to fill the wounding region in Hibiscus rosa-sinensis L. In the injured areas of Esenbeckia febrifuga cuttings, callus formation occurred on wounded surface. Nevertheless, these two meristems phellogen and vascular cambium did not regenerate. However, callus filled partially the gap formed in the root bark in Bauhinia forficata cuttings and in some areas the vascular cambium was restored from the differentiation of the callus cells becoming continuous with the cambium of intact areas while the phellogen differentiated only in the cut edges of the bark bounding the wound tissue.
Similar process was observed by Mello et al.
Vascular connection between buds and root cutting of Esenbeckia febrifuga was established by an acropetal and basipetal differentiation of vascular tissues as observed in Machaerium stipitatum Hayashi et al. The acropetal vascular differentiation of E. This dilatation of phloematic ray in E. In the root bark fragments of Bauhinia forficata , the vascular connection between buds and callus occurred by vascular nodules formed next to the site of bud emergence.
All studied species showed reparative root buds, as they were exogenous in origin and did not have bud traces produced in the secondary xylem Bosela and Ewers Reparative buds form de novo in response to senescence, injuries or other types of disturbance of the root, and may therefore be initiated at any period of root secondary growth Bosela and Ewers According to the authors, the presence of additional buds, formed during the early growth of uninjured roots, is a characteristic related to clonal spread.
Therefore, it is possible that individuals of Centrolobium tomentosum in natural conditions produce additional and reparative buds as Penha confirmed young clones through RAPD molecular markers for this species in forest fragments. Thus, the great number of tree species of Leguminosae in forest fragments affected by disturbances can be probably due to their ability of root-sprouting Rodrigues et al. Root suckering promotes vegetative propagation because it allows spreading of individuals from the original site of establishment, promoting the colonization of new sites Bond and Midgley , Del Tredici Therefore, the capacity of producing reparative buds from underground systems, as demonstrated here, shows the vegetative reproduction potential of these species as already discussed by Rodrigues et al.
In addition, it emphasizes its importance in the process of spatial reoccupation of fire events.
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