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Arrangement and morphology of the xylem conduits in trunk of D. draco. a Cross-section, 60 µm-thick, stained with toluidine blue and safranin (1:1). Lignified cell walls stained in red. b Collateral primary bundle. c Amphivasal secondary bundles. d–f Scanning electron microscope (SEM) views of PC. g SEM view of part of the cell wall of SC. h–i Part of cell walls of SC in a radial section (light microscope). F fibers, H helical cell wall thickenings, P pitted cell wall, PC primary conduit, PH phloem, PP primary ground parenchyma, R reticulate cell wall thickenings, S scalariform perforation plate, SC secondary conduit, SH slender helical cell wall thickenings, SP secondary ground parenchyma
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Main conclusion
In Dracaena draco trunks, the primary and secondary xylem conduits co-function. Both are resistant to embolism; however, secondary conduits are mainly involved in mechanical support.
Abstract
Monocotyledonous dragon trees (Dracaena spp., Asparagaceae) possess in their trunks both primary and secondary xylem elements, organized into...
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Citations
... Various types of secondary growth have emerged during evolution. A special type of secondary growth has appeared in some monocotyledons, which is a manifestation of the activity of the monocot cambium producing secondary xylem along with secondary phloem in the form of vascular bundles (Carlquist, 2012;Madeřa et al., 2020;Jura-Morawiec et al., 2021;Tulik et al., 2022). Another product of the monocot cambium is the parenchyma, the cells of which fill the space between the vascular bundles and constitute a large part of the secondary growth (Hubaĺkováet al., 2017). ...
The evolution of the vascular system has led to the formation of conducting and supporting elements and those that are involved in the mechanisms of storage and defense against the influence of biotic and abiotic factors. In the case of the latter, the general evolutionary trend was probably related to a change in their arrangement, i.e. from cells scattered throughout the tissue to cells organized into ducts or cavities. These cells, regardless of whether they occur alone or in a cellular structure, are an important defense element of trees, having the ability to synthesize, among others, natural resins. In the tracheid-based secondary xylem of gymnosperms, the resin ducts, which consist of secretory cells, are of two types: axial, interspersed between the tracheids, and radial, carried in some rays. They are interconnected and form a continuous system. On the other hand, in the tracheid-based secondary xylem of monocotyledons, the resin-producing secretory cells do not form specialized structures. This review summarizes knowledge on the morpho-anatomical features of various types of resin-releasing secretory cells in relation to their: (i) location, (ii) origin, (iii) mechanism of formation, (iv) and ecological significance.
... Based on the IUCN Red List, many dragon tree species belong to the endangered category [6]. In addition, Dracaena species are monocotyledonous plants [4,10]; however, they differ in the present monocot cambium [10], which causes secondary thickening of stems and branches [10,11]. They are also well known for their red resin, which is also known as dragon's blood and was used as a medicine in ancient times [5,6,12]. ...
... Based on the IUCN Red List, many dragon tree species belong to the endangered category [6]. In addition, Dracaena species are monocotyledonous plants [4,10]; however, they differ in the present monocot cambium [10], which causes secondary thickening of stems and branches [10,11]. They are also well known for their red resin, which is also known as dragon's blood and was used as a medicine in ancient times [5,6,12]. ...
... Based on the IUCN Red List, many dragon tree species belong to the endangered category [6]. In addition, Dracaena species are monocotyledonous plants [4,10]; however, they differ in the present monocot cambium [10], which causes secondary thickening of stems and branches [10,11]. They are also well known for their red resin, which is also known as dragon's blood and was used as a medicine in ancient times [5,6,12]. ...
Background: Dracaena cinnabari is a monocot species that does not form annual tree rings; thus, its age can only be estimated. This species is threatened by low natural regeneration, with an evident absence of younger individuals most likely caused by overgrazing; therefore, knowing trees’ ages is important for possible conservation strategies; Methods: Data collection was conducted on the Firmihin Plateau on Socotra Island (Yemen) in 2021, and the diameter at breast height (DBH) of 1077 individuals was measured, the same as those established on monitoring plots 10 years before the current measurement. The 10-year radial stem increment and DBH obtained in 2011 served as a basis for the linear model from which the equations for the age calculation were derived. Results and Conclusions: A direct model of age estimation for D. cinnabari was developed. According to the fit model, the age in the first (10.1–15 cm) DBH class was estimated to be 111 years, while that in the last DBH class (90.1–95 cm) was estimated to be 672 years. The results revealed that the previously used indirect methods for D. cinnabari age estimation were accurate.
Dracaena cambodiana Pierre ex Gagnep is an important plant resource for producing dragon's blood and one of most popular ornamental trees in China. For a better understanding of the physiological function of the stem, the structural characteristics and main substance histological location of the stems of D. cambodiana were studied. The structural characteristics of the different developmental stages of stems of D. cambodiana were observed and described detailly. And then a schematic diagram of the mature stem was created. Histochemical staining showed that two kinds of polysaccharides distributed in parenchymal cells. Saponins distributed mainly in ground tissue and phenolic compounds distributed mainly in the thick cell walls. An abundant of calcium oxalate raphide bundles were identified in cortex and primary tissue. Finally, the role of the above results in the taxonomy of Dracaena species and in their strong adaptability was discussed.
