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"Stems (Botany)"
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\"This title provides curious young readers with a close-up look at plant stems. Readers will discover why plants need stems, the different kinds of stems, and how new plants can grow from the stems of mature plants.\"--Amazon.com.
Book
Heartwood Relationship with Stem Diameter in IPinus canariensis/I Plantations of Gran Canaria, Spain
The development of stem heartwood and the factors that control it play an important role in tree physiology, thereby impacting demographic and ecological processes of woody species. We investigated the relationships of stem heartwood with site- and tree-level variables in Pinus canariensis plantations. A total of 30 plots were sampled in the island of Gran Canaria, Spain, over a large elevation range (995–1875 m) and on terrain with different slopes (4%–70%) and exposures. The 15 pines closest to each plot center were measured and cored to quantify growth rates and the size of heartwood, also known as “tea”. We used generalized linear mixed models (GLMMs) to account for both fixed and random effects while evaluating the best predictors of heartwood presence. Stem diameter was the variable most correlated with heartwood radius, and allowing for a random slope and intercept of this relationship accounted for spatially related variability. Furthermore, the GLMM model became more effective when the relationship between stem diameter and heartwood was modeled using the presence/absence of the “tea” rather than its measured size. Other site- and tree-level variables either were not statistically significant or improved the model relatively little. Because stem heartwood affects both wood quality and the amount of carbon that trees can store, our findings have implications for forest management and carbon-conscious policies.
Journal Article
Assessment of Physical and Mechanical Properties Considering the Stem Height and Cross-Section of IPaulownia tomentosa/I Wood
The aim of this study is to analyze the properties of Paulownia tomentosa x elongata plantation wood from Serbia, considering the influence of the stem height (0 to 1 m and 4.5 to 6 m above soil level—height spot) and radial position from the pith to bark (in the core, near the bark, and in between these zones—cross-section spot). The results show that most properties are improved when the samples were taken from upper parts of the tree (height spot) and from the near bark spot (cross-section spot). The mean density measured 275 kg/m[sup.3] at the stem height between 4.5–6 m and 245 kg/m[sup.3] for the samples collected from 0–1 m trunk height. The density had the highest value on the spot near bark (290 kg/m[sup.3]), for the mature wood at a height of 4.5–6 m, and near pith had a mean density of 230 kg/m[sup.3]. The Brinell hardness exhibited highest values in the axial direction (23 N/mm[sup.2]) and near bark (28 N/mm[sup.2]). The bending strength was 41 N/mm[sup.2] for the trunk’s height range of 4.5–6 m and 45 N/mm[sup.2] in the cross-section, close to cambium. The three-point modulus of elasticity (MOR) of the samples taken at a stem height of 4.5 to 6 m was up to 5000 N/mm[sup.2], and on the spot near bark, the MOR measured 5250 N/mm[sup.2]. Regarding compressive strength, in the cross-section, near the pith, the mean value was the highest with 23 N/mm[sup.2] (4.5–6 m), whilst it was 19 N/mm[sup.2] near bark. The tensile strength was, on average, 40 N/mm[sup.2] for both 0–1 m and 4.5–6 m trunk height levels and 49 N/mm[sup.2] between bark and pith. The screw withdrawal resistance measured 58 N/mm for the samples extracted at a stem height of 4.5 to 6 m and 92 N/mm for the specimens collected near pith. This study stresses the influence, in short-rotation Paulownia timber, of indicators, such as juvenile and mature wood (difference emphasized after the fifth year of growth) and height variation, on the physical and mechanical properties of sawn wood. This study will help utilize more efficient sustainable resources, such as Paulownia plantation wood. This fast-growing hardwood species from Europe is adequate as a core material in sandwich applications for furniture, transport, sport articles, and lightweight composites, being considered the European Balsa.
Journal Article
Effect of Rhizome Fragment Length and Burial Depth on the Emergence of a Tropical Invasive Weed ICyperus aromaticus/I
Cyperus aromaticus (Navua sedge) is a problematic perennial weed in pastures and crops including sugarcane, banana, rice, and fruits and vegetables in tropical climates. It reproduces both via rhizomes and seeds. As a regenerative and storage organ, these rhizomes play an important part in the invasion, establishment, and persistence of this weed. To eliminate their regenerative ability, it is important to understand the regrowth potential with respect to rhizome fragment size and burial depth. This study evaluated the emergence of C. aromaticus from rhizomes in a controlled condition. Three different sizes of rhizome fragments were buried at seven depths of up to 20 cm in two soil types. The experimental measurements included (i) the time for tillers to emerge, (ii) the cumulative emergence of tillers, recorded weekly, and (iii) the number of underground emerging tillers. The cumulative shoot emergence and the number of underground tillers produced were found to be positively correlated with the initial length of the rhizome fragments and negatively correlated with the burial depth. The time for the emergence of the tillers was negatively correlated with the burial depth, and soil type had no significant effect on any of the parameters recorded. There was no emergence recorded from rhizomes buried at 15 cm depth and deeper, irrespective of their size. Our results indicate that the combination of the fragmentation of rhizomes into small pieces and a deep burial, below 15 cm, is an important aspect to control the regeneration of C. aromaticus from rhizomes, if tillage is carried out, and can therefore form a part of an integrated weed management strategy for this troublesome weed.
Journal Article
Form and Volume of the Stem of ITectona grandis/I L.f. in the Central-WESTERN Region of Brazil
The international market has recognized the high value of Tectona grandis L.f. plantations, requiring the development of reliable and accurate tools and techniques to quantify forest stocks accurately. In this study, we developed suitable equations to estimate the stem diameters and volume of Tectona grandis trees in the central-western region of Brazil, evaluating the stem form change points (FCPs) and testing the stratification of data as a measure to control their variation. The Schöepfer model was tested in the study of the FCPs of the stem, and single equation, segmented and variable-exponent taper functions were used to describe the stem profile. After the selection of the model for the taper, data stratification in the DBH classes, form parameter “r” and artificial form factor were proposed. The total volumes of each tree were calculated by integrating the Clark III et al. model. The FCPs of the Tectona grandis stems occurred at 28%, 57% and 73% of the total height, corresponding, on average, to the absolute positions of 6.4 m, 13.3 m and 16.5 m. The Clark III et al. equation, without stratification, was the most appropriate equation to estimate the diameters along the stem and the volume of Tectona grandis trees in the central-western region of Brazil.
Journal Article
High-resolution transcriptomics of stem and storage root vascular cambia highlight regulatory processes for xylem parenchyma differentiation in cassava
Due to their high carbohydrate content, the storage roots of cassava are an important food source for hundreds of millions of people worldwide. In contrast to the woody stems of the plant, the xylem of the storage roots produces mainly starch-rich storage parenchyma cells and only few tracheary elements and almost no fibers. Despite these obvious differences, both stems and storage roots are formed by a vascular cambium. To find more insights into the differences in the regulation of cell division and differentiation in stems and storage roots, a cryo-sectioning approach was utilized, to generate high-resolution transcriptome profiles spanning the entire vascular cambium of both tissues. We observed that storage parenchyma formation is connected to the repression of secondary cell wall formation through a decrease in expression levels of key players in the NAC/MYB regulatory network, as well as decreases in the downstream pathways for lignin and hemicellulose biosynthesis. Additionally, the expression of
MeWOX14
, a transcription factor associated with GA signaling and xylem fiber differentiation, is strongly reduced in storage roots compared to stem xylem. By contrast, the expression of
MeKNOX1
, a well-known meristem regulator, as well as most cassava
LSH
genes and several ABA-related transcription factors were associated with parenchyma cells. Our data suggest that the repression of secondary cell wall formation and GA signaling, together with an active auxin and ABA signaling, as well as extended
MeKNOX1
activity are associated with storage parenchyma formation in cassava storage roots.
Journal Article
Polyphenolic Characterization, Antioxidant, Antihyaluronidase and Antimicrobial Activity of Young Leaves and Stem Extracts from IRubus caesius/I L
Fruits are the main food part of the European dewberry (Rubus caesius L.), known as a source of polyphenols and antioxidants, while very little attention is paid to leaves and stems, especially young first-year stems. The purpose of this work was to analyze for the first time water and ethanol extracts obtained from young, freshly developed, leaves and stems of the European dewberry to determine their antioxidant and biological activity, whereas most of the papers describe biological properties of leaves collected during summer or autumn. As the phytochemical profile changes during the growing season, the quantitative and qualitative content of flavonoid glycosides and flavonoid aglycones was analyzed using reversed phase liquid chromatography/electrospray ionization triple quadrupole mass spectrometry (LC-ESI-MS/MS) with multiple reaction monitoring (MRM). The ability to inhibit hyaluronidase as well as antioxidant activity (2,2 diphenyl-1-picrylhydrazyl: DPPH and ferric antioxidant power: FRAP) were estimated. Extracts were also analyzed against Gram-positive and Gram-negative bacteria. The results of the qualitative phytochemical analysis indicated the presence of flavonoid aglycones and flavonoid glycosides, with the highest amount of tiliroside, hyperoside, isoquercetin, astragalin, rutin and catechin in ethanol extracts. DPPH and FRAP tests proved the high antioxidant activity of the extracts from leaves or stems and the antihyaluronidase assay revealed for the first time that water and ethanol extracts obtained from the stems exhibited the ability to inhibit hyaluronidase activity resulting in an IC[sub.50] of 55.24 ± 3.21 and 68.7 ± 1.61 μg/mL, respectively. The antimicrobial activity has never been analyzed for European dewberry and was the highest for Clostridium bifermentans and Clostridium sporogenes—anaerobic sporulation rods as well as Enterococcus faecalis for both water and ethanol extracts.
Journal Article