scholarly journals Role of Cytokinin in Differentiation of Secondary Xylem Fibers

1982 ◽  
Vol 70 (6) ◽  
pp. 1631-1633 ◽  
Author(s):  
Roni Aloni
Keyword(s):  
Secondary Xylem ◽  
Xylem Fibers

Regeneration of vascular tissue through redifferentiation of interxylary phloem after complete girdling in Aquilaria sinensis

IAWA Journal ◽  
2021 ◽  
pp. 1-16
Author(s):  
Bei Luo ◽  
Arata Yoshinaga ◽  
Tatsuya Awano ◽  
Keiji Takabe ◽  
Takao Itoh
Keyword(s):  
Time Course ◽  
Potential Role ◽  
Vascular Tissue ◽  
Secondary Xylem ◽  
Vascular Cambium ◽  
Aquilaria Sinensis ◽  
Phloem Fibers ◽  
Interxylary Phloem ◽  
Time Course Study

Abstract We studied the time-course of stem response for six months following complete girdling in branches of Aquilaria sinensis to determine the potential role of interxylary phloem (IP) in this response. It was found that the vascular cambium, as well as its derivative secondary xylem and phloem, regenerated fully through redifferentiation of IP. We confirmed that vascular cambium regenerated within one month after girdling based on observation of new vessels, IP, and secondary phloem fibers. The time-course study showed that IPs made connections with each other, merged, and became larger through the proliferation of IPs parenchyma cells and the cleaving of secondary xylem in a narrow zone 400 to 1000 μm deep inside the girdled edge. This led to the formation of a complete circular sheath of vascular cambium, followed by the regeneration of vascular tissue. It is worth noting that the secondary xylem is regenerated always following the formation of a thick belt of wound xylem.

Characters and origin of vessels with heterogenous structure in leaf and flower abscission zones

1999 ◽  
Vol 77 (2) ◽  
pp. 253-261 ◽  
Author(s):  
JP André ◽  
A M Catesson ◽  
M Liberman
Keyword(s):  
Cell Differentiation ◽  
Lycopersicon Esculentum ◽  
Secondary Xylem ◽  
Abscission Zone ◽  
Leaf Abscission ◽  
Cell Maturation ◽  
Casting Method ◽  
Plant Organs ◽  
Flower Abscission

The lifetime of many plant organs does not exceed a few weeks or a few months. These organs separate from the plant at the level of specialized abscission zones. The observation of xylem vasculature in abscission zones, a largely neglected subject, revealed original features when a vessel casting method was used. In all species of dicotyledons examined so far, flower and leaf abscission zones possessed heterogenous metaxylem vessels adjoining protoxylem and secondary xylem vessels with homogenous patterns of lignified thickenings. Heterogenous metaxylem vessel thickenings were helical, reticulate, or scalariform elements when in the abscission zone and pitted elements on the proximal and the distal sides. The origin and possible role of these vessels are considered. Data obtained on the flower abscission zone of tomato (Lycopersicon esculentum Mill.) suggest that formation of heterogenous vessels results from localized changes in the rhythm of cell differentiation and cell maturation inside the procambium-cambium continuum.Key words: abscission zone, cambium, differentiation, heterogenous vessels, procambium, vessel cast.

Laticifers of Ficus Carica and Their Potential Role in Plant Defense

IAWA Journal ◽  
2014 ◽  
Vol 35 (2) ◽  
pp. 109-115 ◽  
Author(s):  
C. Kajii ◽  
T. Morita ◽  
K. Kuroda
Keyword(s):  
Potential Role ◽  
Secondary Xylem ◽  
Nile Blue ◽  
Ficus Carica ◽  
Secondary Phloem ◽  
Fast Green ◽  
Cambial Zone ◽  
A Current ◽  
Latex Production

The distribution and structure of laticifers in Ficus carica L. were investigated in a current-year branch and an 8-year-old trunk, using serial sections stained with safranin-fast green or nile blue. In the 8-year-old trunk, laticifers were found not only in the cortex, secondary phloem, and pith, but also in the secondary xylem. The laticifers in the phloem and xylem were of the branched, non-articulated type. In addition, horizontal laticifers extending from the phloem through the cambium to the xylem were found in some rays. Laticifers penetrating the cambial initial layer elongated in the cambial zone without cell division. Activation of latex production occurred after wounding of cortex and phloem, and the latex exuded from the cut site of laticifers into the surrounding wounded tissue and broken cells. The potential role of laticifers in defense of F. carica against certain pathogens is discussed.

Ontogeny of the protophloem fibers and secondary xylem fibers within the stem of Coleus. II. An electron microscope study

1975 ◽  
Vol 53 (16) ◽  
pp. 1672-1697 ◽  
Author(s):  
Thompson Demetrio Pizzolato ◽  
Charles Heimsch
Keyword(s):  
Secondary Wall ◽  
Secondary Xylem ◽  
Ultrastructural Changes ◽  
Wood Fibers ◽  
Wall Formation ◽  
Phloem Fibers ◽  
Membrane Bound ◽  
Secondary Wall Formation ◽  
Pass Through ◽  
Xylem Fibers

Ultrastructural changes within the protophloem fibers and secondary xylem fibers accompany their ontogeny in the Colens stem. The plasmalemma of both fibers portrays a gently undulating pattern against the wall before secondary wall formation. Commonly a narrow, hyaline region separates the primary wall and the plasmalemma. Fibrillar material arising from the plasmalemma is condensed in the wall. With the onset of secondary wall formation, undulation of the plasmalemma increases. Many microtubules traverse the membrane and are modified into extracytoplasmic microtubules. Vesicles produced by the dictyosomes and endoplasmic reticulum (ER) pass through or fuse with the plasmalemma. These processes abate after the initiation of the secondary wall. Cisternal, vesicular, and tubular forms of ER, the latter a rare form in wood fibers, fluctuate in amount during ontogeny. Mitochondria increase in number by fission and change in size and cristae volume. Microbodies are common in the youngest phloem fibers but are absent from the xylem initials. Microbodies arising as swellings of ER cisternae are numerous after secondary wall formation is underway in both fibers. Microfilaments are rare in wood fibers but are common in young phloem fibers. Spherosomes, which originate from ER cisternae, disappear during the initiation of the secondary wall. Phloem fiber plastids increase in number by either constriction or concentralization until shortly after the start of secondary wall formation. The plastids of the xylem fibers differ from those of the phloem fibers since the organelles contain phytoferritin and large starch grains initially, divide only by constriction, and do not form membrane-bound bodies.

Bm-miR172c-5p regulates lignin biosynthesis and secondary xylem thickness by altering Ferulate 5 hydroxylase gene in Bacopa monnieri

2021 ◽  
Author(s):  
Gajendra Singh Jeena ◽  
Ashutosh Joshi ◽  
Rakesh Kumar Shukla
Keyword(s):  
Drought Stress ◽  
Target Genes ◽  
Secondary Xylem ◽  
Lignin Biosynthesis ◽  
Small Rna Sequencing ◽  
Cleavage Sites ◽  
Environmental Condition ◽  
Cycloartenol Synthase ◽  
Root Tissues

Abstract MicroRNAs (miRNAs) are small non-coding, endogenous RNAs containing 20–24 nucleotides that regulate the expression of target genes involved in various plant processes. A total 1429 conserved miRNA belonging to 95 conserved miRNA families and 12 novel miRNAs were identified from B. monnieri using small RNA sequencing. The Bm-miRNA target transcripts related to the secondary metabolism were further selected for validation. The Bm-miRNA expression in shoot and root tissues were negatively correlated with their target transcripts. The Bm-miRNA cleavage sites were mapped within the coding or untranslated (UTR) region as depicted by the modified RLM-RACE. In the present study, we validate three miRNA targets, including Asparagine synthetase, Cycloartenol synthase, and Ferulate 5 hydroxylase and elucidate the regulatory role of Bm-miR172c-5p, which cleaves the F5H gene involved in the lignin biosynthesis. Overexpression of Bm-miR172c-5p precursor in B. monnieri suppress F5H gene, leading to reduced lignification and secondary xylem thickness under control and drought stress. In contrast, overexpression of target mimics (eTMs) showed enhanced lignification and secondary xylem thickness leading to better physiological response under drought stress. Taken together, we suggest that Bm-miRNA172c-5p might be a key player in maintaining the native phenotype of B. monnieri under control and different environmental condition.

The role of senescence‐associated gene101 ( PagSAG101a ) in the regulation of secondary xylem formation in poplar

2021 ◽  
Author(s):  
Hui He ◽  
Xue‐Qin Song ◽  
Cheng Jiang ◽  
Ying‐Li Liu ◽  
Dian Wang ◽  
...  
Keyword(s):  
Secondary Xylem ◽  
Xylem Formation

scholarly journals Development of Inverse Cambia and Structure of Secondary Xylem in Ipomoea turbinata (Convolvulaceae)

2017 ◽  
Vol 62 (1) ◽  
pp. 87-97
Author(s):  
Kishore S. Rajput
Keyword(s):  
Tropical Forests ◽  
Structural Transformation ◽  
Growth Pattern ◽  
Functional Role ◽  
Secondary Xylem ◽  
Experimental Studies ◽  
Secondary Phloem ◽  
Successive Cambia ◽  
Parenchyma Cells

AbstractStructural transformation of mechanical tissues during the shift from a freestanding to a climbing habit is a characteristic of lianas, which are increasingly abundant in tropical forests. The modification of mechanical tissue and the evolution of a new growth pattern serve to increase stem flexibility and conductive efficiency. In Ipomoea turbinata Lag. (Convolvulaceae), the stem thickens via the formation of two distinct types of successive cambia: functionally normal successive cambia (producing xylem centripetally and phloem centrifugally), and inverse cambia (producing xylem centrifugally and phloem centripetally). The former originates from pericyclic derivatives (parenchyma cells located outside the primary phloem), while the latter originates from the conjunctive parenchyma located on the inner margin of the secondary xylem formed from vascular cambium. The secondary xylem produced by normal cambia is significantly more abundant than the xylem formed by inverse cambia. During primary growth, intraxylary primary phloem differentiates concomitantly with the protoxylem at the periphery of the pith; additional intraxylary secondary phloem is added from adjacent parenchyma cells as the plant ages. During initiation of every successive cambium, middle cells in the meristem give rise to cambium, and cells on either side of it serve as sites for initiation of future cambia. The functional role of inverse cambia remains unknown and awaits further experimental studies.

scholarly journals Development of successive cambia and structure of the secondary xylem in some members of the family Amaranthaceae

2019 ◽  
Vol 6 (1) ◽  
pp. 31-39 ◽  
Author(s):  
Ravindra A. Shelke ◽  
Dhara G Ramoliya ◽  
Amit D Gondaliya ◽  
Kishore S. Rajput
Keyword(s):  
Secondary Wall ◽  
Secondary Xylem ◽  
Secondary Phloem ◽  
Successive Cambia ◽  
The Family ◽  
Parenchyma Cells ◽  
Plant Habit ◽  
Cambial Cells ◽  
Gomphrena Celosioides ◽  
Xylem Fibers

Young stems of Aerva javanica (Burm.f.) Juss. ex Schult., A. lanata (L.) Juss. ex Schult, A. monsonia Mart., A. sanguinolenta (L.) Blume, Alternanthera bettzickiana (Regel) G. Nicholson, A. philoxeroides (Mart.) Griseb., Gomphrena celosioides Mart., G. globosa L. and Telanthera ficoidea (L.) Moq., showed the renewal of small sectors of cambium by replacing with new segments. Therefore, the secondary phloem formed by earlier cambial segments form isolated islands of phloem enclosed within conjunctive tissues became embedded in the secondary xylem. As the stem grows older, complete ring of cambium is renewed; sometimes an anastomosing network of successive cambia may be seen due to the renewal of larger segments of the cambium. Renewal of the cambium takes place by repeated periclinal division in the parenchyma cells positioned outside to the phloem formed by the previous cambium. Functionally the cambium is bidirectional and exclusively composed of fusiform cambial cells. Differentiation of conducting elements of the secondary xylem and phloem remains restricted to the certain cambial cells while rest of the segments exclusively produce conjunctive cells. Accumulation of starch along with the presence of nuclei in the xylem fibers even after deposition of the secondary wall is consistent in all the species and it seems to be associated with the absence of rays in the secondary xylem and phloem of nine species from four genera. The significance of successive cambia, rayless xylem and nucleated xylem fibers were correlated with plant habit.

Role of Growth Regulators in Initiation of Secondary Xylem and Phloem Cells

1979 ◽  
Vol 140 (1) ◽  
pp. 20-24 ◽  
Author(s):  
Marcia A. Harrison ◽  
Richard M. Klein
Keyword(s):  
Growth Regulators ◽  
Secondary Xylem
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