Structure and ontogeny of the fissured stems of Callaeum (Malpighiaceae)

Stem ontogeny and structure of two neotropical twining vines of the genus Callaeum are described. Secondary growth in Callaeum begins with a typical regular cambium that gradually becomes lobed as a result of variation in xylem and phloem production rates in certain portions of the stem aligned with stem orthostichies. As development progresses, lignified ray cells of the initially formed secondary xylem detach on one side from the adjacent tissues, forming a natural fracture that induces the proliferation of both ray and axial nonlignified parenchyma. At the same time, parenchyma proliferation takes place around the pith margin and generates a ring of radially arranged parenchyma cells. The parenchyma generated in this process (here termed disruptive parenchyma) keeps dividing throughout stem development. As growth continues, the parenchyma finally cleaves the lignified axial parts of the vascular system into several isolated fragments of different sizes. Each fragment consists of xylem, phloem and vascular cambium and is immersed in a ground matrix of disruptive parenchyma. The cambium present in each fragment divides anticlinally to almost encircle each entire fragment and maintains its regular activity by producing xylem to the centre of the fragment and phloem to the periphery. Additionally, new cambia arise within the disruptive parenchyma and produce xylem and phloem in various polarities, such as xylem to the inside and phloem to the outside of the stem, or perpendicularly to the original cambium. Unlike the very distinctive stem anatomical architecture resulting from this cambial variant in Callaeum, its secondary xylem and phloem exhibit features typical of lianas. These features include very wide conducting cells, abundant axial parenchyma, high and heterocellular rays and gelatinous fibres.

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Structure of the secondary xylem and development of a cambial variant in Serjania mexicana (Sapindaceae)

IAWA Journal ◽

10.1163/22941932-bja10075 ◽

2021 ◽

pp. 1-11

Author(s):

Kishore S. Rajput ◽

Amit D. Gondaliya ◽

Roger Moya

Keyword(s):

Secondary Xylem ◽

Secondary Growth ◽

Stem Anatomy ◽

The Family ◽

Ray Cells ◽

Cambial Variant ◽

Proportional Increase ◽

Plant Families ◽

Ray Parenchyma Cells ◽

Cambial Variants

Abstract The lianas in the family Sapindaceae are known for their unique secondary growth which differs from climbing species in other plant families in terms of their cambial variants. The present study deals with the stem anatomy of self-supporting and lianescent habit, development of phloem wedges, the ontogeny of cambial variants and structure of the secondary xylem in the stems of Serjania mexicana (L.) Willd. Thick stems (15–20 mm) were characterized by the presence of distinct phloem wedges and tangentially wide neo-formed cambial cylinders. As the stem diameter increases, there is a proportional increase in the number of phloem wedges and neo-formed vascular cylinders. The parenchymatous (pericyclic) cells external to phloem wedges that are located on the inner margin of the pericyclic fibres undergo dedifferentiation, become meristematic and form small segments of cambial cylinders. These cambia extend tangentially into wide and large segments of neoformations. Structurally, the secondary xylem and phloem of the neo-formed vascular cylinders remain similar to the derivatives produced by the regular vascular cambium. The secondary xylem is composed of vessels (wide and narrow), fibres, axial and ray parenchyma cells. The occurrence of perforated ray cells is a common feature in both regular and variant xylem.

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Development of cambial variant and parenchyma proliferation in Hewittia malabarica (Convolvulaceae) from India and South Africa

IAWA Journal ◽

10.1163/22941932-bja10046 ◽

2020 ◽

pp. 1-14

Author(s):

Kishore S. Rajput ◽

Amit D. Gondaliya ◽

Himansu Baijnath

Keyword(s):

South Africa ◽

Secondary Xylem ◽

Secondary Growth ◽

Stem Anatomy ◽

Histological Techniques ◽

The Family ◽

Ray Cells ◽

Meristematic Activity ◽

Cambial Variant ◽

Interxylary Phloem

Abstract Members of the Convolvulaceae are characterized by the climbing habit and occurrence of variant secondary growth. From a histological perspective, the genus Ipomoea L. is the most extensively studied, while other genera have been less studied. Here, stem anatomy of the least studied genus in the family, Hewittia Wight & Arn., represented by Hewittia malabarica (L.) Suresh was investigated using classical histological techniques. In both the samples collected from India and South Africa, stem thickness increased by developing different types of cambial variants such as: neo-formed vascular cylinders, parenchyma proliferation at the phloem wedges, ray-derived cambia from dilating phloem rays, internal cambium, intra- and interxylary phloem. Neo-formed vascular cylinders develop from the parenchyma cells external to the phloem as a meristemoid in thick stems and later in dilating ray cells. With the increase in stem diameter, cells of the phloem wedges showed proliferation by meristematic activity, which form a connection with the cortex by rupturing the primary tissue ring of eustele. Subsequently, development of cambium in phloem wedges and deposition of its derivatives increased the tangential width of rays. Mature thick stems (25–30 mm) give rise to a fissured stem. Intraxylary (internal) phloem development on the pith margin was observed from primary growth onwards and in thick stems secondary intraxylary phloem developed from the internal cambium. Internal cambium is functionally bidirectional and produces secondary xylem internally and secondary phloem externally. In all the samples, patches of unlignified parenchyma embedded within the secondary xylem dedifferentiate and mature into interxylary phloem with the increasing age. Development of cambial variant and structure of the secondary xylem is correlated with the functional significance of the climbing habit.

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CAMBIAL VARIANT AND XYLEM STRUCTURE IN THE STEM OF COCCULUS HIRSUTUS (MENISPERMACEAE)

IAWA Journal ◽

10.1163/22941932-90000345 ◽

2003 ◽

Vol 24 (4) ◽

pp. 411-420 ◽

Cited By ~ 7

Author(s):

Kishore S. Rajput ◽

K.S. Rao

Keyword(s):

Vascular Bundles ◽

Growth Rings ◽

Xylem Structure ◽

Vessel Elements ◽

Parenchyma Cells ◽

Ray Cells ◽

Cambial Variant ◽

Stem Development ◽

Cambial Cells ◽

Cocculus Hirsutus

Development of cambial variant and xylem structure were studied in the stem of Cocculus hirsutus (Menispermaceae). In the early stages of stem development several collateral vascular bundles are joined by interfascicular cambium resulting in the formation of a complete cambial cylinder. After functioning for two to three years the cambial ring ceases its activity. Subsequently a second ring of cambium is formed from the innermost cortical parenchyma cells. These parenchyma cells undergo periclinal divisions to give rise to cells that become lignified, abaxially, and cambial cells, adaxially. The cambial cells divide periclinally giving rise to individual vascular bundles with xylem and phloem. Later the cambium in each bundle is joined by interfascicular cambium. Subsequent cambia develop similarly resulting in the formation of successive rings of xylem and phloem. During the leafless condition, all the cambial rings are dormant, and flanked by mature xylem and phloem elements. With the sprouting of new leaves, either the existing outermost cambium reactivates or an entire new ring of cambium develops. The xylem is diffuseporous with indistinct growth rings. It is composed of fibre-tracheids, tracheids, vessel elements, libriform fibres, and parenchyma cells. Xylem rays are multiseriate, compound and heterocellular. Deformed libriform fibres and vessel elements commonly occur among the ray cells in all the successive rings of xylem. The length of fibres and the height and width of xylem rays increase gradually from the centre towards the periphery of the stem.

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Structure of Stem and Cambial Variant in Spatholobus Roxburgii (Leguminosae)

IAWA Journal ◽

10.1163/22941932-90001317 ◽

1993 ◽

Vol 14 (2) ◽

pp. 191-204 ◽

Cited By ~ 4

Author(s):

M.N.B. Nair

Keyword(s):

Vascular Tissue ◽

Secondary Growth ◽

Sieve Tube ◽

Secretory Cells ◽

Secondary Phloem ◽

Phloem Parenchyma ◽

Companion Cells ◽

Parenchyma Cells ◽

Ray Cells ◽

Cambial Variant

The stern of Spatholobus roxburghii, a tropicalliana, has alternating layers of xylem and phloem as a result of formation and activity of successive cambia. Successive cambial rings are developed by dedifferentiation of groups of parenchyma cells outside the discontinuous band of sclereid-fibres. The sclereid- fibre band is formed by the development of sclereids between the primary bark fibres. Each successive cambium first produces a layer of sclereid-fibres which separates the vascular tissue produced by one cambial ring from the other. After secondary growth, the epidermis is replaced by periderm. In the older stern phelloderm contributes to the formation of new cambiallayers. Secondary phloem has sieve tube members; companion cells, phloem parenchyma, phloem fibres and secretory cells. The wood shows a tendency towards ring-porosity only in the first xylem layer. The subsequent layers are diffuseporous. The vessels are wide and narrow. Perforated ray cells or radial vessels are frequent in the wood and probably help in vertical conduction by interconnecting vessel endings. In this scandent species parenchyma cells are abundant. It is inferred that they help the vessel segments to remain undamaged when the woody stern twists around supports.

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SECONDARY GROWTH IN THE STEM OF SOME SPECIES OF ALTERNANTHERA AND ACHYRANTHES ASPERA (AMARANTHACEAE)

IAWA Journal ◽

10.1163/22941932-90000257 ◽

2000 ◽

Vol 21 (4) ◽

pp. 417-424 ◽

Cited By ~ 12

Author(s):

Kishore S. Rajput ◽

K.S. Rao

Keyword(s):

Secondary Growth ◽

Sieve Tube ◽

Axial Parenchyma ◽

Achyranthes Aspera ◽

Companion Cells ◽

Cambial Variant ◽

Mother Cells

Secondary growth in Achyranthes aspera, Alternanthera polygamous, A. pungens, A. sessilis, and A. triandra was achieved by the development of a cambial variant resulting in successive rings of xylem and phloem. Each new cambium was developed at a distance about two to three cells external to the phloem produced by the previous cambium. The development of phloem was not synchronous in the species studied. Phloem development started either simultaneously with xylem or after the formation of a few xylem derivatives. In Achyranthes, xylem production started first followed by the development of phloem. Phloem mother cells differentiated into sieve tube elements, companion cells and axial parenchyma. Xylem was storied and exclusively composed of axial elements. Radial elements were absent in all the xylem rings of the stem. Vessels were angular and mostly solitary, but radial and tangential multiples were also observed occasionally. Xylem fibres were nonseptate and nucleated. Development of phloem and the rayless nature of the xylem is discussed.

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Development of successive cambia and wood structure in stem of Rivea hypocriteriformis (Convolvulaceae)

Polish Botanical Journal ◽

10.1515/pbj-2016-0003 ◽

2016 ◽

Vol 61 (1) ◽

pp. 89-98 ◽

Cited By ~ 2

Author(s):

Kishore S. Rajput

Keyword(s):

Secondary Xylem ◽

Monsoon Season ◽

Secondary Growth ◽

Vascular Bundles ◽

Growth Rings ◽

Successive Cambia ◽

Initial Stage ◽

Ray Cells ◽

Cell Layers ◽

Ray Parenchyma Cells

Abstract This study examined the formation of successive rings of cambia in Rivea hypocriteriformis Choisy (Convolvulaceae). The mature stem is composed of four to five rings of xylem alternating with phloem. Successive cambia originate as smaller and larger segments; union and anastomosing of small cambial segments often leads to the formation of discontinuous rings. In the initial stage of growth, several vascular bundles interconnect to form the first ring of vascular cambium. The cambium remains functional for one complete season and becomes dormant during summer; a new ring of cambium is completed prior to the subsequent monsoon season and sprouting of new leaves. Successive cambia are initiated from the pericyclic parenchyma situated three to four cell layers outside of the protophloem. Functionally, all the successive cambia are bidirectional and produce secondary xylem centripetally and phloem centrifugally. The secondary xylem is diffuse-porous, with indistinct growth rings and consisting of wide fibriform vessels, fibre tracheids, and axial and ray parenchyma cells. The xylem rays are uni- to multiseriate and heterocellular. The multiseriate rays contain lignified marginal ray cells and thin-walled, unlignified central cells. The central ray cells also show accumulations of starch and druses. Discrete strands of intraxylary phloem occur at the periphery of the pith, and additional intraxylary phloem develops from adjacent cells as secondary growth progresses. Earlier-formed phloem shows heavy accumulation of callose, followed by its compaction. The development of successive cambia is correlated with extension growth and with the phenology of the plant.

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Stem anatomy at various developmental stages of secondary growth in Turbina corymbosa (Convolvulaceae)

Plant Ecology and Evolution ◽

10.5091/plecevo.2018.1389 ◽

2018 ◽

Vol 151 (2) ◽

pp. 219-230 ◽

Cited By ~ 1

Author(s):

Manoj M. Lekhak ◽

Amit D. Gondaliya ◽

Shrirang R. Yadav ◽

Kishore S. Rajput

Keyword(s):

Secondary Xylem ◽

Secondary Growth ◽

Growth Patterns ◽

Stem Anatomy ◽

Successive Cambia ◽

Background Population ◽

Short Period ◽

Parenchyma Cells ◽

Ray Parenchyma ◽

Ray Parenchyma Cells

Background – Population growth of lianas in the tropical forest is credited to their ability of CO2 sequestration and efficiency of the narrow stems to supply water required for the amount of foliage it bears. Turbina corymbosa (L.) Raf. (Convolvulaceae Juss.) is one of the fast-growing invasive species of scrambling woody lianas. It covers trees entirely within a short period to compete with above-ground resources (particularly sunlight). However, no information is available on how it manages to cope up with an increasing demand of water supply and mineral nutrients. What are the structural and developmental patterns adapted by this species to expand the stem diameter for efficient supply of below-ground resources? Therefore, our aim was to investigate the secondary growth patterns and structure of secondary xylem and phloem in T. corymbosa.Methods – Several samples of the stem with various diameters were studied using a histological method. Morphological and anatomical analyses were carried out using light microscopy.Key results – With the initiation of secondary growth, stems lose their circular outline rapidly due to unequal deposition of secondary xylem and formation of successive cambia. New successive cambia initiate from parenchymatous cells as small crescent-shaped fragments on asymmetric/opposite sides and result in a different stem conformation. Though several segments of successive cambia are formed, very few stem samples form complete cambium rings. The secondary xylem formed by successive cambia is diffuse porous with indistinct growth rings and is composed of both wide and narrow (fibriform) vessels, tracheids, fibres, axial and ray parenchyma cells. The secondary phloem consists of sieve tube elements, companion cells, axial and ray parenchyma cells. In fully grown plants, cambial action (internal cambium) occurrs between the intraxylary phloem and protoxylem and produces secondary xylem and phloem near the pith region.Conclusion – Structural alterations and unequal deposition of conducting elements, occurrence of intraxylary phloem and flattening of the stem are suggested to facilitate rapid growth of the plants by providing required minerals and nutrients. Internal cambium formed at the periphery of the pith is bidirectional and produces secondary xylem externally and intraxylary phloem internally. Continued development of intraxylary phloem from the internal cambium provides an additional path for rapid and safe translocation of photosynthates.

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Traumatic Gum-Resin Cavities in the Stem of Ailanthus Excelsa Roxb.

IAWA Journal ◽

10.1163/22941932-90001043 ◽

1987 ◽

Vol 8 (2) ◽

pp. 167-174 ◽

Cited By ~ 8

Author(s):

A.M. Babu ◽

G.M. Nair ◽

J.J. Shah

Keyword(s):

Epithelial Cells ◽

Secondary Xylem ◽

Ailanthus Excelsa ◽

Parenchyma Cells ◽

Ray Parenchyma ◽

Ray Cells ◽

Cell Layers ◽

Ethephon Treatment ◽

Xylem Elements ◽

Ray Parenchyma Cells

Traumatic gum-resin cavities develop in the secondary xylem of the stem of Ailanthus excelsa Roxb. in response to fungal infection and ethephon treatment. After infection or ethephon treatment, traumatic parenchyma in several cell layers develops instead of normal secondary xylem elements. It consists of unlignified axial and ray parenchyma cells. Vessels and fibres are absent. Gum-resin cavities in one or two tangential rows develop in this tissue by the lysis of its axial parenchyma cells. The cavities are bordered by an epithelium. A few layers of traumatic parenchyma cells adjacent to the epithelial cens become meristematic and appear cambiform. The epithelial cells undergo lysis and they evidently contribute to gum-resin formation. As the lysis of epithelial cens proceeds, the adjacent cambiform cens divide to form additional epithelial cells. The process continues for some time and eventually an the axial cells of the traumatic parenchyma break down forming a tangentially anastomosing network of cavities. The cavities do not traverse the ray cells, and the multiseriate rays remain intact like bridges amidst the ramifying cavities.

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Developmental anatomy of natural root grafts in Ficus globosa

Australian Journal of Botany ◽

10.1071/bt9660269 ◽

1966 ◽

Vol 14 (3) ◽

pp. 269 ◽

Cited By ~ 7

Author(s):

AN Rao

Keyword(s):

Secondary Growth ◽

Vascular Cambium ◽

Initial Contact ◽

Secondary Phloem ◽

Developmental Anatomy ◽

Single Root ◽

Aerial Roots ◽

Parenchyma Cells ◽

Ray Cells ◽

Root Grafts

The series of events, and the anatomical changes connected with them, leading to the fusion of aerial roots in Ficus globosa Blume are described. The initial contact between two aerial roots is estabiished by the formation and fusion of epidermai hairs. Secondary growth increases the size of the roots, and consequently the cortices of the two adjacent roots approach one another and become compressed. The cortical tissues thin out in the central region of the compressed zone, but fuse marginally and remain intact. In both roots the ray cells near the contact area become highly meristematic; by active division they produce many parenchyma cells that extend towards each other and finally merge to establish a continuous parenchymatous zone between the steles of the two roots. The cortical tissues, secondary phloem, and vascular cambium in both roots are interrupted by the formation of this new tissue. Later some of the parenchyma cells below the fused regions of the cortex redifferentiate into vascular cambium and extend laterally, joining the pre-existing, interrupted cambia of the two roots. Thus a continuous ring of vascular cambium is reorganized that gives rise to more secondary xylem and phloem. Cork cambium differentiates in the subepidermal layers to form a thick periderm with a smooth surface, so that the fused roots appear externally as a single root. Certain important points of the present study are discussed with reference to previous work.

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Development of Intra- and Interxylary Secondary Phloem in Coccinia indica (Cucurbitaceae)

IAWA Journal ◽

10.1163/22941932-90000072 ◽

2011 ◽

Vol 32 (4) ◽

pp. 475-491 ◽

Cited By ~ 9

Author(s):

Vidya S. Patil ◽

Carmen R. Marcati ◽

Kishore S. Rajput

Keyword(s):

Vascular Bundle ◽

Secondary Xylem ◽

Secondary Growth ◽

Cambial Activity ◽

Vascular Bundles ◽

Secondary Phloem ◽

Stem Anatomy ◽

Axial Parenchyma ◽

Vessel Elements ◽

Coccinia Indica

Stem anatomy and the development of intraxylary phloem were investigated in six to eight years old Coccinia indica L. (Cucurbitaceae). Secondary growth in the stems was achieved by the normal cambial activity. In the innermost part of the thicker stems, xylem parenchyma and pith cells dedifferentiated into meristematic cells at several points. In some of the wider rays, ray cells dedifferentiate and produce secondary xylem and phloem with different orientations and sometimes a complete bicollateral vascular bundle. The inner cambial segments of the bicollateral vascular bundle (of primary growth) maintained radial arrangement even in the mature stems but in most places the cambia were either inactive or showed very few cell divisions. Concomitant with the obliteration and collapse of inner phloem (of bicollateral vascular bundles), parenchyma cells encircling the phloem became meristematic forming a circular sheath of internal cambia. These internal cambia produce only intraxylary secondary phloem centripetally and do not produce any secondary xylem. In the stem, secondary xylem consisted mainly of axial parenchyma, small strands of thick-walled xylem derivatives, i.e. vessel elements and fibres embedded in parenchymatous ground mass, wide and tall rays along with exceptionally wide vessels characteristic of lianas. In thick stems, the axial parenchyma de-differentiated into meristem, which later re-differentiated into interxylary phloem. Fibre dimorphism and pseudo-vestured pits in the vessels are also reported.

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