Tunica-Corpus model of the apical meristem. The epidermal (L1) and subepidermal (L2) layers form the outer layers called the tunica. The inner L3 layer is called the corpus. Cells in the L1 and L2 layers divide in a sideways fashion which keeps these layers distinct, while the L3 layer divides in a more random fashion.

A meristem is a tissue in all plants consisting of undifferentiated cells (meristematic cells) and found in zones of the plant where growth can take place. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Biological tissue is a collection of interconnected cells that perform a similar function within an organism. ... For other uses, see Plant (disambiguation). ...

Differentiated plant cells generally cannot divide or produce cells of a different type. Therefore, cell division in the meristem is required to provide new cells for expansion and differentiation of tissues and initiation of new organs, providing the basic structure of the plant body. Mitosis divides genetic information during cell division. ...

Meristematic cells are analogous in function to stem cells in animals, are incompletely or not at all differentiated, and are capable of continued cellular division (youthful). Furthermore, the cells are small and protoplasm fills the cell completely. The vacuoles are extremely small. The cytoplasm does not contain differentiated plastids (chloroplasts or chromoplasts), although they are present in rudimentary form (proplastids). Meristematic cells are packed closely together without intercellular cavities. The cell wall is a very thin primary cell wall. Mouse embryonic stem cells with fluorescent marker. ... For other uses, see Animal (disambiguation). ... Embryonic stem cells differentiate into cells in various body organs. ... In biology, protoplasm is the living substance inside the cell. ... Schematic of typical animal cell, showing subcellular components. ... Organelles. ... Plant cells with visible chloroplasts. ... Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. ... Chromoplasts are plastids responsible for pigment synthesis and storage. ... Plastids are major organelles uouououuoououououofound only in plants and algae. ...

Maintenance of the cells requires a balance between two antagonistic processes: organ initiation and stem cell population renewal. Antagonistic Bending and straightening of the arm requires antagonistic muscle movement. ...

Meristematic zones

Apical meristems are the completely undifferentiated (indeterminate) meristems in a plant. These differentiate into three kinds of primary meristems. The primary meristems in turn produce the two secondary meristem types. These secondary meristems are also known as lateral meristems because they are involved in lateral growth.

Meristems located at a bud on a branch or shoot are known as a node. Tissue between nodes is known as the internode. A node is the place on a stem where a lateral meristem develops as either a lateral bud or a secondary shoot, often subtended by a leaf. ...

Apical meristems

The apical meristem, or growing tip, is a completely undifferentiated meristematic tissue found in the buds and growing tips of roots in plants. Its main function is to begin growth of new cells in young seedlings at the tips of roots and shoots (forming buds, among other things). Specifically, an active apical meristem lays down a growing root or shoot behind itself, pushing itself forward. Apical meristems are very small, compared to the cylinder-shaped lateral meristems. Pluripotential hemopoietic stem cells or pluripotential hematopoietic stem cells (PHSCs) are stem cells found in the bone marrow. ... Flower buds have not yet bloomed into a full-size flower. ... For other uses, see Plant (disambiguation). ... For other uses, see Root (disambiguation). ... This article is about the plant section. ... Lateral meristems give rise to the secondary plant body. ...

Apical meristems are composed of several layers. The number of layers varies according to plant type. In general the outermost layer is called the tunica while the innermost layers are the corpus. In monocots, the tunica determine the physical characteristics of the leaf edge and margin. In dicots, layer two of the corpus determine the characteristics of the edge of the leaf. The corpus and tunica play a critical part of the plant physical appearance as all plant cells are formed from the meristems. Apical meristems are found in two locations: the root and the stem. Orders Base Monocots: Acorus Alismatales Asparagales Dioscoreales Liliales Pandanales Family Petrosaviaceae Commelinids: Arecales Commelinales Poales Zingiberales Family Dasypogonaceae Monocotyledons or monocots are a group of flowering plants usually ranked as a class and once called the Monocotyledoneae. ... Orders see text Dicotyledons or dicots are flowering plants whose seed contains two embryonic leaves or cotyledons. ...

Shoot apical meristems

The source of all above-ground organs. Cells at the SAM summit serve as stem cells to the surrounding peripheral region, where they proliferate rapidly and are incorporated into differentiating leaf or flower primordia.

The shoot apical meristem is the site of most of the embryogenesis in flowering plants. Primordia of leaves, sepals, petals, stamens and ovaries are initiated here at the rate of one every time interval, called a plastochron. It is where the first indications that flower development has been evoked are manifested. One of these indications might be the loss of apical dominance and the release of otherwise dormant cells to develop as axillary shoot meristems, in some species in axils of primordia as close as two or three away from the apical dome. The SAM consists of 4 distinct cell groups: -

• Stem Cells
• The immediate daughter cells of the stem cells
• A subjacent organising centre
• Founder cells for organ initiation in surronding regions

The four distinct zones mentioned above are maintained by a complex signalling pathway. The organisation centre expresses WUS proteins which maintains the stem cell identity of the overlying cells. The stem cells signal back with CLAVATA3 (CLV3) which is assumed to be a ligand for the CLV1 receptor kinase. When CLV1 interacts with CLV3 it initiates a signalling pathway that results in the repression of the expression of WUS. This controls the size of the organising centre. Mouse embryonic stem cells with fluorescent marker. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...

Root apical meristems

The root apical meristem (RAM) is covered by the root cap, which protects the apical meristem from the rocks, dirt and pathogens.

Intercalary meristem

The intercalary meristems occur only in monocot (particularly grass) stems at the base of nodes and leaf blades. Intercalary meristems are capable of cell division and allow for rapid growth and regrowth of many monocots. Intercalary meristems at the nodes of bamboo allow for rapid stem elongation, while those at the base of most grass leaf blades allow damaged leaves to rapidly regrow. This leaf regrowth in grasses evolved in response to damage by grazing herbivores, but is more familiar to us in response to lawnmowers. Orders Base Monocots: Acorus Alismatales Asparagales Dioscoreales Liliales Pandanales Family Petrosaviaceae Commelinids: Arecales Commelinales Poales Zingiberales Family Dasypogonaceae Monocotyledons or monocots are a group of flowering plants usually ranked as a class and once called the Monocotyledoneae. ...

Floral meristem

When plants begin the developmental process known as flowering, the shoot apical meristem is transformed into an inflorescence meristem which goes on to produce the floral meristem which produces the familiar sepals, petals, stamens, and carpels of the flower.

Apical dominance

Apical dominance is phenomenon where one meristem prevents or inhibits the growth of other meristems. As a result the plant will have one clearly defined main trunk. For example, in trees the tip of the main trunk bears the dominant meristem. Therefore the tip of the trunk grows fast and is not shadowed by branches. If the dominant meristem is cut of, one or more branch tips will assume dominance. The branch will start growing faster and the new growth will be vertical. Over the years the branch may begin to look more and more like an extension of the main trunk. Often several branches will exhibit this behaviour after the removal of apical meristem, leading to a bushy growth.

The mechanism of apical dominance is based on the plant hormone auxin. It is produced in the apical meristem and transported towards the roots in the cambium. If apical dominance is complete, it prevents any branches from forming as long as apical meristem is active. If the dominance is incomplete, side branches will develop. IAA appears to be the most active Auxin in plant growth. ... The vascular cambium is a lateral meristem: The vascular cambium is the source of both the secondary xylem (inwards) and the secondary phloem (outwards), and hence is located between these tissues in the stem. ...

Primary meristems

Apical meristems may differentiate into three kinds of primary meristem:

• Protoderm - lies around the outside of the stem and develops into the epidermis.
• Procambium - lies just inside of the protoderm and develops into primary xylem and primary phloem. It also produces the vascular cambium, a secondary meristem.
• Ground meristem develops into the pith. It produces the cork cambium, another secondary meristem.

These meristems are responsible for primary growth, or an increase in length or height. The epidermis is the outer multi-layered group of cells covering the leaf and young tissues of a plant. ... In vascular plants, xylem is one of the two types of transport tissue in plants, phloem being the other one. ... In vascular plants, phloem is the living tissue that carries organic nutrients, particularly sucrose, a sugar, to all parts of the plant where needed. ... The vascular cambium is a lateral meristem: The vascular cambium is the source of both the secondary xylem (inwards) and the secondary phloem (outwards), and hence is located between these tissues in the stem. ... The centre dark spot (about 1 mm diameter) in this yew wood is the pith Elderberry shoot cut longitudinally to show the broad, solid pith (rough-textured, white) inside the wood (smooth, yellow-tinged). ... Cork cambium is a tissue found in woody plants as part of the periderm. ...

Secondary meristems

There are two types of secondary meristems, these are also called the lateral meristems because they surround the established stem of a plant and cause it to grow laterally (i.e. larger in diameter).

• Vascular cambium - produces secondary xylem and secondary phloem, this is a process which may continue throughout the life of the plant. This is what gives rise to wood in plants. Such plants are called arborescent. This does not occur in plants which do not go through secondary growth (known as herbaceous plants).
• Cork cambium - gives rise to the bark of a tree.

The vascular cambium is a lateral meristem: The vascular cambium is the source of both the secondary xylem (inwards) and the secondary phloem (outwards), and hence is located between these tissues in the stem. ... For other uses, see Wood (disambiguation). ... Arborescent is a term coined by the French thinkers Deleuze and Guattari to characterize thinking marked by insistence on totalizing principles. ... This article is about the plants used in cooking and medicine. ... Cork cambium is a tissue found in woody plants as part of the periderm. ...

Indeterminate growth of meristems

Though each plant grows according to a certain set of rules, each new root and shoot meristem can go on growing for as long as it is alive; In many plants meristematic growth is potentially indeterminate, making the overall shape of the plant not determinate in advance. This is the primary growth.

Cloning

Under appropriate conditions, each shoot meristem can develop into a complete new plant or clone. Such new plants can be grown from shoot cuttings that contain an apical meristem. Root apical meristems are not readily cloned, however. This cloning is called asexual reproduction or vegetative reproduction and is widely practiced in horticulture to mass-produce plants of a desirable genotype. This process is also known as mericloning. For other uses, see clone. ... Horticulture (Latin: hortus (garden plant) + cultura (culture)) are classically defined as the culture or growing of garden plants. ... This article does not cite any references or sources. ...

References

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Méristème

• Mauseth J.D.
• Neil A. Campbell and Jane B. Reece Biology, 6th edition. Benjamin Cummings.
• Schoof et al. The stem cell population of Arabidopsis shoot meristems is maintained by a regulatory loop between CLAVATA and WUSCHEL genes. Cell 100: 635-644.
• Research on meristems: meristemania.org [1]

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