Saturday, 9 May 2020

Plant structure ( Morphology and Anatomy)

Plant structure ( Morphology and Anatomy)

In this article, we are providing information about plant structure include anatomy and morphology, you can also know cell wall structure and more. The state of the plant is very diverse, not only among its many phyla but also within species. Many of these have become extinct, with distinct distinctions in the body parts of the oldest vascular plants such as roots and leaves.

Figure. Morphological plant structure.

The presence of these organs reflects increased specialization, especially among modern vascular plants in relation to the demands of terrestrial existence. Obtaining water, for example, is a major challenge, and roots are adapted for water absorption from the soil. Leaves, roots, branches, and flowers all vary in size from plant to plant.
The development of the plant structure can be precisely controlled as these parts, but some aspects of leaf, stem, and root development are quite flexible. This article emphasizes the integrated aspects of plant form, using a flowering plant as a model.

Vascular plants have roots and shoots

The avascular plant has a root system and a pellet system. Among their tips are roots and shoots, called apes.
The root system anchors the plant and enters the soil, allowing it to absorb water and ions to nourish the plant. Root systems are often widespread, which can produce great strength to advance growing roots. Roots evolved later than the shoot system as an adaptation to living on land.

Structure of plant cell wall

Figure. Anatomy structure of plant cell wall.

The shoot system consists of leaves and stems. The major sites of photosynthesis serve as a scaffold for the position of the stem leaves, the arrangement, shape, and other characteristics of the leaves are important in the production of plant food. Flowers, other reproductive organs, and ultimately, fruits and seeds are also formed on the shoot.

The repeating unit of the vegetative shoot consists of the internode, node, leaf, and axillary bud, but not reproductive structures. An axillary bud is the latest shoot apex that allows the plant to replace a branch or main shoot if it is eaten by a shepherd. A vegetative axillary bud has the capacity to replace the primary shoot. When the plant is transferred to the reproductive stage of development, these axillary buds can produce flower shoots.

The root and the shoots are made up of three types of tissue

Plant cell types can be distinguished by the size of their vacuoles, whether they are living or not at maturity, and by the thickness of their cellulose cell walls, a distinguishing feature of plant cells. Some cells have only a primary cell wall of cellulose, synthesized by the protoplast near the cell membrane. Microtubules align within the cell and determine the orientation of the cellulose fibers. Cells that support the plant body have more heavily reinforced cell walls with multiple layers of cellulose and other strengthening molecules, including lignin and pectin. Cellulose layers are laid down at angles to adjacent layers like plywood; this enhances the strength of the cell wall.

The sprouts, roots, and leaves all have three types of basic tissue: ground, dermal, and vascular tissue. Because each of these tissues extends through the root and shoot systems, they are called tissue systems. In most plants, the cell layer of the epidermis, and cutaneous tissue is thick, and it forms an outer protective covering for the plant. Ground tissue cells perform storage, photosynthesis functions in addition to supporting plants and making protective fibers. Vascular tissue carries fluids and dissolved substances throughout the body. Each of these issues and their many functions are described in more detail in later sections.

New growth occurs at meristems

When a seed sprout, only a tiny portion of the adult plant exists. Although embryonic cells can undergo division to form many types of cells, most adult cells are more restricted. The development of the plant body is based on the activity of shoots and root apices as well as properties found in other parts of the plant. depends on. Meristem cells are indifferent which can divide indefinitely and give rise to many differentiated cells.

Overview of meristems

Meristems are clusters of small cells with dense cytoplasm and proportionately large nuclei that act as stem cells do in animals. One cell divides to give rise to two cells, one of which remains meristematic, while the other contributes to the body of the plant. In this way, cells of the meristem continuously renew. 

 Meristem cell division

Figure.  Meristem cell division.

Molecular genetic evidence supports the hypothesis that animal stem cells and plant meristem cells may share some of the commonest of gene expression. For example, both plant meristem and animal stem cells share the Retinoblastoma gene, which determines whether a cell continues dividing or differentiates. The expanding cell of both the root and shoot results in repeated divisions and subsequent elongation of the cells produced by the epistemic merge. In woody plants, lateral meristems produce an increase in root and shoot diameter.

Apical meristems

The apical meristem and roots are located at the tips showing in this anatomy structure diagram. The cells of the epistemic meristem divide, during the period of development, and continuously add more cells to the tips. The tissues derived from the apical meristems are called primary tissues, the expansion of the root and stem is known as the primary plant body structure. Some plants have young, soft sprouts and a tree body in the primary plant body. Both the root and shoot apical meristems are made up of fragile cells that need protection. The root apical meristem is protected by the root cap, the anatomy of which is described in section 36.3. Root meristem cells are formed by the root cap, closed and transferred to the root through the soil. In contrast, the leaf primordia give rise to the shoot apical meristem, which is particularly susceptible to desiccation due to exposure to air and sun.

 Apical meristems

Figure. Anatomy structure of Apical meristems.

The apical meristem gives rise to the three tissue systems by first initiating primary meristems. The three primary meristems are the protoderm, which forms the epidermis; the procambium, which produces primary vascular tissues (primary xylem for water transport and primary phloem for nutrient transport); and the ground meristem, which differentiates further into ground tissue. In some plants, such as horsetails and corn, intercalary meristems arise in stem internodes (spaces between leaf attachments), adding to the internode lengths. If you walk through a cornfield on a quiet summer night when the corn is about knee-high, you may hear a soft popping sound. This sound is caused by the rapid growth of the intercalary meristems. The amount of stem elongation that occurs in a very short time is quite surprising.

Lateral meristems

Many herbaceous plants (that is, plants with fleshy, not woody, stems) exhibit only primary growth, but others also exhibit secondary growth, which may result in a substantial increase of diameter. In anatomy structure of Secondary growth is accomplished by the lateral meristems—peripheral cylinders of meristematic tissue within the stems and roots that increase the girth (diameter) of gymnosperms and most angiosperms. Lateral meristems form from ground tissue that is derived from apical meristems. Monocots are the major exception.

Although secondary growth increases girth in many nonwoody plants, its effects are most dramatic in woody plants, which have two lateral meristems. Within the bark of a woody stem is the cork cambium—a lateral meristem that contributes to the outer bark of the tree. Just beneath the bark is the vascular cambium—a lateral meristem that produces secondary vascular tissue. The vascular cambium forms between the xylem and phloem in vascular bundles, adding secondary vascular tissue to both of its sides. Xylem is added to the inside of the vascular cambium, and the phloem is added to the outside.

Apical and lateral meristems.

Figure. Anatomy structure of Apical and lateral meristems.

In this anatomy structure, Secondary xylem is the main component of wood. Secondary phloem is very close to the outer surface of a woody stem. Removing the bark of a tree damages the phloem and may eventually kill the tree. Tissues formed from lateral meristems, which comprise most of the trunk, branches, and older roots of trees and shrubs, are known as secondary tissues and are collectively called the secondary plant body.

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