Why Is the Cortex Tissue Important for Plants?
The tissue of unspecialized cells in plants is called the cortex, it lies between the epidermis(surface cells) and the vascular or conducting tissues of roots and stems. Whereas, cortical cells may contain stored carbohydrates or other substances like resins, latex, essential oils, and tannins.
In some roots along with herbaceous stems rarely in woody stems, the cortical cells in the innermost layer are differentiated into a cell layer called the endodermis. The Casparian strip or plant structure is found in the endodermis. It has woody cell walls and a corky band found around all the cell walls with the exception of those facing toward the axis and therefore the surface of the base or stem or root.
The endodermis with its Casparian strips may operate in regulating the flow of water between outer issues and therefore the vascular cylinder at the centre of the root. Some flowering plants have a starch sheath (a layer of cells with stored starch) within one inch or two inches of shoot tips which lies in the same position as an endodermis.
Anatomy of a Plant Stem
Given below is the cross section of a flax plant stem:
Pith
Protoxylem
Xylem l
Phloem l
Sclerenchyma (bast fibre)
Cortex
Epidermis
Anatomy of Cortex Plant Tissue
The cortex consists of large thin-walled parenchyma cells of the bottom tissue system while showing little to no structural differentiation. The outer cortical cells often obtained unevenly thickened cell walls, called collenchymas cells. A number of the cortical cells could also contain chloroplasts. The cortex sorts of layers of the cells that constitute cork. It is liable for the transportation of the materials into the central cylinder of the basis through diffusion and is also used for food storage within the sort of starch. The endodermis is the innermost layer of the cortex.
In the case of a lichen, the cortex is the “skin”, or outer layer of thallus tissue that covers the undifferentiated cells of the medulla. In Fruticose lichens one cortex encircles the branches, it may be either flattened or have leaf-like forms; foliose lichens have different upper and lower cortices; crustose, placodioid, and squamulose lichens have upper cortex but lacks the lower cortex; while leprose lichens are devoid of the cortex.
Pith
Pith, or medulla, is that tissue in the stems of the vascular plants. Pith consists of spongy and soft parenchyma cells, which store as well as transport nutrients throughout the plant. Pith is found within the centre of the stem in eudicotyledons. In monocotyledons, it also extends into flowering stems and therefore the roots. The pith is encircled by a ring of xylem; the xylem is encircled by a ring of phloem.
What is Phloem?
The living tissue in vascular plants called phloem transports the soluble organic compounds which are manufactured during photosynthesis. Specifically the sugar sucrose, to different parts of the plant where it is needed. This transport process is noted as translocation. The phloem is derived from the Greek word floiós which means "bark" inside the tree, as the name suggests it is the innermost layer. Carl Nageli was the one who coined the term in 1858.
Phloem and Companion Cells
Xylem
Phloem
Cambium
Pith
Companion cells
There are Two Sorts of Companion Cells:
Ordinary companion cells are those which have smooth walls and few or no plasmodesmatal connections to the cells aside from the sieve tube.
Transfer cells are those which have much-folded walls that are adjacent to non-sieve cells, allowing larger areas of transfer. Transfer cells specialized in scavenging the solutes from those during which the cell walls that are actively pumped require energy.
Is Cortex a Primary Tissue?
The mass of primary tissue in stems as well as roots extends inward from the epidermis to the phloem. The cortex may be composed of only one or a mixture of all the three major tissues: collenchymas, parenchyma along with sclerenchyma.
The cortex makes up a substantial proportion of the quantity within the root, particularly within the young roots, where it operates within the transport of water and therefore the ions from the epidermis to xylem and phloem or vascular tissues. In the older roots, it operates primarily as a storage tissue.
Is Cortex a Ground Tissue?
The cortex rests between the hypodermis and ground tissue, together with several layers of parenchyma cells. The bottom tissue is additionally composed of the parenchyma cells and therefore the vascular system.
Cortex and Pith
The cortex is found to the surface and/or round the vascular bundles, while the pith is found within the centre of the stem. Parenchyma cells are the main components of both the cortex and pith. Unlike dicots, monocots usually don’t have an outlined cortex and pith.
Functions of Cortex and Pith
In most plants, Pith and Cortex cells operate to support.
FAQs on Cortex Plant Tissue: Definition, Anatomy & Functions
1. What is the cortex in a plant?
The cortex is a significant region of ground tissue found in the stems and roots of plants. It is located between the outermost layer, the epidermis, and the central vascular cylinder, known as the stele. It plays a crucial role in transport, storage, and providing structural support to the plant.
2. What types of tissues typically make up the plant cortex?
The cortex is primarily composed of large, thin-walled parenchyma cells. However, depending on the plant, it may also contain other tissues. The outermost layer of the cortex, called the hypodermis, can be made of collenchyma in young dicot stems for flexible support, or sclerenchyma in monocot stems for rigid support.
3. What are the main functions of the cortex in plant stems and roots?
The cortex performs several vital functions for the plant, including:
- Storage: The parenchyma cells in the cortex are major sites for storing food, such as starch, as well as water and other substances.
- Transport: It facilitates the movement of water and minerals from the root hairs to the central vascular tissues (xylem).
- Support: Tissues like collenchyma and sclerenchyma within the cortex provide mechanical strength and flexibility to the stem.
- Aeration: The intercellular spaces between cortical cells allow for the exchange of gases.
4. Where exactly is the cortex located within a plant stem?
In a transverse section of a plant stem or root, the cortex occupies the region just beneath the epidermis. It extends inwards to the endodermis, which is considered the innermost layer of the cortex. The endodermis then surrounds the central core of vascular tissue called the stele (containing xylem and phloem).
5. How does the cortex in a monocot stem differ from the cortex in a dicot stem?
In a dicot stem, the cortex is a distinct, well-defined region between the epidermis and the stele. In contrast, a monocot stem typically lacks a well-differentiated cortex and pith. The ground tissue is not separated into these distinct zones, and the vascular bundles are found scattered throughout the ground tissue.
6. Why is the cortex essential for the transport of water and minerals in a root?
The cortex acts as a crucial pathway for water and minerals absorbed by the root hairs. Water must travel across the cortical cells to reach the xylem in the centre. This movement occurs through two main routes: the apoplast pathway (through cell walls and intercellular spaces) and the symplast pathway (through the cytoplasm of connected cells). The cortex facilitates this radial transport until it reaches the endodermis, which then regulates entry into the vascular cylinder.
7. Does the cortex carry out photosynthesis?
In most plants, especially in roots and woody stems, the cortex does not perform photosynthesis as it lacks chloroplasts and is not exposed to light. However, in young, green stems, the outer cortical cells (chlorenchyma) may contain chloroplasts and can perform photosynthesis to a limited extent.
8. What is the significance of having air spaces (intercellular spaces) within the cortical cells?
The presence of intercellular spaces within the cortex is functionally very important. These spaces form a continuous network that allows for the diffusion of gases like oxygen and carbon dioxide. This process, known as aeration, is vital for the respiration of the living cells within the root and stem tissues, especially those located far from the plant's surface.
9. What is the difference between the primary cortex and the secondary cortex?
The primary cortex develops from the primary meristem (apical meristem) during the initial growth of the plant. The secondary cortex, also known as phelloderm, is formed during secondary growth in dicot stems and roots. It is produced inwardly by a secondary meristem called the cork cambium (phellogen) and is part of the periderm, which replaces the epidermis in older plants.
10. How does the structure of the endodermis, the innermost layer of the cortex, relate to its function?
The endodermis is a specialised layer that acts as a gatekeeper. Its cells are characterised by the presence of the Casparian strip, a waterproof band of suberin. This strip blocks the apoplastic pathway, forcing water and dissolved minerals to pass through the cell membrane and cytoplasm of the endodermal cells. This selective process allows the plant to actively control which substances enter the vascular system (xylem), preventing the entry of harmful materials.
