Xylem Parenchyma

“Xylem parenchyma is an element of complex tissue called “Xylem”. Parenchyma cells of xylem are mainly involved in the storage of carbohydrate, fats and water conduction.”

Table of Contents

• Plant Tissues
  • Meristematic tissues
  • Permanent tissues
• Xylem
  • Structure
  • Diagram
  • Characteristics
  • Functions

Plant tissues can be categorised based on their structure and functions performed.

Plant tissues are classified into two types:

Cells which perform cell division and are responsible for the growth of the plants. There are of 3 types of meristematic tissues based on the regions they are present in plants:

• Apical meristems: It is a primary meristem that is present at the tip of root and shoot. It is responsible for an increase in the length of plants
• Intercalary meristems: Primary meristem which is present between mature tissues
• Lateral meristems: Secondary meristem, which grows later than primary meristem and helps plants grow laterally and produce secondary tissues

They are differentiated cells, which are specialised to carry out a specific function. They generally don’t divide further and attain definite form and size. Permanent tissues are of two types:

• Simple tissues: have only one type of cells (homogeneous), which have a similar structure and function
  • Parenchyma: It is a living tissue. Cells have a thin wall of cellulose. They perform functions like photosynthesis, secretion and storage
  • Collenchyma: Present below the epidermis in dicot stem. Cells are thick at the corner due to cellulose and pectin deposition. They provide mechanical support to the plants at the time of growth
  • Sclerenchyma: Long, narrow dead cells having thick walls of lignin. They provide mechanical support to organs
• Complex tissues: Heterogeneous, have many types of cells. Phloem and Xylem constitute the complex tissue in plants
  • Phloem: Phloem consists of companion cells, phloem parenchyma, sieve tube elements and phloem parenchyma. Phloem transports food from leaves to various parts of the plant
  • Xylem: Xylem consists of tracheids, xylem fibres, vessels and xylem parenchyma. It conducts water to various parts of the plant from roots

Xylem originates from the Greek word “xylon” that means wood. Carl Nägeli coined the word xylem. Xylem is a type of vascular tissue present in plants, which primarily transports water and nutrients from roots to stem and leaves. They also provide mechanical strength to the plants.

On the basis of origin, there are two types of xylem cells:

• Primary xylem: originating from procambium, further divided into protoxylem and metaxylem
• Secondary xylem: originating from the vascular cambium

Xylem is composed of four different kinds of elements:

• Tracheids: Dead, tube-like cells with a tapering end. They are present mostly in gymnosperm and lower angiosperm. They have a thick lignified wall and lack protoplasm. Their main function is water and mineral transportation.
• Vessels: They are present in angiosperms. These are a long cylindrical structure having tube-like appearance. The walls are lignified and have a large central cavity. They are also dead and lack protoplasm. They have many cells called vessel members which are interconnected through a perforation in common walls. Mostly involved in the conduction of water, minerals and give mechanical strength to the plant.
• Xylem Fibre: Dead cell with lignified walls and a central lumen. Involved in water transportation and providing mechanical support.
• Xylem Parenchyma: Only living cells of xylem and store starch and fat. They assist in the short distance transportation of water.

Parenchyma cells associated with xylem are called “xylem parenchyma”.

There are two major types of parenchyma cells in secondary xylem

• Axial parenchyma cells arranged around the axis
• Radial parenchyma cells arranged like a ray, radiating out of the common centre