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Why are Xylem and Phloem called Complex Tissues?

Last Updated : 23 Jul, 2025
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The xylem and phloem are called complex tissues because they consist of different types of cells with specialized functions working together to transport water, nutrients, and sugars throughout the plant. This article will give us a detailed answer to the question "Why are Xylem and Phloem called Complex Tissues?"

Why are Xylem and Phloem Called Complex Tissues?

Xylem and phloem are termed complex tissues due to their complex structure and specialized functions in plants. The xylem primarily transports water and minerals from roots to leaves, while the phloem distributes sugars produced in the leaves to other parts of the plant.

These tissues comprise various cell types such as vessel elements, tracheids, sieve tube elements, and companion cells, each serving specific roles in nutrient and water transport. The coordinated action of these diverse cell types within the xylem and phloem enables efficient movement of fluids and nutrients throughout the plant, supporting its growth and development.

Also Read: Difference Between Tracheids And Vessels

Plant-Tissue-System
Types of Plant Tissue

Merismatic Tissue

This is the simple tissue that can continuous cell division. In this type of tissue, growth occurs in the roots and shoot tips of the plant. Based on the region of meristematic tissue in the plant body, we can group the meristems into three types. They are:

  • Apical Meristems: These meristems are situated at the tips of roots and shoots.
  • Intercalary Meristems: The intercalary meristems are situated at the internodes or the foundation of the leaves.
  • Lateral Meristems: These are available on the lateral side of the stem and foundation of a plant.

Permanent Tissue

These tissues are derived from the merismatic tissues and have lost their capacity to divide. This type of tissue can be found in mature plants. They are classified into two types- Simple and complex tissue

Simple Tissue

This is also called homogeneous tissue which consists of a single type of cells. Simple tissues are of three types which are parenchyma, collenchyma, and sclerenchyma.

  • Parenchyma: These tissues are found in the soft parts of a plant like the roots, stems, and leaves. The cells of this tissue contain huge intercellular spaces between them. Each cell has a vacuole in the middle. The functions of parenchyma tissues are photosynthesis, storage, and assisting the plant with drifting on the water.
  • Collenchyma: Collenchyma contains oval, round, or polygonal cells with thick walls. The thickness of the walls is due to pectin, cellulose, and hemicellulose. They are intended to offer mechanical help to the plant structure in parts like the petiole of the leaf.
  • Sclerenchyma: The cells of this tissue are dead. This type of cell lacks a nucleus and cytoplasm. Their cell walls are thickened by lignin and cellulose. Their principal capability is to give mechanical strength to parts of the mature plant.

Complex Tissue

This type of tissue is also known as heterogeneous tissue which consists of different kinds of cells and these differentiated types of cells are coordinated to perform a function. Complex tissues are of two types which are the xylem and phloem.

Complex-Tissue
Complex Tissue

Xylem - Water-Conducting Tissue

The xylem which carries water is made up of tracheary elements like tracheids and vessels mainly. Primary xylem forms during a plant's early growth from the procambium, while the secondary xylem develops from the vascular cambium later on. It is situated deep within plants and consists of trachea, xylem fibers, tracheids, and xylem parenchyma.

Tracheids and vessels have cylindrical shapes, allowing them to transport water and minerals upwards. Their main job is to move water from roots to stems and leaves, along with nutrients, and provide support to the plant. Xylem tissues are tube-like structures without cross walls and resemble stars. Xylem fibers, smaller in size, are found in the center of vascular bundles and play a role in water replacement lost through transpiration and photosynthesis.

Phloem - Food Conducting Tissue

The phloem which transports food, originates from meristematic cells in the vascular cambium with primary phloem coming from the apical meristem and secondary phloem from the vascular cambium. It's located in the outer layers of plants, consisting of companion cells, phloem parenchyma, phloem fibers, sieve cells, and sieve tubes. Unlike xylem, phloem moves in both directions and carries food from leaves to other plant parts.

It does not offer structural support. Phloem fibers, larger than those in xylem, are positioned outside vascular bundles, present in stems and leaves, which eventually transport and grow in roots, fruits, and seeds. Phloem main function is to transport transport sugars (primarily sucrose) produced during photosynthesis.

Characteristics of Xylem and Phloem

Phloem and xylem are complex tissues that perform the transportation of food and water to the parts of plants. They are vascular tissues of the plant. 

Xylem and Phloem

Characteristics

Xylem

Phloem

StructureTubular shape with no cross walls which allows a continuous column of water and facilitates rapid transport within the xylem vessels. There are two types, protoxylem and metaxylem depending on the pattern of lignin.Elongated, tubular shape with thin-walled sieve tubes. The sieve tubes have pores at each end in the cross walls and microtubules that extend between sieve elements allowing the longitudinal flow of material.
ElementsXylem comprises xylem vessels, fibre and tracheids.Xylem comprises xylem phloem fibres, sieve tubes, sieve cells, phloem parenchyma and companion cells.
ShapeXylem is star-shaped.Phloem is not star-shaped.
LocationIt is located in the centre of the vascular bundle, deep in the plant.It is located on the outer side of the vascular bundle.
MovementMovement is unidirectional.Movement is bidirectional.
FunctionsIt provides mechanical strength and responsible for transporting water and other nutrients to the plants.It does not provide mechanical strength and Phloem is living tissue, responsible for transporting food and other organic materials.
Nature of tissueXylem consists of dead cells (parenchyma is the only living cells present in the xylem). Xylem constitutes the bulk of the plant body.Phloem contains living cells (fibres are the only dead cells in the phloem). It forms a small part of the plant body.

Conclusion - Why are Xylem and Phloem called Complex Tissues?

In conclusion, xylem and phloem are termed complex tissues due to their intricate structure and specialized functions in plants. The xylem primarily transports water and minerals from roots to leaves, while the phloem distributes sugars produced in the leaves to other parts of the plant. These tissues consist of various cell types, such as vessel elements, tracheids, sieve tube elements, and companion cells, each playing specific roles in nutrient and water transport. The coordinated action of these diverse cell types within the xylem and phloem enables efficient movement of fluids and nutrients throughout the plant, supporting its growth and development.

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