Transportation in Plants is a vital process that allows for the movement of essential nutrients, water and other substances throughout the organism. Unlike animals, Plants do not possess a circulatory system. Plants have specialised tissues that serve the same purpose called the Xylem and Phloem.

Plants require a transport system because they are multicellular organisms with various parts that require different substances for their growth and survival. For example, the roots of a Plant need water and minerals, while the leaves require carbon dioxide and sunlight to perform Photosynthesis. These substances cannot be evenly distributed throughout the Plant by diffusion alone, so a specialised transport system is required to ensure that they reach their intended destinations.

In this article, we will discuss the components of the Plant transport system- The Xylem and Phloem, how they work together to transport water, minerals and food throughout the Plant. We will also learn the processes of Transpiration and translocation which is an important section of Plant transport.

Transportation in Plants

• The Transportation system in Plants is a complex network of tissues and structures that allow Plants to move water, nutrients and other important substances throughout their bodies. Although less elaborate than in animals, this system is essential for the survival and growth of Plants.
• Unlike animals, Plant cells do not require material as quickly, as they are less active. 
• Plants are capable of producing their own food through a process known as Photosynthesis. During Photosynthesis, Plants use energy from sunlight to convert carbon dioxide and water into glucose that  is used as an energy source and for growth and maintenance.
• Plants also require oxygen for respiration. Respiration is the process by which they break down glucose to release energy. The branching structure of Plants helps them obtain oxygen by allowing air to reach all parts of the Plant.
• While Plants can produce their own food, they require other necessary materials like nitrogen, phosphorus and other minerals that  are obtained directly from the soil. Plant roots absorb these nutrients from the soil.they  are then transported throughout the Plant by the Transportation system.

Also Check – Transportation in Animals

Components of the Transport System in Highly Organised Plants

Plants require a transport system to move water, nutrients and other essential materials throughout their bodies. The transport system in Plants is composed of two main conducting tissues- 

• Xylem 
• Phloem

Xylem is responsible for the transport of water and minerals obtained from the soil. It is composed of specialised cells called tracheids and vessel elements. It forms a continuous system of water-conducting channels that reach all parts of the Plant. These cells have thick walls made of a complex carbohydrate called lignin that provides strength and support to the Plant.

Phloem, on the other hand, is responsible for the transport of photosynthesis products of Photosynthesis from leaves to other parts of the Plant. It is composed of specialised cells called sieve elements that are connected end-to-end to form sieve tubes. These cells have perforated walls that allow for the movement of materials between cells.

Both Xylem and Phloem tissues carry substances from one part of the Plant body to another. The transport materials in a Plant can be divided into two categories-

• Water and minerals
• Food and other Substances.

Also Check – What are the Components of Transport System in Highly Organised Plants

Xylem 

• Water and minerals are transported through the Xylem tissue. 
• The movement of water and minerals in Plants is achieved by two mechanisms- Root Pressure and Transpiration. 
• Root pressure is created when cells in contact with the soil actively take up ions, creating a difference in the concentration of these ions between the roots and soil. 
• The water that enters into roots from soil eliminates this difference, making the concentrations equal. Hence, there is a steady movement of water into root Xylem from the soil that creates a column of water pushing it upwards. 
• Transpiration is the loss of water in the form of vapours from the aerial parts of the Plant. It takes place mainly through stomata. The water which is lost through the stomata is replaced by water from the Xylem vessels in the leaf. 
• Evaporation of water molecules from the leaf’s cells creates a suction (Transpiration Pull) that pulls water from the Xylem cells of the root.

Also Check – What is Root Pressure

Phloem 

• Food and other Substances are transported through the Phloem tissue. 
• The transport of soluble products (such as sugar) of Photosynthesis from leaves to other parts of the Plant is termed as translocation. 
• Besides the products of Photosynthesis, Phloem also transports amino acids and other substances (such as Plant hormones). 
• These substances are especially delivered to storage organs of roots, fruits, seeds and growing organs. 
• Translocation of substances takes place in the sieve-tubes with the help of adjacent companion cells, both in upward and downward directions. 
• The translocation in Phloem is mainly achieved by utilising energy. Material like sucrose is transferred into the Phloem tissue using energy from ATP that increases the osmotic pressure of the tissue causing water to move into it. 
• The pressure then moves the material in the Phloem to tissues with less pressure. This allows the Phloem to move material according to the Plant’s needs. For example, in the spring, sugar stored in roots or stem tissues would be transported to the buds which need more energy to grow.

Also check – Transportation in Human Beings

Transport of Water and Minerals in Plants – Detailed Explanation

Plants require a constant supply of water and minerals for their growth and survival. The transport system in Plants is responsible for the movement of water and minerals from the roots to the rest of the Plant. This system is mainly made up of two types of tissues – Xylem and Phloem.

The Interconnected Network of Vessels and Tracheids in Xylem Tissues

• The Xylem tissue is responsible for the transport of water and minerals from the roots to the rest of the Plant. 
• It is made up of interconnected vessels and tracheids that form a continuous system of water conducting channels throughout the Plant body. 
• The Xylem vessels are formed from elongated dead cells that are arranged end to end to form long tubes. 
• These cells have thickened walls and are hollowed out to allow water to flow through them easily. 
• The tracheids are similar to vessels but are narrower and have tapered ends.

The Continuous System of Water Conducting Channels

• The Interconnected network of vessels and tracheids in the Xylem tissue forms a continuous system of water conducting channels. 
• This allows for the efficient transport of water and minerals from the roots to the rest of the Plant. 
• The movement of water through the Xylem is driven by the difference in water potential between the soil and the atmosphere. 
• This difference in water potential causes water to move from areas of high concentration to areas of low concentration.

Root Pressure Helps Move Water and Minerals into Root Xylem

• The difference in ion concentration between the roots and the soil, known as root pressure, helps move water and minerals into root Xylem. 
• This occurs when the concentration of solutes in the root cells is higher than the concentration of solutes in the soil. 
• This creates a pressure gradient that causes water to move into the root cells which then pushes water and minerals into the Xylem.

Transpiration Helps Move Water Upwards in Xylem

• Transpiration is the loss of water from stomata that are tiny pores on the surface of leaves. 
• This process creates a negative pressure gradient that pulls water and minerals from the roots upwards through the Xylem. This is known as the Transpiration Pull. 
• The cohesion-tension theory explains how water is transported through the Xylem. 
• It states that water molecules in the Xylem are held together by hydrogen bonds, creating a continuous stream of water that moves from the roots to the rest of the Plant. 
• This process of water transport is very efficient and water can move up the Plant stem to great heights, such as in tall trees.

Also Check – Stomatal control of photosynthesis and transpiration

Transpiration

Transpiration is the process by which water is lost from the aerial parts of Plants in the form of vapour. It mainly takes place through small openings called stomata, that are present on the leaves, stems and other aerial parts of the Plant. The rate of Transpiration is affected by several factors such as temperature, humidity, wind speed and the number and size of stomata.

• Water lost through stomata during Transpiration is replaced by water from Xylem vessels in the leaf. 
• This water is transported from the root to the leaf through a continuous system of interconnected vessels and tracheids in the Xylem tissue. 
• The Xylem vessels are responsible for the transport of water and minerals from roots to aerial parts of the Plant.
• The evaporation of water molecules from the cells of the leaf creates a suction force (Transpiration Pull) that pulls water from the Xylem vessels in the root. 
• This pull is created due to the difference in water potential between the leaf and the root. Water molecules move from an area of high water potential (root) to an area of low water potential (leaf) through a process called osmosis.
• The process of Transpiration is important for the survival of Plants as it helps to transport water and minerals from the soil to the aerial parts of the Plant. It also helps in the regulation of temperature and the uptake of carbon dioxide for Photosynthesis.

Also Check – Why is Transpiration Important for Plants ?

Advantages of Transpiration

1. Absorption and upward movement of water and minerals– Transpiration provides the driving force for the upward movement of water and minerals in the Xylem vessels of Plants. As water evaporates from the leaves, a negative pressure or tension is created. It pulls water and dissolved minerals from the roots up through the stem and into the leaves.
2. Regulation of temperature– Transpiration helps to regulate the temperature of the Plant by cooling the leaves. When water evaporates from the leaf surface, it takes away heat energy that reduces the temperature of the leaf. This is especially important in hot and dry conditions.
3. Constant supply of ions to leaves– Transpiration ensures a constant supply of ions to the leaves. As water moves up through the Plant, it carries dissolved minerals with it. This enables the leaves to have a continuous supply of nutrients.
4. Removal of excess water from the Plant– Transpiration also helps to remove excess water from the Plant. This is important because too much water can be harmful to the Plant, especially in waterlogged soils. By removing excess water, Transpiration helps to maintain the balance of water in the Plant.
5. Facilitation of Photosynthesis– Transpiration also facilitates Photosynthesis, which  is the process by which Plants produce their own food using sunlight, carbon dioxide and water. Without Transpiration, there would not be a continuous supply of water to the leaves that would limit the Plant’s ability to carry out Photosynthesis.

Also Check – 10 Important Factors that Affect the Rate of Transpiration

Transport of Food and Other Substances

• Translocation is the movement of soluble products of Photosynthesis (such as sugar) from leaves to other parts of the Plant. 
• This process is essential for the growth and development of the Plant. Phloem is the vascular tissue responsible for translocation. 
• Unlike Xylem, which moves water and minerals in one direction, Phloem moves substances both up and down the Plant.
• Phloem transports not only sugar but also amino acids and other substances such as Plant hormones. These substances are delivered to storage organs of roots, fruits, seeds and growing organs. The transport of these substances in Phloem is vital for the growth, reproduction and survival of the Plant.
• Translocation takes place in sieve-tubes with the help of adjacent companion cells. Companion cells are specialised parenchyma cells that provide energy and other substances to sieve-tube members, which lack nuclei and other organelles necessary for metabolic functions. 
• These companion cells are linked to sieve-tube members through plasmodesmata that allow the transfer of nutrients and other substances.
• Material like sucrose is transferred into Phloem tissue using energy from ATP, which increases the osmotic pressure of the tissue, causing water to move into it. The increase in pressure then moves the material in the Phloem to tissues with less pressure, allowing Phloem to move material according to the Plant’s needs.
• This process is called pressure flow or mass flow. It allows the Phloem to move the products of Photosynthesis from the source (leaves) to the sink (other parts of the Plant).

Frequently Asked Questions on Transportation in Plants

Why do Plants require a transport system?

Answer- Plants require a transport system because they are multicellular organisms with various parts that require different substances for their growth and survival. These substances cannot be evenly distributed throughout the Plant by diffusion alone, so a specialised transport system is required to ensure that they reach their intended destinations.

What are the specialised tissues in Plants that serve the purpose of a circulatory system?

Answer- The specialised tissues in Plants that serve the purpose of a circulatory system are the Xylem and Phloem.

Also Check – How is Food Transported in Plants

What is the function of Xylem tissue in Plants?

Answer- The Xylem tissue in Plants is responsible for the transport of water and minerals obtained from the soil. It is composed of specialised cells called tracheids and vessel elements, which form a continuous system of water-conducting channels that reach all parts of the Plant.

What is the function of Phloem tissue in Plants?

Answer- The Phloem tissue in Plants is responsible for the transport of products of Photosynthesis from leaves to other parts of the Plant. It is composed of specialised cells called sieve elements, which are connected end-to-end to form sieve tubes.

Also Check – How are Water and Minerals Transported in Plants ?

How does water and mineral transport occur in Plants?

Answer- Water and mineral transport in Plants occurs through the Xylem tissue. The movement of water and minerals in Plants is achieved by two mechanisms- root pressure and Transpiration.

What is root pressure?

Answer- Root pressure is created when cells in contact with the soil actively take up ions, creating a difference in the concentration of these ions between the roots and soil. The water that enters into roots from soil eliminates this difference, making the concentrations equal. Hence, there is a steady movement of water into root Xylem from the soil that creates a column of water pushing it upwards.

What is Transpiration?

Answer- Transpiration is the loss of water in the form of vapours from the aerial parts of the Plant. It takes place mainly through stomata. The water which is lost through the stomata is replaced by water from the Xylem vessels in the leaf.

What is translocation?

Answer- Translocation is the transport of soluble products (such as sugar) of Photosynthesis from leaves to other parts of the Plant through the Phloem tissue. Readmore…

What other substances besides the products of Photosynthesis are transported through the Phloem tissue?

Answer- Besides the products of Photosynthesis, Phloem also transports amino acids and other substances (such as Plant hormones).

How is translocation achieved in the Phloem tissue?

Answer- Translocation in the Phloem tissue is mainly achieved by utilising energy. Material like sucrose is transferred into the Phloem tissue using energy from ATP, which increases the osmotic pressure of the tissue causing water to move into it. The pressure then moves the material in the Phloem to tissues with less pressure.

Also Check – What are the Differences between the Transport of Materials in Xylem and Phloem?

What is the main function of the Xylem tissue in Plants?

Answer- The Xylem tissue is responsible for the transport of water and minerals from the roots to the rest of the Plant.

How does the interconnected network of vessels and tracheids in the Xylem tissue help in the efficient transport of water and minerals in Plants?

Answer- The interconnected network of vessels and tracheids in the Xylem tissue forms a continuous system of water conducting channels, which allows for the efficient transport of water and minerals from the roots to the rest of the Plant.

What is root pressure and how does it help move water and minerals into the root Xylem?

Answer- Root pressure is the difference in ion concentration between the roots and the soil, which creates a pressure gradient that causes water to move into the root cells, which then pushes water and minerals into the Xylem.

What is Transpiration and how does it help move water upwards in the Xylem?

Answer- Transpiration is the loss of water from stomata, which are tiny pores on the surface of leaves. This process creates a negative pressure gradient that pulls water and minerals from the roots upwards through the Xylem. This is known as the Transpiration Pull.

What is the cohesion-tension theory and how does it explain the transport of water through the Xylem?

Answer- The cohesion-tension theory explains how water is transported through the Xylem. It states that water molecules in the Xylem are held together by hydrogen bonds, creating a continuous stream of water that moves from the roots to the rest of the Plant.

What are the advantages of Transpiration for Plants?

Answer- Transpiration provides the driving force for the upward movement of water and minerals in the Xylem vessels of Plants, helps to regulate the temperature of the Plant, ensures a constant supply of ions to the leaves, removes excess water from the Plant and facilitates Photosynthesis.