June 8, 2023
Mesophyll and Bundle Sheath Cells

Difference Between Mesophyll and Bundle Sheath Cells

Explore the distinct characteristics and functions of mesophyll and bundle sheath cells in plant anatomy. Learn about their roles in photosynthesis and the contrasting features that set them apart. Discover the significance of these cells in maintaining plant health and optimizing carbon fixation.

Introduction

Plants are fascinating organisms that possess intricate cellular structures responsible for various functions. Among these structures, mesophyll cells and bundle sheath cells play crucial roles in the process of photosynthesis. While both cell types are involved in this vital process, they exhibit distinct characteristics and serve unique functions within the leaf anatomy. We will investigate the relationship between mesophyll cells and bundle sheath cells, their characteristics as well as functions they serve in plant health and growth.

Definition of Mesophyll and Bundle Sheath Cells

Mesophyll Cells: Mesophyll cells can be defined as plant cells that reside in mesophyll tissue between epidermal layers; this layer plays an essential part in photosynthesis (a process by which plants convert light energy to chemical energy) by providing vital support cells to photosynthesis processes. Mesophyll cells play an integral part in photosynthesis processes by producing chemical energy from light energy through photosynthesis processes. Mesophyll cells are characterized by their high chloroplast content, which contains the pigment chlorophyll responsible for capturing sunlight. They account for most of the photosynthetic activity within leaves.

Bundle Sheath Cells: Bundle sheath cells are another type of specialized plant cells that surround the vascular bundles in the leaves of C4 and some CAM (Crassulacean Acid Metabolism) plants. These cells lie just underneath and overlying the upper epidermal layer to form an outer protective barrier over the lower epidermis and protect vessels that run beneath their surfaces. Bundle sheath cells play a crucial role in carbon fixation, which is the process of converting inorganic carbon dioxide into organic compounds during photosynthesis. They typically contain low levels of chloroplasts designed for carbon fixation tasks.

Mesophyll cells are primarily involved in photosynthesis, while bundle sheath cells have a specialized role in carbon fixation. They have distinct structural and functional differences, and their arrangement and distribution within leaves vary depending on the plant’s photosynthetic pathway (C3, C4, or CAM). Understanding the characteristics and functions of mesophyll and bundle sheath cells is essential for comprehending the mechanisms of photosynthesis and the adaptations of different plant species to various environmental conditions.

Importance of mesophyll and bundle sheath cells in photosynthesis

Mesophyll and bundle sheath cells play crucial roles in the process of photosynthesis, contributing to the overall efficiency of this vital metabolic process in plants.

Here are the key reasons why these cell types are important in photosynthesis:

Mesophyll Cells:
1. Light Capture: Mesophyll cells contain a high concentration of chloroplasts, which contain the pigment chlorophyll. Chlorophyll absorbs solar light energy to initiate photosynthesis. The abundance of chloroplasts in mesophyll cells maximizes the absorption of light energy, enhancing photosynthetic efficiency.

2. Gas Exchange: Mesophyll cells are responsible for facilitating the exchange of gases involved in photosynthesis. The atmosphere is encased with air and intercellular spaces interlinked together that enable the diffusion of carbon dioxide (CO2) inside cells as well as the emission of oxygen produced during photosynthesis.

3. Carbon Dioxide Fixation: Mesophyll cells play a crucial role in fixing atmospheric carbon dioxide during the initial steps of photosynthesis. Carbon dioxide can be transformed into organic compounds through various biochemical reactions that take place within mesophyll cells such as Calvin Cycle.

Bundle Sheath Cells:
1. Carbon Fixation: Bundle sheath cells are specialized for the process of carbon fixation. These cells are involved in the concentrated and efficient fixation of carbon dioxide. They have unique anatomy and biochemistry that minimize wasteful photorespiration and enhance the efficiency of carbon fixation.

2. Regulation of Carbon Dioxide Concentration: Bundle sheath cells act as a barrier and regulate the concentration of carbon dioxide reaching the chloroplasts. This technique creates an increased concentration of carbon dioxide near an enzyme responsible for fixing carbon, thus lessening oxygen-inhibition effects while simultaneously increasing photosynthesis efficiency.

3. Reduction of Photorespiration: Bundle sheath cells help to reduce the occurrence of photorespiration, a wasteful process that can occur in certain conditions. By spatially separating the processes of carbon fixation and the release of oxygen, bundle sheath cells minimize the interaction between oxygen and the enzyme involved in carbon fixation, reducing the likelihood of photorespiration.

Mesophyll cells are responsible for light capture, gas exchange, and initial carbon dioxide fixation, while bundle sheath cells contribute to efficient carbon fixation, regulation of carbon dioxide concentration, and reduction of photorespiration. The coordinated functioning of these cell types ensures the effective utilization of light energy and the optimization of photosynthetic efficiency in plants.

What are Mesophyll Cells?

Mesophyll cells are specialized plant cells that are primarily found in the mesophyll tissue of leaves. Mesophyll tissues, located between the lower and upper epidermal layers of leaves, account for most photosynthetic activity within plants.

Mesophyll cells are characterized by their high chloroplast content. Chloroplasts are organelles within cells that contain chlorophyll to capture sunlight energy for photosynthesis. Mesophyll cells’ chloroplasts allow them to capture sun rays and convert them to chemical energy via the photosynthesis process.

There are two primary mesophyll cell types, known as palisade mesophyll cells and mesophyll cells with spongey surfaces. Palisade mesophyll cells are elongated and tightly packed, usually located near the upper epidermis of the leaf. They contain numerous chloroplasts and are responsible for the majority of photosynthesis in the leaf.

Spongy mesophyll cells, on the other hand, are more loosely arranged with air spaces between them. They are located beneath the palisade mesophyll cells and also contain chloroplasts. Spongy mesophyll cells facilitate gas exchange within the leaf, allowing for the uptake of carbon dioxide and the release of oxygen during photosynthesis.

Mesophyll cells play an integral part in photosynthetic processes by collecting light energy, housing chloroplasts, and performing biochemical reactions that transform water and carbon dioxide into oxygen and glucose. Their arrangement and structure optimize light absorption and gas exchange, making them essential for efficient photosynthesis in plants.

Mesophyll Cells

Mesophyll cells function

Mesophyll cells perform several important functions in plants, primarily related to the process of photosynthesis.

Here are the key functions of mesophyll cells:

1. Photosynthesis: Mesophyll cells are the primary site of photosynthesis in leaves. They contain a high concentration of chloroplasts, which house the pigment chlorophyll responsible for capturing light energy. Mesophyll cells absorb sunlight, using it to convert carbon dioxide (CO2) and water (H2O) into glucose (C6H12O6) and oxygen (O2). They do so through chemical reactions which transform it all into something useful – oxygen for breathing purposes!

2. Gas Exchange: Mesophyll cells facilitate the exchange of gases involved in photosynthesis. Through tiny openings called stomata, located mainly on the lower surface of leaves, carbon dioxide enters the leaf, and oxygen exits. Carbon dioxide from the atmosphere is taken up and used by mesophyll cells during photosynthesis to produce oxygen for release into the surrounding air as an added by-product of photosynthesis.

3. Water Storage and Regulation: Mesophyll cells also have a role in regulating water balance within the leaf. They contain large central vacuoles that can store water and help maintain turgidity, which is important for cell stability and proper functioning. Mesophyll cells participate in the regulation of stomatal opening and closure, influencing the rate of transpiration and water loss from the leaf.

4. Chloroplast Distribution: Mesophyll cells distribute chloroplasts in a way that optimizes light absorption. In leaves, palisade mesophyll cells are located near the upper epidermis and have a high density of chloroplasts. They receive direct sunlight and are responsible for capturing most of the light energy. Spongy mesophyll cells, located beneath the palisade layer, also contain chloroplasts and facilitate gas exchange while providing structural support to the leaf.

Mesophyll cells are specialized for photosynthesis, gas exchange, and water regulation. Their high chloroplast content, strategic arrangement, and metabolic activities are essential for efficient light capture, carbon dioxide uptake, and glucose production, enabling plants to sustain their energy needs and contribute to the overall functioning of ecosystems.

Spongy mesophyll cells

Spongy mesophyll cells can be found in the mesophyll tissue of leaves. They are located beneath the palisade mesophyll cells and play important roles in photosynthesis and gas exchange.

Here are some key characteristics and functions of spongy mesophyll cells:

1. Structure: Spongy mesophyll cells are characterized by a loose and irregular arrangement. They have abundant intercellular spaces between them, creating a spongy appearance. These air spaces facilitate the diffusion of gases within the leaf.

2. Chloroplast Distribution: Spongy mesophyll cells also contain chloroplasts, although they have a lower chloroplast density compared to palisade mesophyll cells. Chloroplasts in spongy mesophyll cells contribute to photosynthesis by capturing light energy and carrying out the biochemical reactions involved in the synthesis of glucose.

3. Gas Exchange: One of the primary functions of spongy mesophyll cells is to facilitate gas exchange within the leaf. Intercellular spaces enable gas exchange between cells such as oxygen and carbon dioxide. Carbon dioxide enters mesophyll cells spongy through their stomata which are tiny holes on leaf surfaces while photosynthesis generates oxygen that escapes back into the atmosphere through photocatalysis.

4. Adaptation to Water Availability: The structure of spongy mesophyll cells can vary depending on the plant species and environmental conditions. In some plants, such as those adapted to dry environments, spongy mesophyll cells may be more extensive, allowing for increased water storage and contributing to the plant’s ability to withstand water scarcity.

5. Role in Photosynthetic Efficiency: The presence of spongy mesophyll cells enhances the overall efficiency of photosynthesis. The air spaces between these cells promote better diffusion of gases, ensuring an adequate supply of carbon dioxide for photosynthesis. Intercellular spaces allow oxygen surplus to escape more efficiently and decrease the chances of damage to photosynthesis machinery from oxidation reactions.

Spongy mesophyll cells have a loose arrangement, contain chloroplasts, and provide essential functions in gas exchange and photosynthesis. Their presence in the mesophyll tissue allows for efficient diffusion of gases, optimizing the exchange of carbon dioxide and oxygen, and contributing to the overall performance of photosynthesis in plant leaves.

What are Bundle Sheath Cells?

Bundle sheath cells are specialized plant cells that surround the vascular bundles in the leaves of certain plants, specifically C4 and some CAM (Crassulacean Acid Metabolism) plants. These cells are strategically positioned within the leaf and have important roles in carbon fixation and the regulation of carbon dioxide concentration.

Here are the key characteristics and functions of bundle sheath cells:

1. Location and Arrangement: Bundle sheath cells are located adjacent to the vascular bundles, which are composed of xylem and phloem tissues. They form a protective layer around the vascular bundles and are usually found in concentric layers around them. Bundle sheath cells are present in leaves, stems, and other plant organs that contain vascular tissue.

2. Cell Structure: Bundle sheath cells typically have a compact and dense arrangement, with little intercellular space. They have a distinct anatomy compared to other leaf cells, with walls that are thicker and more rigid. Bundle sheath cells may contain chloroplasts, but their chloroplast content is lower compared to mesophyll cells.

3. Carbon Fixation: One of the primary functions of bundle sheath cells is to participate in the process of carbon fixation. These cells are involved in the concentrated and efficient fixation of carbon dioxide. Photosynthesis requires specific enzymes and biochemical pathways that enable the conversion of carbon dioxide to organic substances such as malate or oxaloacetate for photosynthesis to take place.

4. Regulation of Carbon Dioxide Concentration: Bundle sheath cells act as a barrier and regulate the concentration of carbon dioxide reaching the chloroplasts. They help maintain a higher concentration of carbon dioxide close to the enzyme responsible for carbon fixation, reducing the effects of oxygen inhibition and enhancing the efficiency of photosynthesis. This spatial separation of carbon dioxide and oxygen within bundle sheath cells helps minimize the occurrence of photorespiration.

5. Connection with Mesophyll Cells: Bundle sheath cells have a close relationship and functional connection with adjacent mesophyll cells. In C4 plants, mesophyll cells initially fix carbon dioxide into a four-carbon compound, which is then transported to the bundle sheath cells. Within the bundle sheath cells, the four-carbon compound is decarboxylated to release carbon dioxide for the Calvin cycle, while the resulting three-carbon compound is transported back to mesophyll cells. This mechanism allows for efficient carbon fixation and minimizes wasteful photorespiration.

Bundle Sheath Cells

Bundle sheath cells are specialized plant cells that surround the vascular bundles and have important roles in carbon fixation and the regulation of carbon dioxide concentration. Their unique anatomy, biochemistry, and connection with adjacent mesophyll cells contribute to the efficiency of photosynthesis in C4 and some CAM plants.

Bundle sheath cells function

Bundle sheath cells perform several crucial functions in plants, particularly in the context of certain photosynthetic pathways like C4 and CAM.

Here are the main functions of bundle sheath cells:

1. Carbon Fixation: Bundle sheath cells are responsible for the concentrated fixation of carbon dioxide (CO2) into organic compounds during photosynthesis. Mesophyll cells play an integral part in carbon fixation by taking in CO2, then turning it into 4-carbon compounds through photosynthesis. This compound is then transported to the bundle sheath cells, where it is decarboxylated to release CO2, which is then used in the Calvin cycle to produce sugars. Bundle sheath cells contain special enzymes called PEP carboxylase or PEPCK that aid in carbon fixation processes.

2. Concentration and Regulation of CO2: Bundle sheath cells play a vital role in maintaining high concentrations of CO2 near the enzyme responsible for carbon fixation. By acting as a barrier and regulating the movement of gases, bundle sheath cells help to reduce the oxygen (O2) concentration around the enzyme. This separation of CO2 and O2 minimizes the occurrence of wasteful photorespiration and enhances the efficiency of carbon fixation.

3. Metabolic Support: Bundle sheath cells provide metabolic support to the photosynthetic process. They contain specialized organelles, such as mitochondria, that supply ATP and other necessary energy sources for the biochemical reactions involved in carbon fixation and subsequent sugar synthesis. Bundle sheath cells also facilitate the transport of metabolites between mesophyll cells and the vascular tissue.

4. Water Conservation: Such as C4 and some CAM plants, bundle sheath cells help to conserve water by reducing the rate of transpiration. The compact arrangement of bundle sheath cells limits the exposure of the leaf surface to the external environment, thereby reducing water loss through stomatal openings. This adaptation is particularly advantageous in arid or water-limited environments.

5. Storage and Distribution of Products: Bundle sheath cells may serve as sites for the storage and distribution of the organic compounds produced during photosynthesis. In C4 plants, bundle sheath cells accumulate starch or other carbohydrate reserves, which can be subsequently used during periods of high energy demand or under conditions unfavorable for photosynthesis.

Bundle sheath cells have specialized functions related to carbon fixation, concentration regulation, metabolic support, water conservation, and storage/distribution of products. Their strategic placement and unique characteristics are essential for optimizing photosynthetic efficiency, particularly in plants employing C4 or CAM pathways, and contribute to the adaptation and success of these plant species in diverse environmental conditions.

Bundle sheath cells in c3 plants

Bundle sheath cells have a different role compared to their function in C4 and CAM plants. While they are not directly involved in carbon fixation, bundle sheath cells in C3 plants still play important roles in the overall process of photosynthesis.

Here are the main functions of bundle sheath cells in C3 plants:

1. Vascular Connection: Bundle sheath cells in C3 plants are connected to the leaf’s vascular system, specifically the xylem, and phloem. They form a protective layer surrounding the vascular bundles, which contain the xylem vessels responsible for water transport and the phloem tubes responsible for sugar transport. The presence of bundle sheath cells ensures an efficient exchange of water, minerals, and sugars between the leaf and the rest of the plant.

2. Structural Support: Bundle sheath cells provide structural support and maintain the integrity of the leaf tissue. They have thickened cell walls and a compact arrangement, which helps in maintaining the overall shape and stability of the leaf. This structural support is especially important in larger leaves where mechanical strength is required.

3. Storage and Transport: Bundle sheath cells may serve as sites for the storage of various compounds, including sugars, starch, and other metabolites. They can accumulate these reserves and transport them to other parts of the plant as needed. Bundle sheath cells act as a reservoir for storing energy-rich molecules produced during photosynthesis and help distribute them to support growth, development, and metabolic activities in different plant organs.

4. Defense and Protection: Bundle sheath cells contribute to the defense mechanisms of the leaf. Secondary metabolites that these plants create include phenolic compounds or defense-related enzymes which play a part in protecting them against herbivores, pathogens, or environmental stressors. The presence of bundle sheath cells enhances the overall resilience and survival of the leaf.

5. Metabolic Support: While bundle sheath cells in C3 plants are not directly involved in carbon fixation, they provide metabolic support to adjacent mesophyll cells. They help facilitate the transport of metabolites such as amino acids, sugars, and organic acids between mesophyll cells as well as blood vessels. Bundle sheath cells contribute to the efficient distribution of nutrients and metabolic intermediates throughout the leaf.

Bundle sheath cells primarily serve as supportive cells involved in the vascular connection, structural support, storage, defense, and metabolic support. While their roles may differ from C4 and CAM plants, they are integral components of the leaf’s functional organization and contribute to the overall efficiency of photosynthesis and plant growth in C3 species.

Difference between Mesophyll and Bundle Sheath Cells

Mesophyll and Bundle Sheath Cells are two distinct types of cells found in plant leaves, and they have different structures, locations, and functions.

Here are the main differences between mesophyll cells and bundle sheath cells:

1. Structure and Location:
• Mesophyll Cells: Mesophyll cells are located between the upper and lower epidermis of the leaf. They are loosely arranged and contain abundant intercellular spaces, allowing for efficient gas exchange. Mesophyll cells can typically be identified by an abundance of chloroplasts which play an essential part in photosynthesis.

• Bundle Sheath Cells: Bundle sheath cells surround the vascular bundles within the leaf. They are tightly packed and arranged in one or more layers, adjacent to the phloem and xylem. Bundle sheath cells have fewer intercellular spaces and contain fewer chloroplasts compared to mesophyll cells.

2. Chloroplast Distribution:
• Mesophyll Cells: Mesophyll cells have a high density of chloroplasts, particularly in the palisade mesophyll cells located near the upper epidermis. These chloroplasts are responsible for capturing light energy and conducting photosynthesis.

• Bundle Sheath Cells: While bundle sheath cells may contain chloroplasts, their chloroplast content is generally lower compared to mesophyll cells. The chloroplasts in bundle sheath cells are specialized for specific functions related to carbon fixation and other metabolic processes.

3. Photosynthetic Functions:
• Mesophyll Cells: Mesophyll cells are the primary sites of photosynthesis in leaves. These organisms use photosynthesis to take in light, absorb CO2, and convert it to glucose via photosynthesis. Mesophyll cells play a crucial role in capturing light energy and carrying out the biochemical reactions involved in photosynthesis.

• Bundle Sheath Cells: Bundle sheath cells are involved in carbon fixation. They receive the products of CO2 capture from adjacent mesophyll cells and participate in the concentrated fixation of CO2 into organic compounds. Bundle sheath cells serve as sites for specialized biochemical pathways and enzymes that enable efficient carbon fixation and subsequent sugar synthesis.

4. Gas Exchange:
• Mesophyll Cells: Mesophyll cells have abundant intercellular spaces, allowing for the diffusion of gases, such as CO2 and oxygen (O2). Photosynthesis contributes significantly to cleaning up CO2 from the atmosphere while simultaneously producing O2.

• Bundle Sheath Cells: Bundle sheath cells have fewer intercellular spaces compared to mesophyll cells. Their compact arrangement limits the direct exchange of gases with the external environment. However, bundle sheath cells play a role in regulating CO2 concentration within the leaf, maintaining a favorable environment for photosynthesis.

Mesophyll and Bundle Sheath Cells

Mesophyll cells and bundle sheath cells differ in their structure, location, chloroplast distribution, and photosynthetic functions. Mesophyll cells are responsible for the bulk of photosynthesis, while bundle sheath cells have specialized roles in carbon fixation, concentration regulation, and metabolic support in certain plant species and photosynthetic pathways.

Examples of Different Plant Types

Mesophyll cells and bundle sheath cells can be found in various plant types, but their characteristics and functions can vary.

Here are examples of plant types where these cell types are commonly found:

Mesophyll Cells:
1. Dicotyledonous Plants: Mesophyll cells are abundant in the leaves of dicotyledonous plants, which include many familiar flowering plants and trees. Examples include sunflowers and roses as well as oak or maple trees. Mesophyll cells typically can be divided into two components – palisade mesophyll cells located near the upper edge of a leaf’s leaf blade; and mesophyll cells located underneath.

2. Monocotyledonous Plants: Mesophyll cells are also present in the leaves of monocotyledonous plants. Monocots include grasses (such as wheat, rice, and maize), lilies, orchids, and palms. Mesophyll cells tend to have less distinctive palisade layers or spongy layers as seen with dicots, similar to their dicot counterparts.

Bundle Sheath Cells:
1. C4 Plants: Bundle sheath cells with specialized functions are a characteristic feature of C4 plants. C4 plants have adapted to efficiently fix carbon dioxide, minimizing photorespiration. C4 plants include corn (maize), sugarcane sorghum, and various grass species. In these plants, bundle sheath cells surround the vascular bundles and are responsible for the concentrated carbon fixation process.

2. CAM Plants: Some CAM plants also possess bundle sheath cells, although their functions may differ from those in C4 plants. CAM (Crassulacean Acid Metabolism) plants, such as succulents like cacti and certain orchids, have adapted to arid environments by performing carbon fixation at night and storing it as organic acids. Bundle sheath cells in CAM plants are involved in storing and releasing the fixed carbon dioxide during the day when stomata are closed to reduce water loss.

Mesophyll cells can be found across many plants and function similarly, while bundle sheath cells tend to specialize in specific pathways of photosynthetic reactions such as C4 photosynthesis (CAM photosynthesis) which appear more frequently and occur only within specific species of plants.

Conclusion

Understanding the difference between Mesophyll and Bundle Sheath Cells is crucial for comprehending the intricate process of photosynthesis and its significance in plant biology. While mesophyll cells act as the primary site for capturing light energy and initiating photosynthesis, bundle sheath cells play a vital role in carbon fixation and optimizing the efficiency of this process. Cells cooperate to promote overall plant health, growth, and adaptation to different environments.