Problem 102 - Objective Biology for NEET

Question

In \(\mathrm{C}_{4}\) plants, the mesophyll cells are connected with bundle sheath cells with the help of (a) Cytoplasmic connection (b) Special connecting tissues (c) Plasmodesmata (d) Connection is not essential

Step-by-Step Solution

Answer

The mesophyll cells in C4 plants are connected with bundle sheath cells through plasmodesmata.

Step 1: Understand the Question

The task is to find out how mesophyll cells are connected with bundle sheath cells in plants of the C4 type. It might be beneficial to review how cells in these types of plants typically connect.

Step 2: Recall Plant Cell Connections

In C4 plants, the mesophyll cells (specialized plant cells where photosynthesis often happens) are in contact with bundle sheath cells (cells surrounding the veins of the plant). This connection allows for the efficient functioning of the C4 photosynthetic pathway.

Step 3: Match with Given Options

Now, match this understanding with the given options. Plasmodesmata are microscopic channels traversing the cell walls of plant cells enabling transport and communication between them, which fits the functional need of connectivity between mesophyll cells and bundle sheath cells in C4 plants.

Key Concepts

Mesophyll Cells

Mesophyll cells are specialized plant cells responsible for photosynthesis. These cells are located in the leaves, sandwiched between the upper and lower epidermis. The primary role of mesophyll cells is to convert sunlight into chemical energy through photosynthesis.
Mesophyll cells are part of the C4 photosynthetic pathway, which is efficient in carbon fixation even under conditions of high temperature and low carbon dioxide.

• Presence in Leaves: Mesophyll cells are found specifically in the inner tissue of leaves, enhancing surface area for light absorption.
• Photosynthesis Specialists: They contain numerous chloroplasts, the organelles where photosynthesis occurs, maximizing energy production.
• Role in C4 Photosynthesis: In C4 plants, these cells capture carbon dioxide and fix it into a four-carbon compound, aiding the bundle sheath cells in efficiently utilizing this fixed carbon.

Understanding mesophyll cells is key to grasping how plants adapt to environmental challenges while maintaining photosynthetic efficiency.

Bundle Sheath Cells

Bundle sheath cells are another crucial component of the C4 photosynthetic pathway. They form a layer surrounding the plant veins, which is essential for the efficient operation of C4 photosynthesis. These cells are tightly linked with mesophyll cells for optimized function.
In C4 plants, the Calvin cycle, a process of photosynthesis, occurs primarily in the bundle sheath cells. This localization helps the plant minimize photorespiration.

• Structural Role: Bundle sheath cells form concentric layers around the veins of a leaf. This structure facilitates efficient nutrient and water transport.
• Photosynthetic Role: These cells contain chloroplasts where the Calvin cycle converts the four-carbon compounds produced by mesophyll cells into glucose.
• Reduced Photorespiration: By tightly packing carbon cycle processes to specific cells, the plant reduces the energy loss from photorespiration, leading to higher efficiency.

The collaboration between mesophyll and bundle sheath cells is a signature adaptation seen in plants like maize and sugarcane, enabling them to thrive in hot, dry environments.

Plasmodesmata

Plasmodesmata are microscopic channels that traverse the cell walls of plant cells, enabling direct communication and transport of materials between cells. They play a crucial role in the connectivity between mesophyll and bundle sheath cells, particularly in C4 plants.
These intercellular channels allow for the passage of ions, molecules, and even genetic material, aiding in maintaining homeostasis within tissues.

• Intercellular Bridges: Plasmodesmata create cytoplasmic bridges between cells, facilitating movement of substances without crossing the cell membrane barrier.
• Transport Efficiency: They ensure that the compounds fixed in mesophyll cells can be efficiently transported to bundle sheath cells where the Calvin cycle proceeds.
• Communication: Chemical signaling through plasmodesmata is vital for coordinating activities between cells, ensuring the optimal functioning of photosynthesis.

In summary, plasmodesmata are fundamental communication pathways that support the remarkable efficiency of the C4 photosynthetic mechanism.