Question

In root (a) Endarch arrangement is present (b) Exarch arrangement is present (c) Protoxylem lies towards the centre (d) Metaxylem lies towards the periphery

Short answer

(b) Exarch arrangement is present, (d) Metaxylem lies towards the periphery

Step-by-step solution

Identify the arrangement of xylem

Firstly, it is necessary to recall or look up the correct arrangement of protoxylem and metaxylem in a root. In a root, the protoxylem is found towards the periphery and the metaxylem is found towards the center. This indicates that an exarch arrangement is typically seen in roots.

Match the correct arrangement with the options

Now it's time to match the correct arrangement with the options provided in the exercise. In the case of a root, as already determined, it is correct to say that it features an exarch arrangement, with the protoxylem towards the center and the metaxylem towards the periphery. In terms of the options provided, option (b) Exarch arrangement is present, and option (d) Metaxylem lies towards the periphery align with the features of a root.

Determine the correct answer

Finish the exercise by selecting the correct options based on your analysis, which are options (b) and (d).

Key concepts

Protoxylem

Protoxylem is an essential component in the vascular system of plants. It is the first type of xylem to develop, and its role is crucial for the transport of water and minerals from the soil to the plant. In roots, the protoxylem is strategically positioned towards the outer parts, closer to the periphery. This arrangement allows for the efficient initial distribution of nutrients as the plant begins to grow.
Protoxylem vessels are typically narrower and less complex in structure compared to metaxylem vessels. They can withstand the rapid elongation during the initial stages of root growth without getting damaged.

• The position towards the periphery in roots makes it part of an exarch xylem arrangement.
• It is designed to handle the mechanical and osmotic stresses during the early phases of root development.

Protoxylem's adaptation to the developmental needs of the plant highlights its importance in root function.

Metaxylem

Metaxylem is a later-developing part of the xylem that appears after protoxylem. As the plant matures, metaxylem cells take over the role of water and nutrient transport. These cells are notably larger and more structured than protoxylem cells, accommodating increased demands as the plant grows.
In root anatomy, metaxylem is typically found towards the center. This central placement is integral to its function in providing more permanent support and effective transport pathways.

• It possesses thicker walls, providing strength and support.
• Its larger size contributes to greater efficiency in water transport.
• The position towards the center in roots corresponds with the exarch arrangement.

By being centrally located, metaxylem supports the overall architecture and function of the root system as it further develops.

Root xylem anatomy

Root xylem anatomy involves a complex arrangement of tissues that play a crucial role in plant sustenance. In roots, the xylem displays an exarch arrangement. This means that protoxylem is situated more externally, while metaxylem is placed internally towards the root's center.
This arrangement is particularly advantageous because it adapts as the plant transitions from early growth to more mature stages.

• The exarch pattern provides efficient water transportation from the soil while supporting the root’s structural integrity.
• By developing a well-differentiated arrangement of protoxylem and metaxylem, roots can better adapt to different environmental conditions.

The organization of xylem in roots reflects the evolutionary adaptation to maximize efficiency in both growth and resource distribution, ensuring plant health and development.