Question

Assertion: Transport of sucrose from leaf to root is called translocation. Reason: This is long distance transport through vascular system of plant.

Short answer

The assertion and reason are both correct, and the reason is the correct explanation for the assertion.

Step-by-step solution

Understanding Terminologies

Firstly, it's crucial to comprehend the terms mentioned. \(Translocation\) refers to the movement of materials from leaves to other tissues throughout the plant. The \(vascular system\) in plants is a complex network of \textit{xylem} and \textit{phloem} that facilitates the movement of water, nutrients, and photosynthates (like sucrose).

Evaluating the Assertion

The assertion states that 'transport of sucrose from leaf to root is called translocation'. We already understood that translocation, indeed, is the term for the movement of materials from leaves to other tissues throughout the plant. Therefore, this assertion is correct.

Evaluating the Reason

The reason provided is 'This is long distance transport through the vascular system of the plant'. This statement is also correct. The vascular system, with its xylem and phloem vessels, are responsible for long distance transport of water, nutrients, and photosynthates within the plant. The sucrose produced in leaves moves towards lower concentration areas, which can be far off parts of the plant, like roots.

Validation of Reason for Assertion

Finally, we assess if the reason does, in fact, justify the assertion. The sucrose produced in the leaves needs to be transported to the roots, which is a long distance, and is facilitated by the vascular system of the plant, thus validating the process as translocation. Hence, the assertion and reason are not just individual truths, but the reason suitably explains the assertion, making the entire statement correct.

Key concepts

Vascular System of Plants

Plants have a sophisticated transportation network known as the vascular system, which is essential for their survival. Unlike animals, plants cannot move to acquire food or water, so they rely on this system to deliver necessary substances to where they're needed.

The vascular system comprises two main types of tissues: xylem and phloem. Xylem is primarily responsible for the transport of water and minerals from the roots to the rest of the plant. It acts somewhat like pipes, carrying these crucial substances upwards against gravity. The strength of the xylem vessels also helps to support the plant structurally.

On the other hand, phloem is responsible for the movement of photosynthetic products, primarily sucrose, throughout the plant. This process is crucial for delivering energy to growing areas, such as new leaves and roots, and for storing energy in fruits and seeds. The phloem tissue is more than a static system; it is dynamic and capable of moving substances in multiple directions to meet the plant's current needs. Overall, the vascular system is a central aspect of plant biology that facilitates growth, reproduction, and resilience.

Sucrose Transport in Plants

The transport of sucrose in plants is a fundamental aspect of their energy distribution system. Sucrose is created during photosynthesis in the leaves, and from there, it must be distributed to all parts of the plant, including roots, stems, flowers, and fruits.

Sucrose transport occurs in the phloem through a process known as translocation. This involves moving sucrose from a 'source' to a 'sink'. The source is typically the leaf where photosynthesis occurs, and the sinks are the locations where the sucrose is needed for growth or storage. It is transported by a pressure-driven flow mechanism, known as the 'pressure-flow hypothesis', where water flows into the phloem to create turgor pressure that helps push the sucrose along the phloem tubes.

The efficiency of sucrose transport is vital for the plant's health, as it ensures that energy is available where needed for cellular processes, growth, and storage. Disruptions in this process can lead to reduced vitality and growth, showcasing the critical role that sucrose transport plays in plant life.

Xylem and Phloem

Xylem and phloem are the two types of transport tissue in plants, each with distinctive roles in the vascular system. They are bundled together in vascular bundles and are distributed throughout the plant.

Xylem, composed of dead cells arranged in tubular fashion, is tasked with the transport of water and dissolved minerals from the roots up to the rest of the plant. This movement is facilitated by transpirational pull and root pressure. Transpiration from the leaves creates a negative pressure that draws water up through the xylem vessels like a straw.

Meanwhile, phloem, consisting of living cells, is involved in the two-way transport of organic nutrients. The principal nutrient transported by the phloem is sucrose, and its movement is driven by a gradient in osmotic pressure. This complex process is governed by the ability of plant cells to actively load and unload sucrose into the phloem network, thereby maintaining a steady flow to various plant parts.

In conclusion, xylem and phloem work in unison to ensure that water, minerals, and energy reach all parts of the plant efficiently and effectively, this mutual relationship embodies the essential nature of vascular tissues in plant life.