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Long Distance Transport of Water

At some earlier stage you might have carried out an experiment where you had placed a twig bearing white flowers in coloured water and had watched it turn colour. On examining the cut  end of the twig after a few hours you had noted the region through which the coloured water moved. That experiment very easily demonstrates that the path of water movement is through the vascular bundles, more specifically, the xylem. Now we have to go further and try and understand the mechanism of movement of water and other substances up a plant.

Vascular System in PlantsVascular System in Plants

Long distance transport of substances within a plant cannot be by diffusion alone. Diffusion is a slow process. It can account for only short distance movement of molecules. For example, the movement of a molecule across a typical plant cell (about 50 µm) takes approximately 2.5 s. At this rate, can you calculate how many years it would take for the movement of molecules over a distance of 1 m within a plant by diffusion alone?

In large and complex organisms, often substances have to be moved across very large distances. Sometimes the sites of production or absorption and sites of storage are too far from each other; diffusion or active transport would not suffice. Special long distance transport systems become necessary so as to move substances across long distances and at a much faster rate. Water and minerals, and food are generally moved by a mass or bulk flow system. Mass flow is the movement of substances in bulk or en masse from one point to another as a result of pressure differences between the two points. It is a characteristic of mass flow that substances, whether in solution or in suspension, are swept along at the same pace, as in a flowing river. This is unlike diffusion where different substances move independently depending on their concentration gradients. Bulk flow can be achieved either through a positive hydrostatic pressure gradient (e.g., a garden hose) or a negative hydrostatic pressure gradient (e.g., suction through a straw).

The bulk movement of substances through the conducting or vascular tissues of plants is called translocation. Do you remember studying cross sections of roots, stems and leaves of higher plants and studying the vascular system? The higher plants have highly specialised vascular tissues – xylem and phloem. Xylem is associated with translocation of mainly water, mineral salts, some organic nitrogen and hormones, from roots to the aerial parts of the plants. The phloem translocates a variety of organic and inorganic solutes, mainly from the leaves to other parts of the plants.

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FAQs on Long Distance Transport of Water - Biology Class 11 - NEET

1. What is long distance transport of water?
Ans. Long distance transport of water refers to the movement of water over large distances, typically through channels such as rivers or pipelines, to supply water to areas that are far away from the source of water. This transportation method allows for the redistribution of water resources to regions with water scarcity or to meet the demands of large populations.
2. How is water transported over long distances?
Ans. Water can be transported over long distances through various methods such as pipelines, aqueducts, canals, and tankers. Pipelines are often used for transporting water overland, while aqueducts are elevated structures that carry water across valleys or other obstacles. Canals are artificial waterways that allow for the transportation of water, and tankers are large ships or vessels that transport water across oceans or large bodies of water.
3. What are the benefits of long distance water transport?
Ans. Long distance water transport offers several benefits. It helps in reducing water scarcity in areas with limited water resources by supplying water from regions with surplus water. Additionally, it enables the provision of clean drinking water to populations in need, supports agricultural irrigation in arid regions, and facilitates industrial water supply. It also helps in managing water resources more efficiently, ensuring a sustainable water supply for both human and environmental needs.
4. What are the challenges of long distance water transport?
Ans. Long distance water transport faces several challenges. One major challenge is the cost involved in building and maintaining the infrastructure required for water transportation, such as pipelines or canals. Another challenge is the potential loss of water through leakage or evaporation during transportation, which can reduce the efficiency of the system. Additionally, environmental concerns regarding the impact on ecosystems and habitats along the transport route need to be addressed. Finally, political and legal issues related to water rights and ownership can also pose challenges in implementing long distance water transport projects.
5. Are there any alternatives to long distance water transport?
Ans. Yes, there are alternatives to long distance water transport. One alternative is the implementation of local water management strategies, such as rainwater harvesting, groundwater recharge, and efficient water use practices. These methods aim to conserve and utilize water resources at a local level, reducing the need for long distance transport. Additionally, desalination of seawater or brackish water can provide a local source of freshwater in coastal regions. However, these alternatives may have limitations in terms of cost, availability, and environmental impact, making long distance water transport necessary in certain situations.
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