Transportation in plants and its efficiency are amazing. Trees transport all the nutrients and water it needs for survival from its roots to the tips of the leaves. In the case of transportation in plants, the biggest constraint is water as it ends up being a limiting factor in growth. To overcome this problem, trees and other plants have the perfect system for the absorption and translocation of water. Plants contain a vast network of conduits which consist of xylem and phloem. This is more like the circular system that transports blood throughout the human body. Similar to the circular system in humans, the xylem and phloem tissues extend throughout the plant. These conducting tissues originate from the roots and move up through the trunks of trees. Later they branch off into the branches and then branching even further into every leaf, like spider webs.
Transportation in Plants
The phloem is responsible for translocation of nutrients and sugar like carbohydrates, produced by the leaves to areas of the plant that are metabolically active. The xylem is also composed of elongated cells like the phloem. However, xylem is especially accountable for transporting water to all parts of the plants from the roots. Since they serve such an important function, a single tree would have a lot of xylem tissues.
Transpiration is the driving force behind uptake and transport of water. It is the process of water evaporation through openings called stomata. This creates a pull by replacing the water that has evaporated. This pulling in the xylem tissues would extend all the way down due to the cohesive forces. This negative water pressure that occurs in the roots will eventually result in an increase of water uptake from the soil.
The sun’s energy is strong enough to propel the water from the roots to the leaves. The heat from the sun causes the water to evaporate, setting the water chain in motion. To evolve into tall, self-supporting land plants, trees have to develop the ability to transport water from the soil to the tip that is at a staggering vertical distance. Now one might wonder how water could withstand the tensions pulled up by a tree. This is because water molecules stick to each other. Taking this strength into account, the loss of water at the top of a tree through transpiration provides the driving force to pull water and mineral nutrients up the trunks of trees as mighty as the redwoods.
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