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Xylem and Phloem: Plant Transportation System

Updated on July 8, 2012
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Did you ever wonder how trees and other plants distribute food and water to themselves? They actually have an internal transportation system made up of tissues called xylem and phloem.

Xylem

Xylem is a specialized plant tissue that primarily carries water and nutrients throughout woody and non-woody plants. Its primary function is to carry water upward from the roots to the other parts of the plant.

Xylem is composed of long, tubular cells called “tracheids”, which are connected together by “vessels.” A process called transpiration drives the transport of water through the plant. Plants constantly release small amounts of water from their leaves when photosynthesis, the process by which plants use sunlight, water and carbon dioxide to create their own food, occurs.

As water evaporates from the plant’s leaves, the transpiration process works to pull the water up through the plants. The water and nutrients enter the plant through the roots and are pulled through the various layers of the plant’s cortex until it reaches the xylem tissue. Once the water and nutrients reach the xylem tissue, it is moved through the tracheids and vessels. Water and nutrients can then move laterally to reach other plant parts, such as the leaves.

Plant Tissue

Cross-section of plant tissue, showing the various layers of tissue
Cross-section of plant tissue, showing the various layers of tissue | Source

Phloem

Phloem is another specialized plant tissue that comprises the plant’s transportation system. Its primary function is to carry sugars created by photosynthesis to “feed” the various parts of the plant.

Photosynthesis occurs in the green leaves of plants. Plants use sunlight, water, and carbon dioxide to create sugars which serve as the plant’s energy source to carry out the processes it needs to live. It is the process that drives the sugars through the phloem tissue so that it can reach all the parts of the plant, including the tissue.

Phloem is composed of cells called sieve cells, which are the primary element for carrying the sugars through the plant. A process called osmosis brings water into the sieve cells and effectively pushes the plant sugars down through the plant for distribution.

Xylem and phloem comprise the food transportation system for vascular plants. They are essential in keeping the plant alive.

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    • ChristinS profile image

      Christin Sander 5 years ago from Midwest

      you learn something new everyday. What an interesting hub. I indeed have wondered how trees and plants distribute the nutrients/water throughout - and now I know. Voted up and interesting.