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Name: Kyra
Status: educator
Grade: K-3
Location: TX
Country: N/A
Date: 12/22/2005


Question:
Ho does water get transported through a stem of a plant or flower.


Replies:
A simplified answer:

Vascular plants (plants with tubes) have two sets of tubes that transports materials throughtout the plant's tissues. "Xylem" tubes carry water primarily and are designed to facilitate water upward from the roots. "Phloem" tubes carry sugar and other materials made with photosynthesis dissolved in water downward to feed the plant's tissues.

The mechanisms that allow water to move against gravity are interesting. Xylem tubes act a little like paper towels absorbing water against gravity. The roots concentrate absorbed water and create a pressure that helps force water upward. This is why cutting a rooted plant often shows signs of "bleeding". The main mechanism is the evaporation of water from the leaves of most plants. Water is polar and sticks together to a certain point and when water molecules evaporate, they pull on the water molecules behind them forming a chaining effect all the way to the roots.

Steve Sample



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