The water columns in xylem tubes are under high tension as w

The water columns in xylem tubes are under high tension as water moves up the plant. This tension causes the water potential of this water to become which (more negative or less negative, SELECT ONE) at the tops of trees compared with the bases of trees.

If a water column is broken and an air bubble forms, what happens to water flow?

Solution

Answer

The water potential is expressed in negative and water will always move into the Ares of more negative water potential where tension is high. In xylem, the water moves upwards creating high tension due to evaporation. As water continuously moves into the xylem the water potential has to be more negative. So the water potential is more negative at the top of the tree compared to the bases (roots with least negative).

Therefore, the tension causes the water potential of the water to be more negative at the top compared to the bases.

When there is more tension in the xylem, the water vaporizes locally and dissolves air leading to cavitation. The formation of air bubble due to reduced solicit, the gases can expand and block the water. As xylem is interconnected the air bubble can be eliminated. Many plants develop a new xylem which becomes functional before the old xylem stops working. In the newly formed xylem, water can bypass the blocked point by passing through neighboring vessels.