What keeps the force of gravity from overcoming transpirational pull?

• A. Upward pressure from the roots
• B. High water pressure in the leaves
• C. The Casparian strip blocking water molecules from moving out
• D. Movement of water toward a sugar sink
• E. Cohesion and adhesion of water molecules

Answer: (E)

Verified step by step guidance

1. Understand the concept of transpirational pull: Transpiration is the process where water evaporates from the leaves of plants, creating a negative pressure that pulls water upward from the roots through the xylem.
2. Recognize the role of cohesion: Cohesion refers to the attraction between water molecules due to hydrogen bonding. This property helps maintain a continuous column of water within the plant's xylem vessels.
3. Recognize the role of adhesion: Adhesion is the attraction between water molecules and the walls of the xylem vessels. This helps counteract the force of gravity by allowing water to 'stick' to the sides of the vessels as it moves upward.
4. Consider the combined effect of cohesion and adhesion: Together, these forces create a capillary action that supports the upward movement of water against gravity, ensuring that the transpirational pull is not overcome by gravitational forces.
5. Conclude that cohesion and adhesion are essential: These properties of water are crucial for maintaining the flow of water from the roots to the leaves, enabling the plant to transport nutrients and maintain its physiological processes.