Cohesion drives continuous water column in xylem

Steps:

• Transpiration at leaves creates negative pressure, pulling water upward.
• Hydrogen bonds between water molecules maintain cohesion in the column.
• This cohesive force resists breakage, enabling ascent through xylem vessels.
• Adhesion to walls aids but cohesion primarily forces movement.

Why B is correct:

• Cohesion, defined as attraction between water molecules via hydrogen bonds, forms a continuous column pulled by transpiration without breaking.

Why the others are wrong:

• A: Adhesion to cellulose walls supports capillary action but does not force upward movement.
• C: Ionic bonds with minerals occur but do not create cohesion; minerals are transported dissolved, not bonding water.
• D: High latent heat slows evaporation but does not drive or force water movement through vessels.

Final answer: B