When leaves give off water vapor, what mainly helps new water move up from the roots?
Show answer & explanation
Answer: Pull from the leaves
Pressure from the roots — Root pressure can move some water, especially in small plants or humid conditions, but it is usually not the main force. When water evaporates from leaf pores, it pulls on the continuous water column inside xylem, drawing more water up from the roots.
Pull from the leaves ✓ — Water evaporating from leaf pores creates a pull at the top of the plant. Because water molecules cling to each other inside xylem, that pull travels down the column and helps lift water and dissolved minerals from the roots.
Waste leaving the leaves — Water vapor is not mainly a waste stream. The useful effect is the pull created by evaporation, which keeps water and minerals moving upward through the plant instead of simply dumping unwanted material out of the leaf.