Water moves up a plant's stem as a result of A. the xylem...

Water moves up a plant's stem as a result of
A. the xylem pump; B. diffusion of water into roots; C. translocation of phloem sap; D. evaporation of water from the leaves; E. photosynthesis in xylem cells.

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Key Concepts

Cohesion-Tension Theory

The cohesion-tension theory explains how water moves upward in plants. It states that water molecules stick together due to cohesion and adhere to the walls of the xylem vessels through adhesion. This cohesive force, combined with the tension created by transpiration (water evaporation from leaves), enables the continuous column of water to be pulled upward against gravity.

Transpiration

Transpiration is the process whereby water evaporates from a plant’s leaves, particularly through openings called stomata. This evaporation creates a negative pressure within the leaf’s air spaces, which in turn pulls water upward through the plant’s vascular system. It is a critical component of the water transport mechanism in vascular plants.

Xylem Function

Xylem is a type of vascular tissue in plants responsible for the transport of water and dissolved minerals from the roots to the leaves. Its structure, featuring long tubes with supportive cell walls, facilitates the movement of water under the influence of negative pressure generated by transpiration.

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