Which of the following statements does not hold true in context of apoplast?

The correct answer is crosses cell membrane.

To understand why this statement does not hold true for the apoplast, let us break down the concept of apoplastic pathway step-by-step:

1. Definition of Apoplast: The apoplast is the space outside the plasma membrane of plant cells. It consists of the non-living parts of a plant, primarily the cell walls, intercellular spaces, and the lumen of xylem vessels.

2. Characteristics of Apoplastic Movement:
- Occurs through intercellular spaces and cell walls: Water and solutes move exclusively through the cell wall material and intercellular spaces. Since these spaces are outside the living protoplasm, the movement is passive and driven by gradient and capillary action.
- Continuous path: The system of adjacent cell walls is continuous throughout the plant body, except at certain specialized barrier regions.
- Discontinuous at Casparian strips: In the endodermis of roots, the cell walls contain a band of suberin called the Casparian strip. Suberin is impervious to water, making the apoplastic pathway discontinuous at this point. To cross the endodermis, water must enter the living cytoplasm by crossing the cell membrane, switching to the symplastic pathway.

3. Why the correct option does not hold true:
Since the apoplast is defined as the system of non-living, extracellular components, water and solutes moving through it do not cross any cell membrane or enter the cytoplasm during their journey (until they reach the Casparian strip). Crossing the cell membrane is the defining feature of the symplastic pathway, not the apoplastic pathway. Therefore, the statement "crosses cell membrane" is false in the context of the apoplast.