The cells that form the structures that allow carbon dioxide to enter the leaf are the Question 13 (1 point) In the theory of phloem movement in plants, a "sink" may be a meristem, a companion cell, or a root. a cell carrying out photosynthesis. )a sieve cell, a companion cell, or a leaf. a meristem, a tuber, or a root. Question 14 (1 point) The movement of the surface of a liquid along the surface of a solid is an example of tonicity. O capillary action. active transport. () cohesion