Final answer:
Plants developed adaptations to supply water to all cells when they transitioned from water to land, including vascular tissues and a root system.
Step-by-step explanation:
The ancestors of land plants faced the challenge of supplying water to all cells of the organism when they transitioned from water to land. To overcome this challenge, plants developed adaptations such as vascular tissues, specifically xylem and phloem, which conduct water and nutrients throughout the plant. Additionally, plants evolved a root system to absorb water from the soil and provide support to the shoot. These adaptations allowed plants to distribute water to all cells, even in a dry land environment.