Introduction

Around 450 million years ago, during the Ordovician period, plants began moving from their long-established aquatic world onto newly formed land. This new environment was harsh: unlike water, where dissolved minerals and moisture surrounded every cell, land offered water only deep within the soil, and plants had to develop entirely new means of drawing it upward. The evolution of an internal water-conducting system - what we now call vascular tissue - was one of the pivotal steps in the diversification of the plant kingdom, enabling the spread of early pteridophytes, then gymnosperms, and eventually today's flowering plants. But building this plumbing created its own challenge: lifting water many metres upward, against gravity, from root to leaf-tip. This chapter follows that entire journey - the physical and biological mechanisms governing how water travels from where it is absorbed in the roots to where it is lost from the leaves, how minerals dissolved in that water reach every tissue, and how the food manufactured during photosynthesis in the leaves is, in turn, carried back down to storage and utilization sites throughout the plant, against comparable structural and physiological challenges.