FLOWERING PLANT

Trace the pathway in a flowering plant as the water moves from

the soil through the tissues of the root, stem, and leaves to the atmosphere. Explain the mechanisms involved in conducting water through these tissues. A very basic overview of water through a flowering plant starts at the roots. The roots absorb water and dissolved minerals from the soil. The roots exchange gases with the air spaces of soil, taking in oxygen and discharging carbon dioxide. This gas exchange supports the cellular respiration of root cells. Water and mineral are transported upward within the xylem, from the roots into the shoot system. Transpiration from the evaporation of water from leaves (mostly through the stomata) creates a force within leaves that pulls xylem sap upward. Leaves also an exchange gas through the stomata taking in carbon dioxide that provides carbon for photosynthesis and expelling oxygen. Sugar is produced by photosynthesis in the leaves and is transported within the phloem to roots and other non photosynthetic parts of the plant. Most absorption of water and minerals occurs near root tips, where the epidermis is permeable to water and where root hairs are located. Root hairs account or provide for most of the surface area of roots. The hairs adhere tightly to soil particles, which are usually coated with water and dissolved minerals. The soil solution flows into the hydrophilic walls of the epidermal cells and passes freely along the apoplast into the root cortex. This exposes the cells of the cortex called the parenchyma cells the soil solution. So the membrane for the uptake of water and minerals has greatly increased into the cytoplasm than the surface area of the epidermis alone. As the soil solution moves along the cell walls, some of the water and the cells of the epidermis and cortex take up solutes, this is where the pathways switch from the apoplast to the symplast.