Location of Phloem and Xylem Tissues
The xylem and phloem make up the plants' vascular system, transporting substances to all parts of the plant. The location of these tissues is relevant to their functions in supporting the plant as it grows and in providing a transport system.
Roots
In the roots, the xylem and phloem are located in the center to provide support to the root as it pushes through the soil. Root hairs are present to absorb water and minerals, and the xylem and phloem aid in the distribution of these nutrients throughout the plant.
Leaves
The xylem and phloem form a network of veins in the leaves, providing support to the thin leaves and aiding in the transport of substances throughout the plant.
Stem
In the stem, the xylem and phloem are located near the outside to provide scaffold-like support for the plant. These tissues form tubes that transport sugars and other important substances throughout the plant.
Phloem Tissues
Phloem tissue is responsible for transporting solutes, mainly sugars, around the plant. It contains phloem fibers, sieve tube elements, phloem parenchyma, and companion cells. The sieve tube elements lack organelles and have a thin layer of cytoplasm, which reduces bending and aids in the transport of solutes. Companion cells provide the energy for the active transport of solutes, supporting both themselves and the sieve tube elements.
Xylem and Water Transport
Xylem tissue is responsible for transporting water and mineral ions in solution through the plant, from the roots to the leaves. The xylem vessels, which are long, tube-like structures formed by cells joined end to end, have thickened walls to support the transport of water and minerals. The cells are dead and contain no cytoplasm, and the walls are thickened with lignin, which prevents them from collapsing and allows flexibility.
Adaptations of Xylem Vessels
The xylem vessels lack end walls, creating an uninterrupted tube that allows water to pass through easily. The amount of lignin in the vessels increases with age, providing long-term support and preventing them from breaking.
Water Movement in Plants
Water enters the plant through the roots via osmosis, and travels through the xylem to the leaves, where it exits the xylem and enters surrounding cells. Water evaporates from the cell walls and diffuses out of the leaf into the surrounding air, a process known as transpiration. The evaporation of water from a plant's surface drives the movement of water throughout the plant, creating a tension that pulls more water into the leaf and ultimately aiding in the transportation of water and nutrients.
Transpiration Rate
Transpiration is the rate of loss of water from a plant, measured in grams per square centimeter per hour. It occurs due to the constant evaporation of water from the leaves, leading to the movement of water through the plant from roots to leaves.
In summary, the xylem and phloem play crucial roles in transporting water, nutrients, and solutes throughout the plant, supporting its growth and development. The adaptations and functions of these tissues are essential for the overall health and survival of the plant.
