14.2 Vascular Plant Systems
Think about how your body systems work.
your circulatory system transports food, oxygen, water, minerals, and other materials throughout your body.
Your circulatory system is made up of many different cells, tissues, and organs.
All parts of the system work together. Your circulatory system also interacts and works with other systems of your body.
Vascular plants also have systems.
The shoot system is the aboveground part of the plant. Below the ground is the root system. Each system is made of cells, tissues, and organs working together.
Water, Sugar, and Mineral Transport
Vascular tissue forms a plant's pipeline, connecting the root system and the shoot system.
One part of the vascular tissue is a set of linked cells called the xylem
(ZYluhm). The xylem forms a pipeline for water and minerals. From the root system, water and minerals travel upward through the xylem to the shoot system.
Some water is used in photosynthesis, but most of it evaporates through stomates in the leaves.
The loss of water through the stomates of leaves is called transpiration.
A leaf is a shoot system organ.
Leaves capture light and make glucose by photosynthesis. Glucose made in the leaves must reach other parts of the plant. A second set of linked cells in the vascular tissue, called the phloem (FLOHehm), transports glucose and other sugars.
In the root system, the sugars provide energy for root growth.
The shoot system receives sugars for growth and flower production. The plant storage organs store glucose in the form of starch and cellulose for later use.
Root System The root system of a plant is usually about the same size
as its shoot system. For example, a corn plant 2 m tall often has roots that are 2 m long and extend 1 m on all sides.
Root Functions Roots support and anchor the plant.
Roots absorb water and minerals from the soil. Roots store glucose in the form of starch.
Root Structure At the tip of the growing root is a dome-shaped root cap.
Tiny structures called root hairs project near the tip
Tiny structures called root hairs project near the tip. Root hairs increase the area of root exposed to the soil. The greater the exposed surface area, the easier it is for the root to absorb needed water and minerals.
The root hairs extend from the epidermis (EHP uh DUR mihs)
The root hairs extend from the epidermis (EHP uh DUR mihs). The epidermis is an outer layer of protective cells.
Beneath the epidermis is a starch storage layer.
In the center are the xylem and phloem.
Between the xylem and phloem is the cambium (KAM bee uhm)
Between the xylem and phloem is the cambium (KAM bee uhm). The cambium is growth tissue that makes new xylem and phloem cells.
Roots and Soil Formation
In rocky environments, plant roots make soil by breaking apart solid rock. The root cap secretes acid-containing slime that dissolves rock. The force of the root growth wedges the rock apart. As fallen leaves and other plant parts decay and mix with the rock fragments, soil forms.
Root Types Although plant roots vary in size and structure, there are three general types: fibrous roots, taproots, and aboveground roots.
Fibrous Roots Fibrous roots branch out in all directions.
Fibrous roots absorb water efficiently from near the ground surface. They also hold soil together, preventing erosion
Taproots A taproot is a thick main root that grows straight into the ground. Smaller roots grow out from the sides. A taproot securely anchors a plant in the soil and may store starch. Vegetables such as carrots and beets are taproots. They contain starch stored by the plants.
Aboveground Roots Many rain forest plants grow high in trees.
They have aboveground roots that cling to the tree and absorb water and nutrients. Other aboveground roots start on the plant stem and grow down into the soil. They support large trees.
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