Plant Systems PDF

# Chapter 1 | Plant Systems ## Roots A root system comprises the roots of the plant and holds a plant in place in the ground. It also takes in the water that is needed by the plant. Most plants have roots with a root cap, which covers and protects the tip of the root as it grows deeper in the soil...

# Chapter 1 | Plant Systems ## Roots A root system comprises the roots of the plant and holds a plant in place in the ground. It also takes in the water that is needed by the plant. Most plants have roots with a root cap, which covers and protects the tip of the root as it grows deeper in the soil. The outer surface of a root is made up of epidermis cells which are thin walled and sometimes grow out into long delicate root hairs. ### Types of Root Systems There are two types of root systems: * **Taproot:** A taproot is a long, thick root that grows straight down. A carrot is a good example of a taproot. * **Fibrous root system:** A fibrous root system consists of many roots growing in all directions. ## Shoot System * A shoot system is made up of all the parts that are above the ground. These are: >* **Stem:** The stem is a plant's main support above the ground. It holds the leaves so they can get light for photosynthesis, and the flowers to attract insects. >* **Leaves:** Leaves are where a plant makes its food during photosynthesis. Leaves come in different shapes and sizes. >* **Flowers:** Flowers contain the reproductive organs of a plant. There are many types of flowers, but most of them have brightly colored petals and are sweet-smelling. >* **Buds:** Buds are the site(s) of new growth. Growth takes place at the tips of roots and shoots. # Transport in Plants Roots and stems are plant organs which contain the transport system of a plant. They have thin tubes inside them which carry liquids up and down the plant. There are two kinds of tubes: xylem and phloem (collectively called vascular tissues). Xylem and phloem tubes are bundled together in vascular bundles. ## Transport of Water and Minerals Xylem tubes carry water and minerals in solution from the soil up to the parts of the plant above the ground. They have thickened, strong walls which help to support the plant. Xylem is dead tissue. In plants such as trees, new xylem is made each year forming rings in the trunk. Xylem is wood! ## Transport of Food Phloem tubes are made from living cells joined end to end. They carry sugar solution from the leaves, where it is made during photosynthesis, to every other part of the plant. There are holes at the end of each phloem cell so sugar solution can pass through. ## Inside a Root * **Water and minerals** move up the xylem tubes to the stem. * **The cortex of a root hair** is composed of unspecialized cells present between the epidermis and the vascular tissues. * **Root hairs** give a big surface area to take in water and minerals from the soil. ***Root hairs** help in absorbing water. ## Inside a Stem * **A vascular bundle** is made of xylem and phloem tubes. These cells make new xylem and phloem as the plant gets bigger. * **Epidermis** is the outermost layer of cell which make up the stem. In woody plants, there is a layer of cork cells called bark on top of the epidermis. * **Cortex** is present between the epidermis and the vascular tissue in a stem. It may store carbohydrates, resins, latex, oils, or tannins of the plant. ## Xylem & Phloem * **Xylem** tubes carry water and minerals up from the roots. These tubes have strong, thick walls. * **Phloem** tubes carry sugar made in the leaves up and down the plant. These tubes have thin walls. ## Test Yourself 1. What is a transport system? 2. What is a vascular bundle? 3. How are xylem and phloem tissue a) the same? b) different? 4. Explain how xylem tubes help support a plant. 5. What happens at the root tip? 6. What is the job of the root cap? **Sugar mixes with water to make a strong sugar solution which is transported in the phloem tubes out of the leaves and into the stem. From there it may either go up to growing shoots or down to the roots, in two directions at a time. The speed and direction of the movement of sugar solution depends on how much is needed by certain parts of the plant and when. In spring, when shoots are growing, most of the sugar solution goes to the growing shoots. In the autumn, a lot of sugar is stored so it goes up to fruits and seeds or down to the roots.**