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Like all living things, plants need air, water, energy from food, and a place to live. The parts of a plant help meet all of these needs.
Roots grow downward into the soil. Roots on most plants have root hairs, which are thin, hairlike cells. Root hairs absorb water and minerals from the soil. Roots also hold the plant in place. In some plants, roots also store food. A single, thick root is called a taproot. Dandelions, carrots, and grapevines all use taproots. Other plants, including most trees, use fibrous roots. These roots spread out into the soil. No one root is larger than another.
A plant’s stem grows above ground. The stem connects the roots below with the leaves above. It carries water, minerals, and other nutrients through tiny tubes. It also holds up flowers and leaves. Shrubs and trees have woody stems, which are thick and strong. Other plants have soft, green, bendable stems.
Leaves are the main food-making parts of the plant. A leaf’s veins are bundles of tubes that carry food and water. The outside of a leaf is a thin, protective layer called an epidermis. This helps keep the leaf from losing water. On the lower epidermis are tiny openings called stomata. Gases and water pass through these openings. Any extra water exits through the stomata in a process called transpiration.
Leaves make food with the help of chlorophyll, which traps energy from sunlight. They use this energy to combine water with a gas called carbon dioxide. The result is food, in the form of sugars, and oxygen gas. This food-making process is called photosynthesis.
The plant stores food until it is needed. Then its cells use oxygen to break apart sugars and release their energy. This process is called respiration. In many ways, respiration and photosynthesis are opposite processes.
Plants often need to save water. Oaks, maples, and other trees drop their leaves to save water during the winter. A cactus has a large, fleshy stem that stores water. The leaves of evergreens have thick outer layer and a wax coating. This helps to keep water inside.
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Plants are made up of different parts that work together in a system. A plant part consists of the stems, roots and leaves to help the plant survive. Leaves make food for the plant. The leaf has different functions for each of its parts. The epidermis protects the leaves. The chlorophyll is green and makes food. The stomata is the passage way for gases and water. Any excess water exits through the stomata in a process called transpiration. Roots take in materials a plant needs to make food. They also anchor the plant in the soil. There are two kinds of roots. Taproot is a single, thick root. Another root is a fibrous root which grows out into the soil. Root hairs are threadlike cells on a root that take in water and minerals from the soil. A stem carries food, minerals, and other nutrients to and from the roots and leaves. It supports the plant’s flowers. It holds the leaves up to the light.
Photosynthesis is the food-making process of the plant. Plants use the energy from the sunlight to make food from water and carbon dioxide. Oxygen is released into the air. The oxygen is used to break apart sugars and energy is given off. This is called respiration.
Evergreens and cacti are plants that can prevent water loss. The evergreen lives in a cooler environment. Its leaves have a thick outer layer and a wax coating. A cactus lives in a hot environment. The cactus has leaves that are sharp spines which lose little water through transpiration.
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