Plant-Soil Interactions

Plant Parts and Functions

Roots

• Plants use their root systems for structural support, stability and nourishment.

• The primary function of the root system is to absorb water and nutrients from the soil.

•Roots may stop growing during the winter, not because they have become dormant like the buds at the top of the plant, but rather because the temperature is too cool to support growth. In order for roots to grow, they must have adequate moisture and temperature.

•Water is absorbed by the root hairs and brings along with it any chemicals, including nutrients that are dissolved in it.

• From here, the water and nutrients enters the plant’s vascular system.

The Vascular System

• The plant stem contains a vascular system that connects the leaves to the roots. • The vascular system is composed of xylem

tissue that transports water from the roots to the rest of the plant and phloem tissue that transports sugars produced in the leaves to the nonphotosynthetic parts of the plant.

• The xylem is composed of dead cells that form long, empty tubes.

• Water is thought to move through the xylem by a process known as cohesion-tension. According to this view, water can be pulled upward provided that the diameter of the tube is sufficiently small and that the column of water is continuous, that is, without air bubbles. A further requirement is that the tube be made of a material to which water molecules will adhere. Within each xylem tube, the water molecules are attracted to adjacent water molecules, forming an unbroken chain.

• The plant loses water through evaporation from its leaves by a process called transpiration.

• As water is lost, a negative pressure or tension is created that pulls water up from the xylem. Transpiration is the process that drives the transport of water from the roots up through the stems to the leaves.

Plant Parts and FunctionUse worksheet to complete notes on.

RootsRoots absorb water and minerals from the soil. Tiny root hairs stick out of the root, helping in the absorption. Roots help to anchor the plant in the soil so it does not fall over. Roots also store extra food for future use.

StemsStems do many things. They support the plant. They act like the plant's plumbing system, conducting water and nutrients from the roots and food in the form of glucose from the leaves to other plant parts. Stems can be herbaceous like the bendable stem of a daisy or woody like the trunk of an oak tree.

Herbaceous: Plants with stems that are usually soft and bendable. Herbaceous stems die back to the ground every year.

Woody: Plants with stems, such as tree trunks, that are hard and do not bend easily. Woody stems usually don't die back to the ground each year.

LeavesMost plants' food is made in their leaves. Leaves are designed to capture sunlight which the plant uses to make food through a process called photosynthesis.Photosynthesis:A process by which a plant produces its food using energy from sunlight, carbon dioxide from the air, and water and nutrients from the soil.

FlowersFlowers are the reproductive part of most plants. Flowers contain pollen and tiny eggs called ovules. After pollination of the flower and fertilization of the ovule, the ovule develops into a fruit.Pollination: The movement of pollen from one plant to another. Pollination is necessary for seeds to form in flowering plants.

FruitFruit provides a covering for seeds. Fruit can be fleshy like an apple or hard like a nut.

SeedsSeeds contain new plants. Seeds form in fruit.