Plants

Life science



7th grade Jr high



Chapter 1



Plants are the basis of the food pyramid for all living things, even other plants. They have always been very important to people, not only for food, but also for clothing, weapons, tools, dyes, medicines, shelter and a great many other purposes. Both humans and animals benefit from plants. We eat many different types of plants such as fruits and vegetables. We also use plants for our herbs. Plants are also used to manufacture many different products such as shampoos, rubber, paper, and camera film. In some countries, fermented sugar cane is used instead of gasoline.

Animals use plants in many different ways also. They eat many fruits and other plants. Many animals use plants for shelter. Plants also provide animals with protection from predators. The destruction of different plants sometimes leads to animals becoming endangered or extinct.

The basic structure of plants consists of roots, stem, leaves, flower and/or fruit or seeds. A flower is the part of the plant that makes the seeds. The main parts of a flower are the carpels and stamens. These parts are often found in the center of the flower. There are egg cells in the carpel and pollen cells in the stamen. All flowers have four basic parts: sepals, petals, carpels, and stamen. Different flowers have different numbers and shapes of these parts.

Most plants can be divided into one of two general categories: herbaceous or woody plants. Herbaceous plants have soft stems, while woody plants are tree-like. Herbaceous plants produce completely new stems each year. The approaching cold weather causes the new stems to die back to the ground.

Some herbaceous plants survive periods of cold by forming underground bulbs, or tubers used for food storage. Many herbaceous plants complete their life cycles within one growing season and the whole plant dies, even the roots. These annuals produce seeds that will form new plants the next year.

Land plants are divided into two groups based on whether they have vascular tissues or not. All nonvascular plants are placed in one division. There are nine divisions of vascular plants. These are divided based on whether they form seeds or not.



Division Bryophyta - nonvascular plants

Class - Musci - the mosses

Division Pterophyta - ferns, group of seedless plants

Division Coniferophyta - cone-forming seed plants

Division Anthophyta - fruit-forming seed plants

Class - Monocotyledonae

Class - Dicotyledonae



Chapter 2



ROOTS



Roots help to anchor a plant in the ground. They also absorb water and minerals from the soil, and store food. Plants generally conform to one of two root systems, a taproot system or a fibrous root system.

A taproot system, generally found in dicotyledons, is made up of a central, large root that is called the taproot. The taproot is larger in diameter than the lateral roots. Lateral roots, which come from the pericycle, branch off from the taproot, and then lateral roots, can branch off other lateral roots. Taproots generally grow more deeply into the soil than do fibrous roots.

Unlike the taproot system, the fibrous root system is made up of thin, stringy roots that all have about the same diameter. These roots branch several times and form a complex mat under the plant that binds to the upper soil layers. Fibrous roots can be found in monocots such as grasses.

Some plants, such as the tomato plant, can have a fibrous root system or a taproot system depending on how the plant was grown. If the plant is grown from a seed, the plant will grow from a taproot. When the plant is grown from cuttings, a fibrous root system will form.

Every root grows a mass of tiny hairs near its tip to absorb water from the soil. These tiny hairs are called root hairs, and they are made from cells. They take water to the main root. The main root brings the water to the main plant. The roots also help hold the plant in the ground.

The inside of a root has four different parts. The epidermis is the outside part. It is like our skin. It protects the inside parts of the root, like our skin protects us. Plants take in water from the soil through their roots. The water passes through the vascular rays until it reaches the center of the root, the stele. This is where the veins are located.