What are Plants?
Autumn. A time when leaves turn amazing colors. Of course, leaves are part of plants. But what are plants? What separates a plant from a fungus or protist? Or animal?
How Do Plants Obtain Food?
Almost all plants make food by photosynthesis. Only about 1 percent of the estimated 300,000 species of plants have lost the ability to photosynthesize. These other species are consumers, many of them predators. How do plants prey on other organisms? The Venus fly trap in Figure below shows one way this occurs.
Venus fly trap plants use their flowers to trap insects. The flowers secrete enzymes that digest the insects, and then they absorb the resulting nutrient molecules.
What Do Plants Need?
Plants need temperatures above freezing while they are actively growing and photosynthesizing. They also need sunlight, carbon dioxide, and water for photosynthesis. Like most other organisms, plants need oxygen for cellular respiration and minerals to build proteins and other organic molecules. Most plants support themselves above the ground with stiff stems in order to get light, carbon dioxide, and oxygen. Most plants also grow roots down into the soil to absorb water and minerals. And, of course, we need the energy stored in plants through photosynthesis to survive. Life as we know it would not be possible without plants.
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.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.Pollination:
The movement of pollen from one plant to another. Pollination is necessary for seeds to form in flowering plants.
What’s the difference between a fruit and a vegetable?
Foods we often call vegetables when cooking are really fruits because they contain seeds inside.
Play a Plant Parts Game!
What Do Different Plant Parts Do?
Plant parts do different things for the plant.
Roots act like straws absorbing 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. They can also store sugars and carbohydrates that the plant uses to carry out other functions. Plants can have either a taproot system (such as carrots) or a fibrous root system (such as turf grass). In both cases, the roots are what carries the water and nutrients needed for plants to grow. The cells that do this work are called the xylem cells. They move water. The phloem cellsmove the food. Stems also provide support for the plant allowing the leaves to reach the sunlight that they need to produce food. Where the leaves join the stem is called the node. The space between the leaves and the stem is called the internode.
Stems 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. They are like tiny tubes that can carry things around that the plant needs.
|A celery stalk, the part of celery that we eat, is a special part of the leaf structure called apetiole. A petiole is a small stalk attaching the leaf blade of a plant to the stem.||In celery, the petiole serves many of the same functions as a stem. It’s easy to see the “pipes” that conduct water and nutrients in a stalk of celery.||Here the “pipes” are dyed red so you can easily see them.|
Most 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.
A compound leaf is a leaf made up of separate leaflets attached by a petiole to the stem like an ash or a locust.
Leaves are made to catch light and have openings to allow water and air to come and go. The outer surface of the leaf has a waxy coating called acuticle which protects the leaf. Veins carry water and nutrients within the leaf.
Leaves are the site of the food making process calledphotosynthesis. In this process, carbon dioxide and water in the presence of chlorophyll (the green pigment) and light energy are changed into glucose (a sugar). This energy rich sugar is the source of food used by most plants.
Photosynthesis is unique to green plants! Photosynthesis supplies food for the plant and oxygen for other forms of life.
A green plant helped make the oxygen you are breathing today.
Flowers are used to reproduce the plant. Flowers contain pollen and tiny eggs called ovules. After pollination of the flower, the ovule develops into a fruit.
Fruit provides a covering for seeds. Fruit can be fleshy like an apple or hard like a nut.
Seeds contain new plants. Seeds form in fruit.