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Plants and photosynthesis Before we look at food chains we will go over the way green plants capture energy from the Sun to make food. This is the start of all the food chains we will look at.

Plants and photosynthesis Animals eat food to get their energy. But green plants don't. Instead they make their own food, glucose, in a process called photosynthesis. We say that plants can photosynthesise. These are the things that plants need for photosynthesis: 

carbon dioxide

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water

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light These are the things that plants make by photosynthesis:



glucose

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oxygen We can show photosynthesis in a word equation, where light energy is shown in brackets because it is not a substance: carbon dioxide + water (+ light energy) → glucose + oxygen Plants get carbon dioxide from the air through their leaves, and water from the ground through their roots. Light energy comes from the sun. The oxygen produced is released into the air from the leaves. The glucose produced can be turned into other substances, such as starch, which is used as a store of energy. This energy can be released by respiration.

Where does photosynthesis take place? Photosynthesis takes place inside plant cells in small things calledchloroplasts. Chloroplasts contain a green substance called chlorophyll. This absorbs the light energy needed to make photosynthesis happen. Plants can only photosynthesise in the light.

Getting carbon dioxide, light and water that the equation for photosynthesis is: carbon dioxide + water (+ light energy) → glucose + oxygen Let's see how plants get the carbon dioxide and water they need for this process.

Carbon dioxide Plants get carbon dioxide from the air through their leaves. The carbon dioxidediffuses through small holes in the underside of the leaf called stomata. (One of these holes is called a stoma. The plural is stomata.)

The lower part of the leaf has loose-fitting cells, to allow carbon dioxide to reach the other cells in the leaf. This also allow the oxygen produced in photosynthesis to leave the leaf easily.

Light A leaf usually has a large surface area, so that it can absorb a lot of light. Its top surface is protected from water loss, disease and weather damage by a waxy layer. The upper part of the leaf is where the light falls, and it contains a type of cell called a palisade cell. This is adapted to absorb a lot of light. It has lots of chloroplasts and is shaped like a tall box.

Water

Turgid plant that's watered regularly and a flacid plant without enough water.

Plants get the water they need for photosynthesis through their roots.

The roots have a type of cell called a root hair cell - these project out from the root into the soil. Roots have a big surface area and thin walls, which allow water to into them easily. Note that root cells do not contain chloroplasts, as they are normally in the dark and cannot photosynthesise.

The water absorbed by the root hair cells es through the plant in xylem tubes, and eventually reaches the leaves. If a plant does not absorb enough water, it will wilt or go floppy. Without water it may also not photosynthesise quickly enough, and it may die.