Plants

Plant Food Production

Another difference between plants and animals is that plants can produce their own food, while animals eat either plants or other animals. The roots, stems, and leaves of plants are used to manufacture food. Roots take in water and minerals like calcium, iron, nitrogen, phosphorous, and potassium, then use these and other chemicals to make food. In order to do so, the water and nutrient chemicals have to reach the leaves. Because the nutrients travel through the stem of the plant the process can be a long journey in tall trees. In most cases the stem has vascular tissue through which the nutrients travel. As the water moves from one cell to another it eventually reaches xylem, which is a complex plant tissue. Xylem is formed into long tubes or vessels through which the water carries dissolved salts of the nutrient chemicals.

Eventually the fresh nutrient supply reaches the leaves of the plant. At the same time, food from the leaves of the plant, often in the form of some type of sugar, moves down the xylem in a liquid watery solution in tube-like cells called sieve cells. These cells have little holes in the wall of the tube that act like a sieve, allowing food to pass to the plant. The sieve cells are supported by phloem cells. These are plant tissues that are in parallel with the xylem tissues. A third type of plant tissue called cambium separates them. This tissue provides support and also keeps the nutrient solution separate from the food solution.

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