Identify the elements of the tissue responsible for the translocation of food in plants and state each element’s function also.
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Answer:
The plant body is generally divided into roots, stem, and leaves. The roots are in the soil, which is the major source of nutrients in plants. Water and other nutrients enter the plant through the roots. The leaves are the food production centres. Using the sunlight and Carbon dioxide they synthesize food through photosynthesis in the chloroplasts.
Now, food from the leaves has to reach the other parts and the water, along with other nutrients has to reach leaves and other parts. All of this takes place through the vascular tissues of the plants. This is basically the transportation in plants.
You have already learned in earlier classes about the specialized cells and tissues in plants, which are the xylem and phloem. Together, they constitute the vascular structure in plants.
When talking about transportation in plants we must discuss Xylem and Phloem. Xylem and Phloem tissues are present throughout the plant. They begin at the root and then move up to the stem, branches, and leaves.
The xylem tissue transports water and minerals from the roots to the leaves whereas the phloem tissue transports food from the leaves to the other parts of the plant. Xylem tissue has tracheids and vessel elements. Phloem tissue has companion cells and sieve tubes.
When transpiration in plants occurs, water gets evaporated from the leaves. This results in more water being pulled from the root. This phenomenon explains how water moves up in the plants, against gravity, without the use of any pump! The flow of water in the xylem tissues is unidirectional. It moves up the stem from the roots. It occupies the centre of the vascular bundle.
The phloem, on the other hand, is responsible for the translocation of the nutrients like carbohydrates and amino acids from the leaves to other areas of the plants. Here, the flow is bidirectional. It moves up and down the stem. Phloem occupies the edge of the vascular bundle, as seen in the following figure. Food movement in the phloem occurs due to the pressure flow mechanism. The differences in the osmotic pressure help in the movement of food from the area of high concentration to areas of low concentration.