Xylem and phloem are plant tissues that are arranged in the vascular bundle of the plant which is a transport system. However, they have many differences which are explained below.
Xylem tissue is a vessel that is hollow from inside with no cross-walls and is used for transporting water and mineral ions. Water is needed by the plant so it can perform photosynthesis and transpiration. It is found in the central region of vascular bundles in stems and roots and takes a large proportion of the plant. Xylem vessels have conducting cells which are actually dead cells when they mature and have no cellular contents or organelles. Also, they have lignin deposits due to which they have a good strength and give structural support to the plants. Other features of xylem vessels include tracheids, vessel elements, fibers, living xylem parenchyma cells and strong xylem sclerenchyma. The function of xylem vessels is to transport the water absorbed from the roots of the plant to the other parts of the plant in a unidirectional way (upwards towards the leaves) via the transpirational pull. It also provides the plants with mechanical support, so that they can remain upright.
Phloem tissue is an elongated living tissue with sieve tubes that translocates organic compounds like amino acids and sugars in the plant, from leaves or other green, photosynthesizing parts to the growing parts of plants like flowers and also storage parts like tubers in potatoes. They consist of a cytoplasm but do not have any nucleus as it can interfere with the bulk movement. It has sieve tubes, fibers and companion cells with many mitochondria that provide the energy for the bulk transport in the sieve tube elements. The sieve tube elements have pores between them (sieve plates) through which the nutrients pass. They form a small proportion of the total body of the plant, and are located in the outer parts of vascular bundles in roots and stems. As the phloem has to transport nutrients to flowers/ fruits (upwards) and roots/ tubers (downwards), they work in a bidirectional way. Phloem has no role in the mechanical support of plants, and has no lignin deposits. Instead, they just have cellulose cell walls.
To wrap up:
Xylem | Phloem |
A vessel that is hollow from inside with no cross-walls | An elongated living tissue with sieve tubes |
Transports water and mineral ions from roots to upper parts of plants; water is needed for photosynthesis and transpiration | Translocates organic compounds like amino acids and sugars in the plant, from leaves or other green, photosynthesizing parts to the growing parts of plants like flowers and also storage parts like tubers in potatoes. |
Found in the central region of vascular bundles in stems and roots and takes a large proportion of the plant | Form a small proportion of the total body of the plant, and are located in the outer parts of vascular bundles in roots and stems |
Have dead cells when mature and no organelles | Have living cells with no nucleus but includes mitochondria, ribosomes and ER |
Have lignin deposits | No lignin Deposits; only cellulose cell walls |
Provide structural support to plant | Provide no structural support to plant |
Unidirectional (only upwards) | Bidirectional (upwards and downwards) |
A passive process no energy needed | An active process; needs energy which is provided by the companion cells |
Tracheids, vessel elements, fibers, living xylem parenchyma cells and strong xylem sclerenchyma present | Sieve tubes, fibers and companion cells present
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