In vascular plants, xylem is a type of tissue that transports water and some minerals from the roots to the leaves. The other type of transport tissue is phloem, which transports sucrose and some other nutrients throughout the plant. The vascular tissues that translocate throughout the plant, xylem and phloem, classify vascular plants. Xylem tissue transports water from roots to stems and leaves, but it also transports other dissolved compounds. Phloem is in charge of transporting photosynthesis-produced food from leaves to non-photosynthesizing parts of the plants such as roots and stems.
Tracheary elements
Tracheary elements are the xylem’s specialized water and salt conducting cells. These have become elongated and lignified. They have a thick secondary wall with numerous pits. At maturity, these are non-living cells.
Members of the vessel
Vessel members are tracheary elements that are short, wide, and have perforated end walls. End to end, these connect to form long xylem vessels. Perforation plates are vessel endplates with perforations.
The secondary walls of vessels vary in thickness. These can be annular, spiral, scalariform, or reticulate in shape.
Tracheid
Tracheids are tracheary elements that are elongated tube-like with tapering ends. They don’t have perforated plates. Water flows from one tracheid to the next via pit membranes. These are dead empty cells with no cellular contents and an empty lumen. Their primary function is water conduction, but they are also involved in plant support.
Tracheids are elongated cells in vascular plants that transport water and mineral salts through the Xylem. Tracheids are one of two tracheary element groups. The other category is vessel elements. Tracheids, unlike vessel components, do not have perforation plates. Because Tracheids are single-celled organisms, their maximum capacity may be limited. Tracheary elements are a distinguishing feature of vascular plants that set them apart from non-vascular plants. Tracheids serve two purposes: they help with transportation and they provide structural support.
Function of xylem
The primary purpose of xylem is to carry water and some soluble nutrients such as minerals and inorganic ions from the roots to the rest of the plant. Xylem cells form long tubes through which materials are transported, and the mixture of water and nutrients that runs through the xylem cells is known as xylem sap. Because these molecules are conveyed passively, there is no need for energy. Capillary action is the phenomenon that causes xylem sap to flow upwards despite gravity. This happens when surface tension causes liquid to rise. Water is also helped to move up the xylem by sticking to the xylem cells. However, as a plant grows taller, it becomes more difficult to work against gravity to move materials, hence xylem limits the growth of tall trees.
Plants evolved from xylem over 400 million years ago. Plants must absorb carbon dioxide from the atmosphere as well as water from the soil in order to produce food through photosynthesis. When the stomata (small holes in the leaves of plants) are open to allow CO2 in, a lot of water evaporates, far more than the amount of CO2 taken in. Plants that established water transport systems to photosynthetic sites on leaves had a better chance of survival.
Structure of xylem
Xylem is made up of various cell kinds. Tracheids are lengthy cells that aid in the movement of xylem sap as well as structural support. Vessel elements are shorter than tracheids, but they also aid in water conductivity. They can be present in blooming plants but not gymnosperms such as pine trees. Perforation plates on vessel elements join each vessel element to create one continuous vessel.
Conclusion
Xylem tissue is made up of a network of dead, hollow elongated conduits like tracheids or vessels that can come into contact with living phloem or parenchyma tissue. The xylem is the central component of the soil, plant, atmosphere continuum (SPAC), extending from the roots to the leaves, and is responsible for moving water throughout the plant body from areas of high water availability (roots) to areas of low availability of water (leaves) (leaves). Water evaporates from the leaf mesophyll tissue to the atmosphere through the open stomata in a transpiring plant, with drier atmospheres causing higher rates of water loss.