Tracheids are elongated cells The cell is the functional basic unit of life. It was discovered by Robert Hooke and is the functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. Some organisms, such as most bacteria, are unicellular . Other organisms, such as humans, in the xylem In vascular plants, xylem is one of the two types of transport tissue, phloem being the other. The word "xylem" is derived from classical Greek ξυλον , "wood", and indeed the best-known xylem tissue is wood, though it is found throughout the plant. Its basic function is to transport water but it also transports some of vascular plants Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the ferns, clubmosses, flowering plants, conifers and other gymnosperms. Scientific names for the group include Tracheophyta and Tracheobionta, but neither name is very widely used.[ that serve in the transport of water and mineral salts. Tracheids are one of two types of tracheary elements, vessel elements A vessel element is one of the cell types found in xylem, the water conducting tissue of plants. Vessel elements are typically found in the angiosperms but absent from most gymnosperms such as the conifers being the other. All tracheary elements develop a thick lignified cell wall, and at maturity the protoplast Protoplast, from the ancient Greek πρῶτον + verb πλάθω or πλάττω (to mould: deriv. plastic), initially referred to the first organized body of a species has broken down and disappeared. The presence of tracheary elements is the defining characteristic of vascular plants to differentiate them from non-vascular plants Non-vascular plants is a general term for those plants without a vascular system . Although non-vascular plants lack these particular tissues, a number of non-vascular plants possess tissues specialized for internal transport of water.... Tracheid build varies by location.
The two major functions that tracheids may fulfill are
- part of the transport system
- structural support
In most cases, the prime function of tracheids is transporting water. They occur in vascular bundles A vascular bundle is a part of the transport system in vascular plants. The transport itself happens in vascular tissue, which exists in two forms: xylem and phloem. Both these tissues are present in a vascular bundle, which in addition will include supporting and protective tissues. Also, it is a vein in the leaf that contains conducting tissues throughout the non-woody parts of the vascular plant and provide water and minerals collected by the roots to leaves and other parts of the plant (stem, flowers, fruits etc).
A good example of structural support is in softwoods The term softwood is used to describe wood from conifers. It may also be used to describe these trees, which tend to be evergreen, notable exceptions being bald cypress and the larches where tracheids are the major cell type. Tracheids give softwood its strength.
Because tracheids have a much higher surface to volume ratio compared to vessel elements, they serve to hold water against gravity (by adhesion Adhesion is any attraction process between dissimilar molecular species that can potentially bring them in "direct contact".[clarification needed] By contrast cohesion takes place between similar molecules) when transpiration Transpiration is a process similar to evaporation. It is the loss of water vapor from parts of plants , especially in leaves but also in stems, flowers and roots. Leaf surfaces are dotted with openings called, collectively, stomata, and in most plants they are more numerous on the undersides of the foliage. The stoma are bordered by guard cells is not occurring. This is likely one mechanism that helps plants prevent air embolisms An air embolism, or more generally gas embolism, is a pathological condition caused by gas bubbles in a vascular system. The most common context is a human body, in which case it refers to gas bubbles in the bloodstream . However air embolisms may also occur in the xylem of vascular plants, especially when suffering from water stress.
See also
- Vessel element A vessel element is one of the cell types found in xylem, the water conducting tissue of plants. Vessel elements are typically found in the angiosperms but absent from most gymnosperms such as the conifers
- Xylem In vascular plants, xylem is one of the two types of transport tissue, phloem being the other. The word "xylem" is derived from classical Greek ξυλον , "wood", and indeed the best-known xylem tissue is wood, though it is found throughout the plant. Its basic function is to transport water but it also transports some
References
- Wilson, K. & D.J.B. White (1986). The Anatomy of Wood: its Diversity and variability. Stobart & Son Ltd, London
External links
- Pictures of softwood tracheids in cross section and in maceration; both in pine.
Categories: Plant anatomy Plant anatomy is that field in botany that needs to cut into plants to be able to study its subject, as opposed to "plant morphology" that can study its subject without resorting to a knife | Plant physiology Plant physiology is the study of the function, or physiology of plants. Fundamental processes such as photosynthesis, respiration, transpiration, and floral inducation are studied by plant physiologists
