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The presence of vessels in xylem has been considered to be one of the key innovations that led to the success of the flowering plants. It was once thought that vessel elements were an evolutionary innovation of flowering plants, but their absence from some basal angiosperms and their presence in some members of the Gnetales suggest that this hypothesis must be re-examined; vessel elements in ...
Angiosperms have both tracheids and vessel elements. [1] A tracheid is a long and tapered lignified cell in the xylem of vascular plants. It is a type of conductive cell called a tracheary element. Angiosperms use another type of conductive cell, called vessel elements, to transport water through the xylem.
Tracheids and vessel elements are distinguished by their shape; vessel elements are shorter, and are connected together into long tubes that are called vessels. [6] Xylem also contains two other type of cells: parenchyma and fibers. [7] Xylem can be found: in vascular bundles, present in non-woody plants and non-woody parts of woody plants
According to cohesion-tension theory, water transport in xylem relies upon the cohesion of water molecules to each other and adhesion to the vessel's wall via hydrogen bonding combined with the high water pressure of the plant's substrate and low pressure of the extreme tissues (usually leaves).
The blood vessels of the thyroid rest on the trachea next to the isthmus; superior thyroid arteries join just above it, and the inferior thyroid veins below it. [2] In front of the lower trachea lies the manubrium of the sternum , the remnants of the thymus in adults.
Xylem is the water-conducting tissue, and the secondary xylem provides the raw material for the forest products industry. [25] Xylem and phloem tissues each play a part in the conduction processes within plants. Sugars are conveyed throughout the plant in the phloem; water and other nutrients pass through the xylem.
Various forms of psychology concentrations are included in the sectors of health psychology, forensic psychology, clinical psychology, industrial and organizational psychology, and school psychology. Health psychology is a discipline that understands the psychological, behavioral, and cultural aspects that affect the physical health and ...
Edward B. Titchener is credited for the theory of structuralism. It is considered to be the first "school" of psychology. [3] [4] Because he was a student of Wilhelm Wundt at the University of Leipzig, Titchener's ideas on how the mind worked were heavily influenced by Wundt's theory of voluntarism and his ideas of association and apperception (the passive and active combinations of elements ...