vessel(redirected from Efferent vessels)
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(also trachea), in plants, a conducting element of xylem that consists of a long hollow tube formed by a single row of cells (vessel members) perforated on their transverse walls. Vessels are characteristic of angiosperms (except for certain Polycarpicae [Trochodendron, drimys] and Liliaceae [lily of the valley, dracena, agave]); they also occur in some ferns (Pleridium), selaginella, Equisetum, and Gneticae (ephedra, Gnetum, Welwitschia).
Vessels may be annular, helical, scalariform, or pitted, depending on the structures of their lateral walls. In annular and helical vessels the secondary membrane resembles rings or twisted ribbons. The vessels arise in the early stages of the development of plant organs and are capable of extension. Scalariform and pitted vessels with larger deposits of secondary membrane and bordered pits in the walls are formed in organs that have finished growing lengthwise. After the lignification of the membranes, the cell protoplasts die and the cavity of the vessel fills with water.
Primitive vessels were characterized by great length (reaching 1.3 mm) and small diameter; the lateral walls were marked by scalariform porosity (tulip tree), and the angular cross section of vessel members had scalariform perforations on sloped transverse walls. Highly specialized vessels are composed of short vessel members that in cross section are rounded and have a wide opening (reaching 0.5 mm in diameter). The vessel members have simple perforations on the transverse walls and small alternate pits on the lateral walls (ash, oak).
L. I. LOTOVA
What does it mean when you dream about a vessel?
A vessel in a dream may be the container that holds the dreamer’s valuables. The size and the condition of the vessel—e.g., old and tarnished or new and shiny—may indicate if these are established ideals or things newly acquired. Vessels can also be containers of the self.