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Vascular tissue

From Wikipedia, the free encyclopedia

Cross section of celery stalk, showing vascular bundles, which include both phloem and xylem.
Cross section of celery stalk, showing vascular bundles, which include both phloem and xylem.
Detail of the vasculature of a bramble leaf.
Detail of the vasculature of a bramble leaf.

Vascular tissue is a complex conducting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue are the xylem and phloem. These two tissues transport fluid and nutrients internally. There are also two meristems associated with vascular tissue: the vascular cambium and the cork cambium. All the vascular tissues within a particular plant together constitute the vascular tissue system of that plant.

The cells in vascular tissue are typically long and slender. Since the xylem and phloem function in the conduction of water, minerals, and nutrients throughout the plant, it is not surprising that their form should be similar to pipes. The individual cells of phloem are connected end-to-end, just as the sections of a pipe might be. As the plant grows, new vascular tissue differentiates in the growing tips of the plant. The new tissue is aligned with existing vascular tissue, maintaining its connection throughout the plant. The vascular tissue in plants is arranged in long, discrete strands called vascular bundles. These bundles include both xylem and phloem, as well as supporting and protective cells. In stems and roots, the xylem typically lies closer to the interior of the stem with phloem towards the exterior of the stem. In the stems of some Asterales dicots, there may be phloem located inwardly from the xylem as well.

Between the xylem and phloem is a meristem called the vascular cambium. This tissue divides off cells that will become additional xylem and phloem. This growth increases the girth of the plant, rather than its length. As long as the vascular cambium continues to produce new cells, the plant will continue to grow more stout. In trees and other plants that develop wood, the vascular cambium allows the expansion of vascular tissue that produces woody growth. Because this growth ruptures the epidermis of the stem, woody plants also have a cork cambium that develops among the phloem. The cork cambium gives rise to thickened cork cells to protect the surface of the plant and reduce water loss. Both the production of wood and the production of cork are forms of secondary growth.

In leaves, the vascular bundles are located among the spongy mesophyll. The xylem is oriented toward the adaxial surface of the leaf (usually the upper side), and phloem is oriented toward the abaxial surface of the leaf. This is why aphids are typically found on the undersides of the leaves rather than on the top, since the phloem transports sugars manufactured by the plant and they are closer to the lower surface.[citation needed]

YouTube Encyclopedic

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Transcription

In order for a tree to carry out photosynthesis and Maintain its overall health Water and Nutrients need to move throughout the entire tree even against gravity how does a plant manage this without an organ like a heart that pumps fluids as We will see water is pulled from the roots to the leaves through a process called transpiration in addition water potential drives the movement of water from [one] area of the plant to another using Osmosis Gravity and the Surface tension of water Transpiration begins in the leads the arrangement of cells and structures in the leaf facilitate the movement of gases and water into and out of the leaf a leaf contains several layers of specialized cells The upper Epidermis is one cell layer [thick] and provides a protective covering Below that layer is mesophyll tissue Cells in the palisade mesophyll layer are sites for photosynthesis and secretion as well as storage of food and water the spongy mesophyll layer contains a looser arrangement of cells where spaces between cells aid in gas exchange and the passage of water vapour from [the] leaves Throughout the lower epidermal tissue are stomata which are microscopic openings flanked by guard cells? Gases pass into and out of the leaf through these openings as well as water Vapour evaporating from the Leaf a process known as Transpiration the Spongy Mesophyll layer Contains arrangements of vascular tissue Consisting of xylem and phloem that are specialized for the transport of [water] and nutrients throughout the plant the Vascular tissue extends from the leaves through the stem to the roots Water is transported in xylem from the roots where the water potential is higher Up to the leaves [where] the water potential is lower The arrangement of the tissues the functions of the cells and water potential Determine the direction in which water will move through a plant water passes out of the leaf as water vapor through the stomata The water vapor lost from the leaves is replaced with water that enters through the roots and is brought up through the stem in Xylem Xylem is composed of vessels. Which are continuous tubes formed from Dead Hollow cylindrical cells arranged end to end and Tracheids which are dead cells that taper as the ends overlap? this arrangement and the polar Nature of water molecules Allow water to pass in an unbroken stream through the xylem from the roots up through the chute and into the leaves Adhesion is the attraction of water molecules to a surface such as the wall of the xylem Cohesion is hydrogen bonding between water molecules together adhesion and cohesion Allow water to move through the xylem in a continuous stream From the roots up through the stem to replace water lost from the leaves through the stomata Water enters the plant through the epidermal cells of the roots and travels into the xylem Water potential in the cells of the roots increases when symporter pumps in the plasma membrane Allow Protons to pass into the cell traveling down their concentration gradient These pumps couple the transport of protons with the transport of Minerals and other solutes into the cell water Follows into the cell driven [by] Osmosis the presence of Aquaporin channels in the Membrane Enhances Osmosis Allowing bulk flow of water from the soil into the roots The other main vascular tissue is Phloem Phloem Transports Carbohydrates and Amino acids that are produced in the leads to cells in the roots and stems where they are used and stored Conduction in Phloem is carried out through two kinds of elongated cells sieve cells and sieve Tube members most angiosperms contain Sieve Tube members Both types of cells have clusters of pores known as sieve areas that are abundant on the overlapping ends of cells these structures aid in the movement of carbohydrates like sucrose that are manufactured in the leaves and Carried in the Phloem throughout the plant a process called Translocation Turgor pressure Increases in the sieve Tube members as sucrose from surrounding cells is brought into phloem through active Transport water then enters Phloem from Xylem by Osmosis which drives the transport of carbohydrates in the Phloem? Water movement in vessels is one way while transport in Sieve Tube members can go in both directions Water potential is an important driver in both Xylem and Phloem transport but only phloem transport utilizes both active and passive Transport Our heart pumps blood throughout our bodies to provide nutrients and water to ourselves vascular Plants can accomplish this same feat without a heart using transpiration water potential and Translocation to move water nutrients and minerals to all cells of the plant

See also

External links

This page was last edited on 16 May 2020, at 22:12
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