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Author : ass.-prof. Shanayda M.I.

Lecture 3 VASCULAR AND MECHANICAL TISSUES OF PLANTS. VASCULAR BUNDLES. Author : ass.-prof. Shanayda M.I. At the last lecture were stadied different t y pes of plant tissue s – the meristem, dermal, secretory and ground. At present we are study ing the VASCULAR

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Author : ass.-prof. Shanayda M.I.

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  1. Lecture 3 VASCULAR AND MECHANICAL TISSUES OF PLANTS. VASCULAR BUNDLES Author: ass.-prof. Shanayda M.I.

  2. At the last lecture were stadied different types of plant tissues – the meristem, dermal, secretory and ground. At present we are studying the VASCULAR and MECHANICAL tissues of plants. VASCULAR and MECHANICAL tissues of plants contain 90 % of wood in trees

  3. MECHANICAL TISSUES The tissues that support plant are called mechanical tissues.They belong to simple tissues, because include only one type of cells. There are two types of mechanical tissues: collenchyma and sclerenchyma.

  4. Collenchyma tissues are mainly found under the epidermis in young stems and in the large veins of leaves. The cells are composed of living, elongated cells running parallel to the length of organs that it is found in. Collenchyma cells have thick cellulose cell walls which thickened at the corners or at two opposite sides. The cells sometimes contain chloroplasts.

  5. Types of collenchyma are classified according to the arrangement of the wall thickenings and include: angular collenchyma: cell wall is thickest in the corners. lamellar collenchyma: cell wall is thickest on two opposite sides. lacunar collenchyma: cell wall is thickest in the corners, intercellular air (in water plants)

  6. Sclerenchyma tissueshave the rigid cells and thick secondary cell walls with lignin. They support and strengthen nonextending regions of plants such as mature stems, and are usually dead at maturity.Sclerenchyma also makes up the hard outer covering of seeds and nuts. Types of sclerenchymaare classified according to cell shape and include: fibers and sclereids 1) fibers are long, straight and thin, often occurring in bundles. Usually fiber cells are much longer than they are wide and have a very tiny cavity in the center of the cell.

  7. 2) Sclereidsarevariable in shape, but not like fibers. Types are classified according to shape and include the following: brachysclereids:also called stone cells, length and width nearly equal.astrosclereids:star shaped, with several projecting arms.trichosclereids:hair-like, similar to a fibers, except branched.osteosclereids:bone shaped, elongated with swollen ends. macrosclereids: column shaped

  8. Groups of brachysclereids (3,4) in cross section of the bark of oak-tree

  9. The VASCULAR TISSUES The VASCULAR TISSUESare specialized for long-distance. Xylem and phloem are two the most important complex tissues in a plant, as their primary functions include the transport of water, dissolved minerals and soluble food substances (photosynthate) throughout the plant.

  10. The vascular tissues are complex (composed of several cell types). XYLEMconducts water and dissolved minerals from the roots to all the other parts of the plant. So xylem is the water-conducting tissue of plants. Xylem is a complex tissue composed of xylem vessels (or tracheids), fibers and parenchyma cells:

  11. Vessel elements are the long tube with perforation plates. Xylem vesselsof Angiosperm are deposited in spirals and rings and are usually perforated by pits. Tracheidsare the tracheary elements that lack perforations plates Tracheids are tapered at the ends. The xylem of Conifers contains only tracheids.

  12. 2) Libriform fibersare the cells of mechanical tissue in the xylem. They are very long and dead. Their functions are to serve as supporting and strengthening elements of xylem. 3) Xylem parenchyma cells are alive and have thin wall. They distinct the intercellular spaces. SUMMARY …

  13. PHLOEM is the photosynthate-conducting tissue of plants. Phloem is a complex tissue composed of sieve elements, companion cells, fiber elements and parenchyma cells. The main components of phloem are sieve elements and companion cells.

  14. Sieve elementsare the • conducting cells in the phloem. • They are with perforation plates • and without secondary wall. • Sieve elements have no nucleus and • depend on the adjacent companion cells • for many functions. • Companion cells are cells • in the phloem that is connected • to a sieve-tube member by • numerous plasmodesmata. • They have a nucleus. • The phloem of Conifers • has no companion cells. • SUMMARY …

  15. The VASCULAR BUNDLES The xylem and phloem are the two most important complex tissues in a plant and situated in organs of plants togetheras vascular bundles. Sometimes they contain a vascular cambium (the lateral meristem).

  16. The VASCULAR BUNDLES are classified according to special relationships of xylem and phloem. There are several types of vascular bundles. All these types are typical for some divisions, classes, families and plant organs:

  17. Collateral bundles have xylem on one side and phloem on the other side. There are close and open collateral bundles: opened collateral vascular bundle (with cambium) formed in stems of Dicotyledon plants (1); • closed collateral vascular bundle (without cambium) formed in stems and leaves of Monocotyledon plants (3); • Bicollateral bundles have phloem on both sides of the xylem; they also have cambium (formed in stems of pumpkin (2),

  18. Concentric bundles are common only for rhizomes • (underground shoot modifications). They are divide to: • Centerphloem amphivasal – if xylem surrounds • the phloem (in Monocots – (4),Centerxylem amphicribral – if phloem surrounds • the xylem (in Ferns – (5)

  19. Radial bundles have xylem occurs in radial directions, and phloem takes place between them (in young roots). Radial polyarch vascular bundle is typical only for roots of Monocot plants. Dicot have radial tetraarch or tryarch vascular bundle.

  20. GLOSSARY OF TISSUES OF THE PLANT BODY

  21. 1.MERISTEMS produce all types of tissues. There are general zone in which cell division is frequent. 2.DERMAL TISSUES SYSTEM are tissues that cover the surface of the plant body.. 3.GROUND TISSUES SYSTEM are simple tissues composed of alive cell. They can accumulate of storage products and photosynsate. 4.SECRETORY STRUCTURES produce different solutions, can be of outer and inner forms. 5.MECHANICAL TISSUES support the plant body. 6.VASCULAR TISSUES conduct different solutions.

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