Complex tissue is made up of more than one type of cells working together as a unit.
Following are kinds of Complex tissue:
(1) Xylem
Xylem or wood in conducting tissue and is composed of elements of different kinds (a) tracheids (b) vessels or tracheae (c) wood fibres and (d) wood parenchyma. Xylem as a whole is meant to conduct water and mineral salts upward from the root to the leaf and to give mechanical strength to the plant body. Except wood parenchyma all other xylem elements are lignified, thick walled and dead.
(a) Tracheids: These are elongated tube like dead cells with hard, thick and lignified walls and a large cell cavity. Their ends are commonly tapering or oblique. Their walls have one or two rows or bordered pits. Tracheids may be annular, spiral, scalarinform or pitted. Tracheids occur alone in the wood of ferms and gymneosperms where as in wood of angiosperms they occur associated with vessels. Tracheids give strength to plant body but their main function is conduction of water and muneria salts from root to leaf.
(2) Vessels or Trachea
Vessels are rows of elongated tube like dead cells placed end to end with their transverse of end walls dissolved. A vessel or trachea is like series of water pipes forming a pipe line. Their walls are thick and are named annular, spiral, scalarigorm, raticulate and pitted. Associated with vessels are often found some tracheids. Tracheids and vessels form main elements of wood or xylem of vascular bundle theory. They strengthen plant body.
(3) Wood Fibres
Scclerenchymatous cells associated with wood or xylem are known as wood fibres. They occur in woody dicotyledons and add to the mechanical strength of xylem and plant body.
(d) Wood Parenchyma: Parenchymatous cells associated with xylem together form wood parenchyma. The cells are alive, thin walled and abundant. It helps in conduction of water upward by vessels and tracheids. It also serves for food storage.
(2) Phloem:
Phloem or bast is another condition tissue and is composed of (a) Sieve tubes (b) companion cells (c) phloem parenchyma and (d) basi fibres (rarely). Phloem as a whole is meant to conduct prepared food material form leaf to the storage organs and the growing regions.
(a) Sieve Tubes: Sieve tubes and slender, tube like formed of elongated cells placed end to end. Their walls are thin made of cellulose perforated by a number of pores. It then looks very much like a sieve and is called sieve plate. Sieve tubes contain no nucleus but has living layer of cytoplasm which continuous through the spores. Sieve tubes carry prepared food material, soluble proteins and carbohydrates from storage organs to growing regions of plant body.
(b) Companion cells: Associated with each sieve tube and connected with it by simple pits there is a thin walled elongated cell known as companion cell. It is living containing protoplasm and a large elongated nucleus. It is present in angiosperms.
(c) Phloem parenchyma: These cells are present in the phloem. These are living and in shape often cylindrical. Phloem parenchyma is mostly absent in monocotyledons.
(d) Bast Fibres: Sclerenchymatous cells occurring in phloem or bast are known as bast fibres. These are absent in the primary phloem but are of frequent occurrence in secondary phloem.
(3) Secretary tissues:
(i) Laticiferous tissue: This consists of thin walled greatly elongated much branched ducts containing a milky juice the latex. These ducts are latex vessels and latex cells. They contain numerous niclei which lie in thin living layer of protoplasm. They lie irregularly distributed in the mass of parenchymatous cells function of these ducts is known fully known. They may act as fod storage organs or reservoirs of waste products. They act as translocatory tissues.
(ii) Latex vessels: They are rows of more or less parallel ducts connected with one another by the fusion of their branches forming a network.
Latex vessels are found in poppy family.
(iii) Latex cells: Latex cells are branched like latex vessels and are really single or independent units. They branch through parenchymatous tissue of the plant but without fusing together to form a network e.g.: Madar.
(iv) Globular tissue: This tissue is made of glands with secretary products.
.jpg)