LATICIFERS Introduction, Structure, Classification and Functions

                            LATICIFERs

INTRODUCTION :-

• Laticifer is a general term applied to a large and heterogenous group of cells that responsible for latex production.
• Found in over 900 genera of plants, laticifers typically function as internal secretory systems.
• 900 genera distributed in 20 families of mostly in dicotyledons and  a few families of monocotyledons
•   Laticifers are highly specialized cells with unique DNA which can produce a wide variety of proteins.
• These proteins include enzymes functioning as proteinases and chitinases which help defend the producing plant against insects and other herbivores

 Defination :-

•       A laticifer is a type of elongated secretory cell found in the leaves or stems of plants that produce latex and rubber as secondary metabolites.
•      The word laticifer and its adjectival form laticiferous are derived from the word latex, meaning juice in Latin.

Latex :-

•     Latex is fluid produced in the latex vessels or cells. It is usually white and milky.
•     Latex is a mixture of many distinct compounds, there is always a predominance of terpenoids in its composition
•      Rubber tree has up to 45% polyisoprenes (rubber) in its latex composition .
•      In addition, fatty acids, phytosterols, alkaloids, phenolic compounds, proteins, cardenolides, starch grains, among other compounds, have already been identified in the latex of many species 

TYPES :-

 Laticifers divided into two type

1- Articulated laticifers

    Composed of a series of cells joined together. Fig (B).

2-Non articulated

It is a very long tube-shaped cell with many nuclei. Fig (A).

Articulated laticifers :-

•       A structure made up of many cells.
•       The laticifers run parallel to the vascular bundles, but just below them.And they are  branched.
•       Laticifers grow through the intercellular spaces and the enzyme pectinase helps in the process.

Non-Articulated :-

•      It is a very long tube-shaped cell with many nuclei .
•      Its walls are scalloped where the surrounding parenchyma cells press slightly into it.
•      The former is derived from the enlargement of a single cell.
•       This cell has the potentiality of unlimited and rapid growth, and elongates to form long latex tubes.
•       The tubes may remain unbranched termed non-articulate unbranched laticifer (e.g. Vinca, Cannabis, Urtica etc.)

Structure of  Laticifers :-

•      Laticifers in some plants contain numerous small vacuoles, or vesicles, which later merge with the central vacuole.
•      Osmiophilic globules are formed in the small vacuoles and later released into the central one.
•      Partial disintegration of protoplasts takes place in the central vacuole, apparently by autophagy.
•       The globules are retained.
•      The laticifers are long thin-walled cells.
•      Many show single perforations in the end walls.

Cell wall :-

•      The cell wall of laticifers is thick and may be thicker than the adjacent cells.
•      They are not lignified.
•      The growth of cell wall occurs through apposition process.
•      The tip of latex cell is thin walled.
•      The walls are composed of cellulose, hemicellulose and pectin.

Function :-

•         It is a vital sap vessel and similar to the blood vessels of animals.
•        It takes part in translocation of assimilates as it is associated with phloem.
•       It stores food materials.
•      It is now considered as secretory tissues where the secretory substances do not re-enter the   plant metabolism.
•      Sen and Chawan (1972) suggested that laticifiers regulate the water balance in plants.
•      It has role in the transport of oxygen.
•      It has role in healing up of wounds.
•      It acts as a defense against herbivores and microorganisms. McCay and  
•      Mahlberg (1973) reported the absence of bacterial activity from laticifers.