PLANT TISSUES 



PLANT TISSUES 



A tissue is an aggregation of cells of common source, structure 

 and function in intimate union. 



According to structure the following tissues are found in various 

 forms of higher plants: 



1. Meristem 8. Laticieerous tissue 



2. Pasenchyme 9. Cribieorm or sieve tissue 



3. Collenchyme 10. Woody fibre tissue 



4. SCLERENCHYME II. HaRD BAST 



5. Epidermis 12. Tracheary tissue 



6. Endodermis 13. Medullary rays 



7. Cork 



A mass of tissue so united in the plant as to constitute a distinct 

 unit is called a tissue system. Three systems of tissues are commonly 

 distinguished in higher forms of plants: 



The epidermal or tegumentary system 

 The fundamental system 

 The pibrovascular system 



Meristem, frequently called embryonic tissue, is undifferentiated 

 tissue composed of cells in the state of rapid division. 



Parenchyme or Fundamental Tissue is the soft ground tissue of 

 plants consisting of cells about equal in length, breadth and thickness 

 (isodiametric) with thin cellulose cell walls enclosing protoplasm and 

 a nucleus. Three important kinds of parenchyme, viz. : Chlorophyll 

 parenchyme, containing chloroplasts and found in green parts of plants; 

 reserve parenchyme occurring in seeds, and underground parts of 

 plants and containing starch, aleurone grains, fixed oils, etc. ; conducting 

 parenchyme found distributed in various parts of plants and serving for 

 the transferral of food. 



Collenchyme consists of elongated prismatic cells whose walls are 

 of cellulose. The angles of the ceUs are thickened with a colloidal 

 substance. It is found beneath the epidermis of many plants, rarely 

 alongside the endodermis and forms the "ribs" of stems such as in 

 Burdock, Caraway, etc. Its function is that of support. 



Sclerenchyme or "stony tissue" is made up of stone cells variously 

 shaped. These were formerly parenchyme cells whose walls became 



