PLANT TISSUES IOI 



PARENCHYMA 



Parenchyma or Fundamental Tissue is the soft tissue of plants, 

 consisting of cells about equal in length, breadth and thickness 

 (isodiametric) with thin cellulose cell walls enclosing protoplasm and 

 a nucleus and frequently substances of a non-protoplasmic nature. 

 There are four generally recognized types of parenchyma, viz.: 



Ordinary Parenchyma (Soft Ground Tissue, Fundamental Tis- 

 sue). Next to the meristem this is the least modified of all plant 

 tissues. It is generally composed of thin-walled cells, commonly 

 polyhedral or spheroidal in form and often of approxinately the 

 same length, breadth, and thickness (isodiametric), the cell walls are 

 composed of cellulose which is usually unmodified. Occasionally 

 the outline of the cells is star- shaped, as in the Wood Rush or Pick- 

 erel Weed or the cells may be several times as long as wide, as in 

 Pelargonium, etc. Moreover, markings may occur on the walls. 

 These may be of the nature of pores, as in the parenchyma cells of 

 the pith of the Elder or Sassafras, annular or reticulate thickenings, 

 as in the Mistletoe, or spiral thickenings, as in certain Orchids. 

 Protoplasm and a nucleus are always present, but in old cells are 

 only seen as a thin layer pushed up against the cell wall. Ordinary 

 Parenchyma may be seen composing the soft tissues of roots, stems, 

 and barks. 



Assimilation Parenchyma (Chlorophyll or Chromophyll Paren- 

 chyma, Chlorenchyma). This form of parenchyma tissue is found 

 in foliage leaves, floral leaves, in the outer region of young green 

 stems and fruits. Its cells are thin walled and vary in shape from 

 more or less isodiametric to irregular and elongated forms. The 

 cells always contain chloroplasts or plastids, in whose pores may be 

 found some other coloring substance. 



Conducting Parenchyma. This type of .parenchyma functions 

 in the rapid translocation of food materials to distant regions in .the 

 plant. It includes the wood parenchyma cells of the xylem which 

 convey a portion of the crude sap (water with mineral salts in 

 solution) and the phloem parenchyma (soft bast) which transports 

 the elaborated sap (carbohydrate and proteid material in solution). 

 Conducting parenchyma cells differ from those of ordinary paren- 



