A cross section of a young rice root that is stained with toluidine blue.  Notice the solid cortex.  The radiating pattern of the cortical parenchyma cells is unique to the younger stage of a rice plant.  Since this root is so young, it is hard to identity the endodermis, which separates the vascular cyclinder from the cortex.    

This is a cross section of an older rice root.  Notice that the cortical parenchyma cells are beginning to develop lacunae (air space between cells).  The cortical fibers are made up off sclerenchymatous cells.  The cortex is surrounded by two protective layers: the sclerenchymatous layer and the exodermis.
 
 
 
 

This is a close-up picture of the exodermis and the sclerenchymatous layer.  The exodermal cells flatten as the root matures.  Others studies done on rice roots indicate that the exodermis becomes the functional epidermis when the epidermis is sloughed off.  The layer that is exterior to the exodermis is the epidermis, which is discussed in the dermal tissue system.

 
 
 

This is a cross section of a mature rice root that is stained with toluidine blue.  At this satge in development, the cortical parenchyma cells have lost their cytoplasm, thus resulting in large intercellular spaces.  The exodermal cells are becoming suberized.  The sclerenchymatous cells seem to have no cytoplasm.

 
      This is a cross section of mature rice root.  Although the radiating pattern of the cortical parenchyma cells is still visible, many of the cortical cells have collapsed, pulling away from adjoining radial walls.  Studies suggest that the cortical fiber assists in preventing the collapse of extensive cortical aerenchyma cells.  
 

Introduction | Flowers&Fruit | Roots | Stems | Leaves

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© Thomas L. Rost 1997 Section of Plant Biology Division of Biological Sciences UNIVERSITY OF CALIFORNIA, DAVIS