COMMON CELL AND TISSUE TYPES

Raven 7th p. 510-527; 8th p. 538-557,

The plants you will study in Biology 210 are all vascular plants, that is, plants with cells and tissues modified for the transport of water, inorganic nutrients and organic materials. To fully appreciate the variation and complexity of tissues found in vascular plants, we begin by studying the basic cell types and tissues in angiosperms (flowering plants) and some conifers. In the second part of the term, we will study the major groups of vascular plants using fresh material, prepared slides, and demonstration material.

Multicellular plants consist of cells organized and grouped into tissues which in turn are organized into organs. In plants, the boundaries between cell type, tissue and organ are blurred, so it is important that you distinguish clearly between cell type and tissue type. You will find that different cell types intergrade, and that a particular cell may even change from one type to another during the course of its life. Hence, tissues formed from such cells also intergrade. In this part of the course you will examine the three generally recognized tissue systems: GROUND TISSUE SYSTEM, VASCULAR TISSUE SYSTEM and DERMAL TISSUE SYSTEM. Another way to define plant tissues is if they contain cells of only one type (simple), or are complex, containing a number of different cell types. It is important to remember that a tissue is defined by its function, e.g. xylem is the water-conducting tissue of a plant.

The various cell types found in plants all differentiate from parenchyma cells. The final structure of a given cell is determined by a complex number of factors including its position in the plant and the physical stimuli to which it is exposed. Once highly specialized for one or more functions, a cell cannot normally revert to the original cell type. The sequence from a simple parenchyma cell to a highly specialized one can often be seen by examining sequentially older cells within a given plant structure.

GROUND TISSUE SYSTEM
VASCULAR TISSUE SYSTEM
DERMAL TISSUE SYSTEM