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Parenchyma Cells and Tissues
This image of parenchyma cells was used earlier to emphasize
vacuoles. The term "parenchyma" was also introduced in the plastid
unit. Keep in mind parenchyma cells possess thin primary cell walls. Large
vacuoles can make these cells appear empty when stained but they are hardly
non-functional in the living plant tissues. Note the abundant intercellular
spaces that are typically present. These are sites of apoplastic transport.
Parenchyma are the most abundant cell type. You should expect
to find these in all plant parts. In leaves and stems parenchyma are the only
photosynthetic cells. When filled with chloroplasts, they are called chlorenchyma.
Parenchyma cells are better suited for photosynthetic activity because their
thin primary cell walls allow more efficient passage of light, water, gases,
and metabolites. Remember, as walls of cells become thicker, transport processes
You might also recall parenchyma are the only cells that can
engage in mitotic divisions. Subsequently, they are the only type of cell
found in apical meristems. Some of these are shown in various stages of division
in the mitosis unit.
In roots or stems parenchyma cells can be found as storage
cells filled with starch. Some of these were shown in the plastid module.
Watch for these in the Ranunculus root microscopy unit!
Specialized parenchyma is found in aquatic plants that require
flotation for their leaves. The open, air-filled parenchyma tissue in these
leaves is called aerenchyma.
Roll your mouse over the triangular intercellular
space next to the round nucleus.