Re: Why can plant cells afford to be larger than animal cells?

Consider the major differences between plant and animal cells. Plant cells have
cell walls, which provide support and perhaps enable plant cells to be larger.
Plant cells usually have large vacuoles, so the amount of cytoplasm per cell may
be more similar between plant and animal cells. 

The diffusion limitation you mentioned is not as bad as it may seem because the
metabolically active part of the plant cell is mainly the thin layer of
cytoplasm near the cell wall. The vacuole has important functions but largely
stores potentially toxic substances and provides turgor for the cell.  

Plants grow by expanding their cells so it requires less costly building
materials more to have fewer cells that reach a larger final volume than more
numerous, but smaller cells.

References


Martya, F. 1999. Plant vacuoles. Plant Cell 11: 587-600.


Re: what good is a vacuole?