The differentiation of phloem in plant tissue cultures offers a unique
opportunity to study the development and structure of sieve elements in a
manner that avoids the injury responses associated with the processing of
similar elements in intact plants. Short segments of sieve elements formed
in tissue cultures can be fixed intact while the longer strands occuring in
whole plants must be cut into shorter lengths before processing. While iyuch
controversy surrounds the question of phloem function in tissue cultures ,
sieve elements formed in these cultured cells are structurally similar to
those of Intact plants. We are particullarly Interested In the structure of
the plasma membrane and the peripheral ER in these cells because of their
possible role in the energy-dependent active transport of sucrose into the
sieve elements.
Osmotic Shrinkage as a Factor in Freezing Injury in Plant Tissue Cultures