Mature plants of Ferocactus latispinus were divided into the apical meristem, cortical and cambial tissue, and young and mature photosynthetic tissue. Pieces 2x2x4 mm were fixed in 0.075 M PIPES buffered 5% glutaraldehyde and further treated for conventional transmission electron microscopy.The shoot meristematic cells contained dense cytoplasm with a few small vacuoles. All organelles expected to be found in unspecialized plant cells were present. The proplastids were 1-2 diameters larger than mitochondria. Some of these plastids were elongated and most contained small amounts of lipid globules in the stroma (Fig. 1). In addition, phytoferritin was sometimes found in the stroma. No starch was found in these organelles. The thylakoids were poorly developed, and when there were no inclusions in the stroma, proplastids were difficult to distinguish from mitochondria (Fig. 1).Cortical cells had very large, well-developed vacuoles. The organelles were restricted to the peripheral cytoplasm of the cell and to a few transvacuolar cytoplasmic strands.
Freeze-substitution transmission electron microscopy of gentian shoot tips cryopreserved at ultra low temperatures