Pelargonium stem, TS
stem shown here is another example of
a dicotyledonous plant that undergoes only limited secondary growth.
In Pelargonium, the cortex remains separated from the stele by a starch
sheath (SS) -- shown between the two dotted lines . The phloem can be
seen underneath this layer, and underneath this, (endarch to)
are zones of primary phloem fibres (PPF). Some secondary xylem (2X) has been formed from the
cambium (CZ). Note the position of the first-formed xylem elements,
called the protoxylem, (PX) right
on the inner margin of the vascular tissue.
The inner region of this stem contains a simple pith of parenchyma cells, which contain starch within numerous amyloplasts.