TOMLINSON1, P. BARRY*, RUSSELL E. SPANGLER1, AND GORD LEMON2. (1) Harvard Forest, Harvard University, P. O. Box 68, Petersham, MA 01366, (2) Department of Botany, University of Toronto, Toronto, ON M5S 3B2, Canada. - Development of the shoot vascular system in the rattan palm Calamus.
Calamus is a genus of 360 species of climbing palms, the stems
of which supply commercial rattan cones. Shoots are supported by
flagella, which are sterile, unbranched inflorescences adnate to
internode and leaf sheath above their morphological level of
insertion. The mature stem vascular system is unusual in that axial
bundles do not interconnect directly and end blindly below when
followed in a basipetal direction. At most, there are obscure and
irregular transverse commissures that connect peripheral bundles
indirectly. These develop from late differentiating procambial
strands by dedifferentiation of partly mature ground tissue cells.
Protoxylem and metaxylem differentiate well separated from each other
within any axial strand so that there is no protoxylem-metaxylem
connection at maturity. Axial bundles differentiate over long
distances independent of the leaf they will ultimately supply.
Protophloem differentiates as a single strand, but becomes separated
into two adult strands as it is replaced by fibers and lateral
metaphloem. These features are undoubtedly a consequence of the
extensive intercalary growth of all organs, but it is a mystery how
the mature vascular system can function in long distance transport
despite the lack of interconnection.
Key words: Calamus,development,palm,rattan,vascular system