3.1. Effect of explant and plant growth regulator types on the growth and shoot induction percentages of three Philodendron cultivars
Three months following the treatments, none of the explants grown on the PGR-free control medium showed any growth (Table 1). In contrary, explants grown on PGR-containing media presented different growth patterns depending on the type of explants cultured. With the lamina explants, growth was initiated by the enlargement of the explants followed by the production of small and round globules along the cuts across the mid-vein (Fig. 1a). These globular structures, however, were not able to develop further and convert into shoots. With the petiole explants, growth also manifested as small globular structures and occurred at the proximal ends of the petioles (Fig. 1b). Some of these protruding globules later developed into shoots, appearing either individually or in clusters. With the stem nodal explants, swelling of the nodes was followed by the emergence of dormant axillary buds. In some cases, adventitious buds were formed at the base of the developing axillary shoot to form a shoot cluster (Fig. 1c). Occasionally, roots were observed to develop from the node region.