MORPHOLOGICAL CHARACTERISTICS AND PROPAGATION OF HELICIA COCHINCHINENSIS LOUR. (PROTEACEAE): A NATIVE SHRUB OF THE NORTHERN HEMISPHERE

Abstract

The micromorphological characteristics of leaves, flowers, and seeds were observed for Helicia cochinchinensis, which is the only member of the Proteaceae family to be represented in Japan. Leaf surface was found to be hypostomatic with a rough cuticular topography lacking pubescences. The abaxial leaf surface always presented numerous stomata with a particular tendency for stomatal density to be higher towards the tip portion of the leaf. An enlarged stomatal view showed numerous stomata spread in a radial disposition (actinocytic), and their guard cells were surrounded by a structure with a circular form. Flowers were composed of four tepal segments positioned in a linear manner which, during anthesis, break and curl backwards until they touched the style base. The long and slender stamens were adnate to the corolla through a short filament, and retained numerous pollen grains of a triangular form. The lower part of the pistil consisted of a superior ovary surrounded by ovate hypogynous glands, and longitudinal ridges were detected at the upper stylar part at the stigmatic surfaces. Stomata were also present in both the anther abaxial surface and in the perianth. In addition, the perianth adaxial surface showed only a few stomata having varied morphological features. These findings confirm the presence of some anatomical traits common among its species. Fruits and seeds differed significantly in length, diameter and weight and these characteristics appeared to be related to the original harvest sites. The embryo was undifferentiated as the plumule and radicle could not be recognized. The seeds germinated two months after sowing at 25°C and one month later at 20°C. The requirement for low temperature is not considered a determinant for seed germination. For cutting propagation, the application of auxin Oxiberon (1% IBA) in a talc treatment gave a high rooting rate and increased the number of roots per cutting in comparison to IBA applied as dipping treatment at 150 ppm.