Systematic implications of trichomes in the species of Stachytarpheta found in Awka, Nigeria

A trichome study was conducted on the various parts of Starchytarpheta species present in Awka South East Nigeria. Stachytarpheta is a plant of the family Verbenaceae, it is an erect and branched half-woody plant, with stem slightly angled. The study was carried out using standard plant anatomical methods by various authors with some modifications. The study revealed the presence or absence and distribution of trichomes on various parts of the plants including the adaxial and abaxial surfaces of the leaf, stem, petiole, midrib, calyx, veins and petal. On the other hand, the trichome density study of the epidermal surfaces revealed the various trichome densities on the epidermal surfaces of the three Stachytarpheta species. The highest trichome density was on the abaxial surface of S. angustifolia (12.00±8.485) and least trichome density was on the adaxial surface of S. jamaicensis (1.00±1.414). The indications from the species grouping as shown by the Duncan multiple Range Test shows there is no significant difference in the trichome density between Stachytarpheta species and between epidermal surfaces as they all bear the same alphabets in the superscript. More so, the mean trichome density on epidermal surface (figure 2) showed that mean trichome density was higher on the adaxial surface than on the abaxial surface; the high frequency of these trichomes on the adaxial surface of the three species can be related to protection against excessive radiation and higher temperature and even as protection against some form of predators. Trichome size (μm) was highest on the abaxial surface of S. cayannensis (501.3±119.9) and lowest on the abaxial surface of S. angustifolia (98.1±15.7); the analysis of variance shows a significant difference in the trichome size between Stachytarpheta species (p<0.05) but not between epidermal surface (p>0.05). The study however, reaffirms the taxonomic relationship that exists between these three Stachytarpheta species.

Author(s): Chisom F. Iroka, Clement U. Okeke and Chukwu N. Okereke

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