TAXONOMY AND NUTRIENT COMPOSITION OF SPECIES IN THE Vernonia hymenolepis A. RICH. COMPLEX IN TROPICAL EAST AFRICA

Abstract

Three Stengelioid species forming a complex in the genus Vernonia Schreber. in Tropical East Africa viz., Vernonia calvoana (Hook.f.) Hook.f., Vernonia hymenolepis A. Rich. and Vernonia tolypophora Mattf. were investigated to establish their taxonomic relationships. Specimens were collected from various parts of Kenya and herbarium specimens sourced from the Royal Botanic Garden (Kew) and Missouri Botanical Gardens (MO) in addition to those deposited at the East African herbarium (EA) for the three East African countries. Leaf and floral characters obtained from 123 herbarium specimens covering almost the entire range of the complex were examined. Measurements were made of each quantitative character per specimen using a hand ruler or under a WILD M3 dissecting microscope. Qualitative characters were scored as binary characters. The data obtained was used to determine their relationships by subjecting it to multivariate analysis. In the Principal Component Analysis (PCA) the three species almost formed one coherent group while the Cluster Analysis (CA) produced no clear cluster of any of the species. Discriminant Analysis (DA) similarly did not clearly discriminate between them. Univariate analyses (UA) did not reveal any character among those investigated that is able to separate the species. The results showed that the three species overlap in many leaf and floral characters. However Independent t-test showed significant levels of statistical difference between the species in respect to some of the characters. There were also subtle differences in the inflorescence morphology of V. hymenolepis and V. tolypophora and achene pubescence of V. hymenolepis and V. calvoana. The results suggest that the three entities are largely indistinct and are therefore likely part of a morphologically variable species. It is therefore proposed that V. calvoana and V. tolypophora should be synonymized under the earliest name V. hymenolepis. Following this, there is need to make new combinations of the subspecies recognized under the synonymized V. calvoana. Nutrient composition of the the leaves of Vernonia hymenolepis was determined using atomic absorption spectrophotometer and flame photometer for mineral elements, Kjeldahl method for Nitrogen and titration using iodine and 1% starch solution for Vitamin C. The Nutritional data revealed a high quantity of nutritive elements. The leaves had a Vitamin C mean content of 1120.4mg/100g (SD 274.5) and 303.2mg (SD 191.0), 1207.5mg (SD 1262.5) and 133.8mg/100g (SD 153.3) dry weight (d.w) of Sodium, Iron and Zinc respectively. Protein levels in the leaves ranged from 11.2-18.1g/100g d.w.There is therefore need to explore possibilities of domesticating V. hymenolepis to be used as a vegetable.