ABSTRACT

The study investigated the growth characteristics and chemical composition of Gnetum africanum and G. bulcholzianum in different ecosystems in Nigeria lowland rainforest. The experiment consists of a 4x2 factorial experiment in RCBD for measurement of growth rate in rubber plantation and a 2x2 factorial experiment in RCBD for laboratory analysis. The results were expressed as mean standard Deviation and Standard Error. Duncan multiple range test was adopted to separate means and test for significant differences among means at (P>0.05). There was a significant difference (P>0.05) in growth rate of G. africanum and G. bulcholzianum but no significant difference in their girths. Gnetum as a shade loving plants experienced absolute shade in both environments. Dry matter and carbohydrate were higher in G. africanum (RF) 93.20±0.011% and G. bulcholzianum (rubber plantation) 93.16±0.075%. Least mean proximate compositions was found to be in G. bulcholzianum (RB) 1.77±0.125%, phenol was the least phytochemical with no significant difference (P>0.05) Alkaloid showed significant difference (P>0.05) with highest mean value of phytochemical composition and was higher in G. bulcholzianum 5.60±0.112mg/100g (RF) and G. africanum 4.75±0.050mg/100g (RB) than G. africanum of RF 3.83±0.887mg/100gm and RB 3.40±0.011mg/100g. Chromium and cadmium were significantly different with least mean values of heavy metal compositions. Chromium had values ranging from 0.08±0.003mg/100g in Gnetum africanum (RF) to 0.11±0.011mg/100gm G. bulcholzianum (RB), also cadmium had mean values of 0.24±0.152mg/100gm Gnetum africanum (RF) to 0.44±0.017mg/100gm G. bulcholzianum, (RF) which shows that gnetum is less toxic to human health. The two species of gnetum showed high significant amount of vitamin c component and least mean values of Vitamin B2 ranging from 0.56±0.011mg/100gm in Gnetum africanum (RB) to 0.63±0.011mg/100gm G. africanum (RB), it was higher in G. africanum 42.98±0.376mg/100gm (RB). Exchangeable cations needed for plant growth was significantly higher (P>0.05) in RB compared to RF. Na+ was the most limiting exchangeable cations in both top soils of rubber plantation and relic forest with values 0.13cmol/kg and 0.144cmol/kg respectively. Soil pH above 4.00 in both RF and RB shows favorable acidic nature for gnetum growth. Fe, Mn and S showed high significant difference and mean values in sub soils of RF than in RB. Gnetum species leaves have high nutritional value, phytochemical contents and medicinal values and it is recommended as cheap sources of plant proteins, materials for the synthesis of new drugs in pharmaceutical industries.