Effect of Plant Leaf Positions on Some Micronutrients, Anti-nutrients and Toxic Substances in Telfairia occidentalis at the Vegetative Phase

Pot experiment was conducted to determine the effect of leaf positions on the concentrations of some phytotoxins (cyanide, nitrate, soluble and total oxalates), micronutrients namely; vitamin C, β-carotene (provitamin A) and mineral elements (Fe, Mg, Cu, Zn, Ca Na and K) at vegetative phase of Telfairia occidentalis grown in nitrogen and non – nitrogen treated soil. The leaves of Telfairia occidentalis were harvested and analysed at three different leaf locations, namely; basal, middle and upper positions. The result obtained showed that no significant differences was observed in the cyanide concentration between basal and middle leaves and between middle and upper leaves, however, basal leaves had significant (p< 0.05) higher concentration of cyanide than upper leaves irrespective of soil nitrogen levels. The concentrations of nitrate and β-carotene in control and nitrogen fertilized Telfairia occidentalis were significantly (p<0.05) highest in upper, followed by middle and lowest in the basal leaf position. The soluble and total oxalates content in Telfairia occidentalis were significantly (p<0.05) higher in the basal and middle leaves than the upper leaves irrespective of soil nitrogen levels. While the vitamin C concentration in the vegetable was significantly elevated in basal leaves than the leaves obtain from middle and upper leaf locations. Analysis of mineral elements showed that Fe, Mg, Zn and Ca were concentrated more in the basal and middle leaves than the upper leaves while the K concentration was signififcantly (p<0.05) higher in the middle and upper leaves than the basal leaves in control and nitrogen treated Telfairia occidentalis. The results conclude that concentrations of most of the plant toxins are higher in the older leaves than younger ones. Thus inclusion of the younger leaves of Telfairia occindentalis in our meal will reduce the negative health effect associated with high ingestion of the phytotoxins.