Indigenous knowledge of fever tea (lippia javanica) and effect of shade netting on plant growth, oil yield and compound composition

Abstract

An experiment was conducted to determine the effects of shade netting on growth, oil yield and compound composition of fever tea (Lippia javaica). The treatments were nine shade nets of different light intensities (100% bird net, 40% green, 10, 12 and 18% white and 30, 40, 55 and 70% black). The layout used was a completely randomized design. The parameters measured were shoot width, fresh shoot mass, the number of plants flowered, plant height and photosynthetically active radiation. Shade netting did not have any effect on the shoot width of L. javanica. Eighteen percent white net was best suited to produce fresh shoot mass, whereas 55% black net, 40% black net and 10% white net produced lower fresh shoot mass. More plants that flowered were obtained under 70% black net than those grown under 30% black net. The number of plants that flowered increased from 22 to 35 with an increase in shading density. The height of plants was not affected by shade netting at 49 DAT. However, at 59 and 67 DAT, the height of the plants was greater under low light intensities (40, 55, and 70% black nets) than that of high light intensity (30% black). Twelve percent white net had the greatest plant height at 102 DAT. Shade netting significantly affected the adsorption and utilization of photosynthetically active radiation (PAR) above, across and below the plants at 102 DAT. Hundred percent bird net had the greatest amount of light intercepted above, across and below the plants. The amount of light intercepted above, below and across the plants was lower for lower shading intensity (30% black) than that of higher shading intensities (40%, 55% and 70% black). To determine shade-netting effect on oil yield and compound composition, fresh leaves (± 200g) of L. javanica were sampled from each shade net for essential oil extraction by hydrodistillation. The oil yield ranged from 0.29% to 0.41%. The oil had a clear to yellowish brown colour. No significant differences were detected for oil yield amongst the shade nets. The chemical compound analysis was carried out by GC/MS. The chemical compounds identified in the essential oil were <font face="symbol">a</font>-pinene, sebinen, myrcene, 1.8 myrcene, ipsenone, ipsedienone, <font face="symbol">b</font>-caryophyllen and germacrene-D. L. javanica plants grown under 10% white net, resulted in significantly higher myrcene content (15.7%) as compared to plants grown in other shade nets. Shade netting did not have any effect on the composition of á-pinene, sebinene, 1.8 myrcene, ipsenone, ipsedienone, <font face="symbol">b</font>-caryophyllen and germacrene-D. For commercial usage of myrcene, white net (10%) would be best suited for L. javanica production. To obtain information about indigenous knowledge of L. javanica, a survey was carried out among street traders, traditional healers, hawkers and farmers in Gauteng. The age group was between 20 and 73. The majority of respondents, who were self employed, were traditional healers followed by farmers. Most (98%) of the respondents indicated that they collected L. javanica from the veld by cutting the plant, whereas other respondents uprooted the whole plant when harvesting. Amongst the different uses of L. javanica mentioned, treatment of colds and coughs through steaming was stated by most (47%) of the respondents. Most (88%) of the respondents felt that it was important to conserve the plant for future generations and also to prevent the plant from becoming extinct. Traditional healers knew the uses and other important aspects of L. javanica than the farmers.