Components Of The Stigmatic Exudate Of Raphia hookeri, Mann And Wendl

Abstract

Raphia hookeri, like all Raphia species, flowers once and dies. It is protogynous and the stigma secretes at anthesis a transluscent fluid (exudates) which hardens after three to four days. This fluid attracts insects and fruit set, though generally scanty on the species (0.1- 0.5%) is observed to be very poor in palms with heavy insect visitation during female flower anthesis. The stigmatic exudates were analyzed to determine its components with a view to understanding its role in pollination in the palm.The exudates oil was analyzed by the AOCS methods while the total sugar was determined by the methods of Whistler and Wolfrom. The fatty acid distribution was obtained on an APU model gas chromatography machine and the presence of phenolic compounds was determined by scanning alcoholic extracts of the exudates with and without sodium hydroxide.The fluid (exudates) was found to contain 0.28% oil, 0.8% sugar and four main fatty acids and traces of two others with intermediate chain lengths (10 – 18). The lipid components of the exudates ensures that the stigmatic surface is protected from desiccation to enable it trap pollen while the 0.8% sugar possibly serves as a source of energy for initial pollen germination on the stigma. Phenolic compounds present probably act as insect repellant and also inhibit spore germination to keep the exudates in good condition during the three to four days of female anthesis.

Keywords: Raphia hookeri, stigmatic exudate, palmitic acid

Journal of Agriculture, Forestry and the Social Sciences Vol. 4 (2) 2006: pp. 83-88