Desiccation Tolerance, Germination and Moisture Sorption Isotherm of Garcinia afzelii seeds

Abstract

The desiccation tolerance of Garcinia afzelii seeds was determined and sensitive vigour tests for assessing seed deterioration of this species were identified. Matured fruits were harvested in March 2009 from a small plantation at Ho in the Volta Region of Ghana. Depulped seeds were mixed with moistened sawdust and placed in white cotton sacks and quickly transported by air to the Seed Conversation Department of the Royal Botanic Gardens in the United Kingdom where a part of the experiment was carried out. The second season’s seeds was also harvested from the same plantation in April 2010 and used for another part of the studies in Ghana. Seed equilibrium relative humidity and moisture content on receipt in the United Kingdom were 93.3 % and 38.2 % respectively. Seed germination percentage decreased gradually with reduction in seed moisture content until after 25 % moisture content when germination percentage reduced drastically to 43 % at 23 % moisture content. The seeds of Garcinia afzelii are recalcitrant, with ‘critical moisture content’ about 25 %. Seedling dry weight, seed vigour index and speed of germination also decreased as seeds were dried. Electrical conductivity of leachate from seeds increased with desiccation of seeds. Water sorption isotherm curve for the species showed the typical sigmoid shape curve similar to that of orthodox species. Key words: Garcinia afzelii, vigour index, seedling dry weight, electrical conductivity, critical moisture content, moisture sorption isotherm.