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African rosewood (Pterocarpus erinaceus) is an endemic, highly exploited and endangered tree species in arid and semi-arid zones of West Africa. Identifying optimum conditions for seed propagation and storage is critical for its conservation. This study assessed the effects of four pretreatments on seed germination and seedling vigour. Varying temperature, duration and packaging on storage deterioration were also evaluated for 12-months. Moisture sorption isotherms at 20, 25 and 30°C were characterized by equilibrating seed samples on series of lithium chloride (LiCl) solutions, generating relative humidity (RH) range of 3-95%. Data were fitted to four mathematical models; Chung Pfost, Halsey, Henderson and Oswin to determine the most suitable for describing the water activity (a w ), equilibrium moisture content (EMC) and temperature relationship. Results indicate that whole fruit sowing reduced germination capacity by more than 50% compared with extracted seeds at 5% probability level. Seeds stored at -10°C recorded the lowest rate of seed deterioration compared with ambient storage, regardless of packaging. Moisture sorption isotherms for rosewood showed a sigmoid (S-shaped) profile characteristic of orthodox seeds, and best described by the Henderson equation. Our findings highlight the need for adopting improved seed extraction technology and orthodox seed storage protocols for P. erinaceus conservation.

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The relationship between storage temperature, relative humidity and seed water content was investigated for six indigenous forest tree seed species, namely Garcinia kola, Terminalia superba, Terminalia ivorensis, Mansonia altissima, Entandrophragma angolense and Khaya anthotheca in Ghana. Seeds were equilibrated over a series of lithium chloride solutions with relative humidities ranging from 12 to 93% and silica gel with relative humidity of 3% at 20 ºC. Seeds reached equilibrium with different days depending on seed size and structure, ranging from 13 days for E. angolense to 91 days for G. kola. When seeds equilibrated, moisture contents were determined gravimetrically, and values of moisture contents were then plotted against relative humidity to construct moisture sorption isotherms for the species. Seeds of T. superba, T. ivorensis, M. altissima, E. angolense and K. anthotheca, exhibited a sigmoidal relationship between seed water content and relative humidity indicative of three regions of water binding. Contrarily to other reports, the shape of the isotherm curve for G. kola -a desiccation sensitive species -also showed the reversed sigmoid pattern similar to isotherm curves of orthodox species rather than the monotonic shape. The isotherms showed that seed moisture content increased with increasing relative humidity. Seed samples of G. kola, placed at all relative humidities chambers, lost water(desorption) as the initial water content of 58% was very high and, therefore, possessed a higher water potential than the environments. Seeds of the other species either lost water (desorption) to the relative humidity chambers, or absorbed water from the chambers depending on the relative humidity of the environment they were placed.