Germination responses of Cola acuminata (Pal. De Beauv.) seeds to different substrates, photoperiods and dehydration

Abstract

Cola acuminata (Pal. De Beauv.), one of the many forest tree species which are of socio-economic importance in Western and Central Africa, is still exploited in the wild by subsistence farmers because it has not been domesticated yet. As a contribution to its domestication, the present study aimed at determining germination requirements and desiccation tolerance of seeds. Three substrates (forest topsoil, river sand and mixture of forest top soil and river sand), two photoperiods (12 hours/day and continuous darkness) and dehydration were investigated for their effects on seeds germination percentage. To evaluate the seeds’ tolerance to desiccation, fresh seeds were dried at laboratory temperature for 16 days during which seeds moisture content, seeds germination percentage and electrical conductivity of seeds leachate were monitored at two-day intervals. Results showed that the mean germination percentage recorded on the mixture of forest top soil and river sand (97.2 ± 1.0%) was significantly higher than that recorded on forest topsoil (85.5 ± 4.0%), which was in turn higher than that obtained on river sand (70 ± 1.5%). The effect of photoperiod on germination percentage was not significant (p = 0.112). As response to seeds drying, the mean germination percentage slightly decreased as moisture got lost, then drastically dropped when moisture content was below 45.95 ± 4.2%. Seeds failed to germinate when their moisture content fell below 27.1 ± 2.1%. Electrical conductivity of seed leachate exhibited a highly significant negative correlation with both germination percentage (p ˂ 0.01, r = -0.926) and moisture content (p ˂ 0.01, r = -0.931). It is concluded that the best substrate for C. acuminata seeds’ germination is the mixture of forest top soil and river sand in a 1/1 (v/v) ratio. Cola acuminata seeds are desiccation-sensitive and their storage behavior is recalcitrant. This is a significant constraint for conservation that should be addressed in further researches.

Keywords: Cola acuminate, seed germination, photoperiod, desiccation tolerance, moisture content, storage behavior.