Effect of cryopreservation, gibberellic acid and mechanical scarification on the seed germination of eight endemic species from the Canary Islands

Abstract

Summary Seed germination of eight endemic species of the Canary Islands (Descurainia burgaeana, Lavatera acerifolia, Lotus mascaensis, Pimpinella cumbrae, Ranunculus cortusifolius, Scilla haemorrhoidalis, Solanum vespertilio and Spartocytisus supranubius) was studied after seed storage in liquid nitrogen (LN, -196 oC), soaking in gibberellic acid (GA3) and mechanical scarification. Lotus mascaensis and Pimpinella cumbrae are classified as “vulnerable” (VU) and Solanum vespertilio as “critically endangered” (CR) according to the IUCN (International Union for the Conservation of Nature) criteria. The germination trials were carried out under controlled conditions of light and temperature. For six of the eight species studied, the final germination percentages of cryopreserved seeds were higher than those of control seeds (non-cryopreserved seeds). Furthermore for three of the species this increase was significant. On the other hand for two of the species, seeds that had been cryopreserved reached a germination percentage lower (Solanum vespertilio) and equal (Spartocytisus supranubius) to the control seeds, however these decreases were not significant. The germination of Solanum vespertilio was significantly enhanced by soaking of the seeds in gibberellic acid (GA3) and the scarified seeds of Lotus mascaensis and Spartocytisus supranubius reached a significantly higher germination percentage than untreated seeds. The germination rate, expressed by the mean germination time (MGT), was significantly lower for two samples of cryopreserved seeds, three samples of seeds pretreated with GA3 and three samples of scarified seeds. Therefore, this study proves seed cryopreservation is a suitable procedure for the long-term seeds conservation of several endemic species from the Canary Islands. Experimental and discussion The eight species chosen in this study, belonging to seven different plant families, they are all endemic species of Canary Islands (Bramwell and Bramwell, 1990). Descurainia burgaeana Webb ex Schulz (Brassicaceae) and Lotus mascaensis Burch. (Fabaceae) are small shrubs endemics of Tenerife island. The shrubby species Spartocytisus supranubius (L.) Webb & Berth. (Fabaceae) and the small chamaephyte Pimpinella