Germination of Crithmum maritimum under saline conditions

Crithmum maritimum L. (Umbelliferae) is a perennial maritime herb typically growing in coastal zones of the Mediterranean Region of Europe, western Asia, northwestern Africa and North America. In southeastern Spain it endures high temperatures and drought. The fruits (5-6 mm) are composed of two corky mericarps with a spongy mesocarp, allowing them to float and disperse on water. The effects of photoperiod and salinity on germination were studied in fruits and in naked seeds. Seeds and fruits were placed in growth chambers in two light conditions (12h photoperiod and total darkness) and different saline solutions of NaCl: 0.0, 2.5, 5.0, 7.5, 10.0, 12.5, 15.0, 17.5 and 20.0 dS/m. Results showed that 1) photoperiod does not influence germination, 2) naked seeds and fruits in saline solutions increased weight less than those soaked in distilled water, and 3) no significant differences in weights were observed between naked seeds and fruits when distilled water or 20 dS/m solution were used. On the other hand, significant differences in germination of naked seeds and fruits were found. While fruits did not geminate after being placed in saline solutions : 12.5 dS/m, naked seeds germinated in all conditions, although germination decreased in saline solutions over 15 dS/m. Germination speed was always lower in fruits than in naked seeds, although progressively decreasing with salinity increase. This study suggests that the pericarp of Crithmum maritimum fruits could inhibit seeds from germination in high salinity soil conditions near coastal areas and that decreases of salinity, in the rainy season, enhance germination.