Germination ecology of the aromatic halophyte Artemisia caerulescens L.: influence of abiotic factors and seed after-ripening time

Artemisia caerulescens L. is a rare aromatic perennial shrub growing in saline or brackish environments of the central and western part of the Mediterranean region. On the other hand, despite its distribution in unstable and highly selective environments such as salt marshes, no data are available on its ecological adaptability or on its growth strategy. In an effort to fill these gaps, we performed three experiments in order to evaluate the effects of selected environmental abiotic factors on the seed germination of A. caerulescens. In the first experiment, we determined the effect of different temperatures, photoperiod regimes and salinity on the germination of 120 days old seeds. Secondly, we tested the germination behaviour of the seeds in relation to seed after-ripening time and salinity. The results showed that a temperature regime of 10/20°C and a photothermoperiod of 12/12 h were optimal conditions for seed germination. Salinity affected the final germination rate and mean time to germination. Until 60 days of after-ripening, the seeds exhibited a primary dormancy state. Then, their germination performance was affected by seed after-ripening time and salinity. The data obtained in this study allow us to outline a fairly accurate picture of the ecological requirements of A. caerulescens during germination and of the degree of viability of its seeds at least in the first year of their life. The significant different susceptibility of the seeds to salinity leads to the conclusion that the spread of this species by seeds strongly depends on soil salinity fluctuations. Knowledge of optimal germination requirements could also be useful for the possible use of plant seeds as propagation material in restoration and biodiversity conservation programmes