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Seed germination of four Halimium species [H. atriplicifolium, H.hHalimifolium, H. ocymoides, H. umbellatum] and eight Helianthemum species [H. almeriense pau, H. appeninum.,H. cinereum, H. hirtum, H. marifolium, H. nummularium, H. syriacum, H. squamatum], all cistaceae species from the mediterranean region, was studied after seed storage in liquid nitrogen (Ln, -196C) for four months. In all samples assayed, mechanical scarification of the seed coat was carried out to enhance seed germination. For most samples studied, final germination percentages were unaffected by storage of seeds in Ln, both for intact seeds and for scarified seeds. The germination rate of cryopreserved seeds, expressed as days to reach 50 percent of the final germination percentage, was lower only for four samples of intact seeds and for three samples of scarified seeds. Therefore, this study shows that seed cryopreservation could be a suitable procedure for the long-term seed conservation of several Halimium and Helianthemum species.

The morphometric features, germination requirements (under controlled conditions of light and temperature, and after different pre-sowing treatments) and cryopreservation tolerance of Tuberaria macrosepala (Cistaceae) seeds were studied. Constant (5, 10, 15, 20, 25, 30°C) and alternating temperature regimes (25/15°C, 30/20°C) with 16 h/8 h light/dark photoperiod and constant darkness conditions were used. Mechanical scarification, dry heat, boiling water, soaking in distilled water and soaking in gibberellic acid solution were used as pre-sowing treatments to enhance germination. Tuberaria macrosepala seeds were separated into three groups (light brown, medium brown and dark brown) according to the color of their seed coat. These three types of seeds also differed in size, weight and germinability. Dark brown seeds were found to be inferior to both medium and light brown seeds in size, final germination percentage and germination rate. No significant differences were found in seed weight between the three seed color types. Most seeds of the studied population were light brown. The final germination percentages of this type of seed ranged from 12 to 69%, depending on the temperature and light conditions used. Mechanical scarification significantly improved the final germination percentages of the three seed color types (86–96%). Therefore, seed coat impermeability to water (physical dormancy) appears to be the main cause of seed dormancy present in this species and seed color may be an indicator of hardseededness. Cryopreservation did not significantly decrease the final germination percentages. Therefore, cryopreservation could provide a method for long-term storage of germplasm of this species. [ABSTRACT FROM AUTHOR]