Each taxon is characterized by a temperature range over which seed germination is possible and this may vary in space and time in relation to climate and ecological conditions. We used thermal modelling to test the hypothesis that thermal thresholds for seed germination can predict germination timing of Mediterranean species along an altitudinal and environmental gradient. Seeds of 18 species were collected in Sardinia from sea level to 1810 m above sea level, and germination tests were carried out at a range of constant (5 to 25°C) and alternating (25/10°C) temperatures. Different dormancy-breaking treatments [gibberellic acid (GA3), cold (C) and warm (W) stratifications and dry after ripening (DAR)] were applied. The annual pattern of soil temperatures was recorded using 24 data-loggers buried close to the study species. The logged soil temperatures distinguished ‘Mediterranean lowland’ from ‘Mediterranean mountain’ species. Although germination was >50% in untreated seeds of most species, GA3 had a positive effect in all species. C either inhibited or had a neutral effect on germination, W did not enhanced seed germination, while DAR had a positive effect only in species from coastal environments. The thermal time constant (S) for 50% germination ranged from 22 to 357°Cd (degree days) above base temperatures (Tb) of –9 to 9°C, depending on species and treatments. Mediterranean lowland species had lower Tb values compared with upland species. This study revealed significant differences in germination thresholds of Mediterranean lowland and mountain species in relation to Tb and S that probably have an impact on germination timing in the field and niche competitiveness.
The Aichi Biodiversity Target 12 aims to prevent the extinction risk of known threatened species and to improve their\ud conservation status by 2020. We present the integrated strategy implemented in the last 10 years for the keystone plant\ud species of Sardinia (Italy, W. Mediterranean Basin), which includes the following activities: conservation status assessment\ud (following the IUCN protocol), ex situ conservation, in situ monitoring and active protection measures. To date, an\ud average of 51.8% of keystone plant species have been subjected to the latter first three activities while, due to the higher\ud costs, only few active conservation measures have been carried out. Considering the activities realised since 2004, we\ud have also predicted the conservation effectiveness towards 2020 and have elaborated an index to evaluate it. Halfway\ud through the strategic plan, we argue that more efforts are needed to guarantee the effective conservation of all threatened\ud plants in Sardinia
Each plant species has particular requirements for seed germination and some of them responding differently to constant and alternating temperature regimes. In this study, the interchangeable effects of different treatments and temperatures on the completion of seed germination of Clematis vitalba were investigated.The seeds were tested over a range of constant (from 5°C to 25°C) and under a fluctuating (25/10°C) temperature regime and, the effect of gibberellic acid (GA 3 ), warm (W) and cold (C) incubation while imbibed, and dry after ripening (DAR) were evaluated. The final germination percentages and the time in days required to reach 50% of germination (T 50 ) were calculated.GA 3 and C significantly enhanced completion of seed germination at all temperatures tested. A strong positive effect of alternating temperature was observed, which triggered completion of seed germination regardless of treatment. Under the fluctuating temperature, the chilled seeds had the most rapid germination. Low germination rates were observed for both control and DAR treatments.Seeds of C. vitalba display a certain degree of dormancy, which can be broken by moist chilling and GA 3 treatments. Moreover, the alternating temperature stimulates the completion of seed germination by satisfying certain physiological requirements for germination under constant temperatures.
Helichrysum microphyllum subsp. tyrrhenicum (Asteraceae) is an endemic taxon of Sardinia and Corsica, where it grows at different altitudes. The objective of this study was to investigate the seed traits and germination behaviour of four Sardinian populations of this taxon located at different altitudes. Seed traits were evaluated, and germination tests were carried out by incubating seeds at a range of constant (5-30 °C) and alternating (25/10 °C) temperatures. The dry after-ripening (DAR) pre-treatment was also applied by storing seed in dry conditions for 3 months at 25 °C. Seed traits and germination behaviour data were statistically analysed to identify if there was a correlation with altitude. Differences in seed size, area and mass among populations were recorded, however, no relationship was found with altitude. High germination percentages were obtained in all populations, both in untreated and DAR seeds, and were positively affected by alternating temperatures. The final germination percentage and time required to reach 50% final germination (T ) showed no relationship with altitude. The differences in seed traits and germination detected among the studied populations of H. microphyllum subsp. tyrrhenicum were not correlated with altitude. This study provides new and important knowledge for this taxon. H. microphyllum subsp. tyrrhenicum is characterised by high germination percentages and low T values and does not seem to require any dormancy-breaking treatment. This species represents a high-potential native plant species that should be considered within environmental management plans.
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