HighlightSpecies, storage products, and moisture have large effects on the nature and quantity of volatile emission from dry seeds, but storage time and seed viability do not.

The duration that seeds stay vigorous during storage is difficult to predict but critical to seed industry and conservation communities. Production of volatile compounds from lettuce seeds during storage was investigated as a non-invasive and early detection method of seed ageing rates. Over 30 volatile compounds were detected from lettuce seeds during storage at 35 degrees C at water contents ranging from 0.03 to 0.09 g H(2)O g(-1) dw. Both qualitative and quantitative differences in volatile composition were noted as a function of water content, and these differences were apparent before signs of deterioration were visible. Seeds stored at high water content (L >or=0.06 g H(2)O g(-1) dw) emitted molecular species indicative of glycolysis (methanol+ethanol), and evidence of peroxidation was apparent subsequent to viability loss. Seeds containing less water (0.03-0.05 g H(2)O g(-1) dw) produced volatiles indicative of peroxidation and survived longer compared with seeds stored under more humid conditions. Production of glycolysis-related by-products correlated strongly with deterioration rate when measured as a function of water content. This correlation may provide a valuable non-invasive means to predict the duration of the early, asymptomatic stage of seed deterioration.

Final germination percentages of 25 accessions of Brassicaceae from the UPM (Universidad Politécnica de Madrid) seed bank were evaluated after 38-40 years of storage. The seeds were preserved at temperatures between-5°C and-10°C in flame sealed vials containing dehydrated (blue) silica gel. Seed moisture content ranged between 0.3 and 3% (f.w.b) after storage. Most accessions (ten out of twelve) with high initial (before storage) germination rate (low initial dormancy) maintained these high values almost intact after storage (91-100% germination). In two accessions, seeds had developed a secondary dormancy, which was successfully overcome by scarification. A second set of 13 accessions had low initial germination rates (0-20%, i.e. high initial dormancy). In one accession, dormancy had been broken during storage (92% germination) and in nine accessions germination was significantly enhanced by GA 3 and or scarification. Seed dormancy most often decreases during storage but it may also increase or remain unchanged. The consideration of these dormancy variations is very important when evaluating seed longevity in wild species. The preservation method based on silica gel and low temperature (-5°C and-10°C) has proved highly efficient at least for Brassicaceae. Vials with seeds of 12 additional accesssions had remained at room temperature during 34-39 years and those seeds showed germination percentages that were similar to those preserved in the cold room. This result suggests that temperature might not be as important as expected-at least for medium-term preservation-and supports the possibility of using ultra-dry methods.

Erodium paularense Fern. Gonz. & Izco (Geraniaceae) is a perennial, endemic species of central Spain. The restricted distribution of its three populations has made it necessary to consider measures for conservation. Random amplified polymorphic DNA markers were used to determine genetic variation among and within populations. Sixty‐three per cent of the bands were polymorphic. No population‐specific marker was identified. Cluster analysis based on Jaccard's coefficient of all the individuals grouped most of them according to the present populations. Within‐population variability was of a similar order in the three populations. Highly significant genetic differences between populations were detected through AMOVA. Within population diversity contributed 80–85% to the species diversity, a value typical of an outbreeding plant.

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The aim of this work was to develop an in vitro propagation protocol for the endangered species Thymus lotocephalus using seedlings as explants. Several macronutrient concentrations of Murashige and Skoog medium (MS), cytokinin types and concentrations, and cytokinin/ auxin combinations were tested to assess the shoots' proliferation capacity. Although the best proliferation results were obtained with 6-benzyladenine, high percentages of hyperhidric shoots were observed. Because high proliferation of healthy shoots was observed in MS medium that was free of plant growth regulators, this medium was chosen for proliferation studies. The best rooting results were achieved in MS medium without auxins (92.00 ± 6.11%, 6.54 ± 0.52 and 1.60 ± 0.10 cm regarding rooting frequency, number of roots per shoot and longest roots, respectively) or supplemented with 0.5 mg l -1 indole-3-acetic acid (98.00 ± 2.11%, 11.14 ± 0.75 and 2.40 ± 0.24 cm, respectively). Plantlets were successfully acclimatised to ex vitro conditions with a survival rate of 93.33%. With the development of this micropropagation protocol, an important contribution has been made to the conservation of the endangered species T. lotocephalus.

The aim of the present study was to determine whether the loss of seed germination capacity and vigour in seeds of four wild Brassicaceae species (Brassica repanda, Moricandia arvensis, Rorippa nasturtium-aquaticum and Sinapis alba) during ageing at 45°C and 90% relative humidity was related to changes in lipid peroxidation and membrane integrity. For all of the species, ageing reduced the final germination percentage and increased the length of time required to reach 50% of final germination (T 50 ). Large differences in longevity were observed among the species. The times required for viability to be reduced to 80 and 50% of maximum germination (P80 and P50) were the lowest for B. repanda, and these values were two times longer for M. arvensis and R. nasturtium-aquaticum and five times longer for S. alba compared with B. repanda. A loss of seed viability was not associated with malondialdehyde accumulation, suggesting that lipid peroxidation did not cause seed deterioration under these conditions. However, the conductivity test effectively detected seed deterioration in these wild Brassicaceae species, and membrane permeability correlated with both germination and vigour loss. This correlation may provide a valuable mean for early detection of seed viability in wild Brassicaceae species.

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