Cork-oak (Quercus suber L.) has great ecological importance for Mediterranean regions, where the species is an essential part of agri-silvicultural and pastoral systems, playing an important role in the economy of marginal areas as well. However, most of the stands are old, since reforestation has been hampered by rural depopulation. Efficient reforestation is also hindered by inadequate supplies of high quality seedlings. The use of nets arranged below the plant foliage and the collection of seeds after forced shedding allowed us to harvest acorns with a higher germinability as compared with seeds traditionally harvested from the ground. However, the latter germinated faster. Cork-oak seeds show recalcitrant behaviour and therefore cannot be desiccated below a high level of moisture content. This hampers the possibility of medium and long-term storage, as it would be necessary to sow acorns during the optimal season of spring (that is about six months after harvest). The critical moisture content, that is the value that seeds should not fall below to maintain high viability, has proved to be about 40%. Below 15-18% moisture content acorns all died, whatever the drying procedure. Seed storage experiments under different temperatures and moisture contents combinations have been conducted. A seed moisture content of 42% proved to be better than 34%, while a temperature of 0°C was more favourable than higher temperatures. After 9 months of storage at 0°C, acorns with 42% moisture content had values of germinability and emergence comparable with those of fresh material. Although cork-oak seeds show a slight dormancy, stratification treatments proved not to be able to improve seed germination. Only in a few cases it was possible to speed up seed germination, but saved time is much less than treatment duration.
Problematiche sementiere e vivaistiche in quercia da sughero
MONTELEONE, Ignazio;BELLETTI, Piero
2002-01-01
Abstract
Cork-oak (Quercus suber L.) has great ecological importance for Mediterranean regions, where the species is an essential part of agri-silvicultural and pastoral systems, playing an important role in the economy of marginal areas as well. However, most of the stands are old, since reforestation has been hampered by rural depopulation. Efficient reforestation is also hindered by inadequate supplies of high quality seedlings. The use of nets arranged below the plant foliage and the collection of seeds after forced shedding allowed us to harvest acorns with a higher germinability as compared with seeds traditionally harvested from the ground. However, the latter germinated faster. Cork-oak seeds show recalcitrant behaviour and therefore cannot be desiccated below a high level of moisture content. This hampers the possibility of medium and long-term storage, as it would be necessary to sow acorns during the optimal season of spring (that is about six months after harvest). The critical moisture content, that is the value that seeds should not fall below to maintain high viability, has proved to be about 40%. Below 15-18% moisture content acorns all died, whatever the drying procedure. Seed storage experiments under different temperatures and moisture contents combinations have been conducted. A seed moisture content of 42% proved to be better than 34%, while a temperature of 0°C was more favourable than higher temperatures. After 9 months of storage at 0°C, acorns with 42% moisture content had values of germinability and emergence comparable with those of fresh material. Although cork-oak seeds show a slight dormancy, stratification treatments proved not to be able to improve seed germination. Only in a few cases it was possible to speed up seed germination, but saved time is much less than treatment duration.
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