Seed size and seed germination in the Mediterranean fire-prone shrub <Emphasis Type="Italic">Cistus </Emphasis><Emphasis Type="Italic">ladanifer</Emphasis> |
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Authors: | Juan A Delgado José M Serrano Francisco López Francisco J Acosta |
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Institution: | 1.Departamento de Investigación Agroambiental Instituto Madrile?o de Investigación y Desarrollo Rural,Agrario y Alimentario (IMIDRA), Finca “El Encín”,Alcala de Henares, Madrid,Spain;2.Departamento de Ecología, Facultad de Biología,Universidad Complutense de Madrid,Madrid,Spain |
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Abstract: | The germination response of different sized seeds from individuals of a Mediterranean fire-prone shrub (Cistus ladanifer) was investigated in relation to pre-germination heating. A control (no heating), a low temperature during a short exposure
time (50°C during 5 min), a high temperature during a short exposure time (100°C during 5 min) and a high temperature during
a long exposure time (100°C during 15 min) were applied to seeds from different individual plants with different mean seed
weight. These pre-germination treatments resemble natural germination scenarios for the studied species, absence of fire,
low intensity pasture fire, typical Mediterranean shrub fire, and severe fire with high fuel load. Mean seed weight only showed
a marginally significant positive correlation with the proportion of germinated seeds whatever the pre-germination treatment.
These results suggest that seed dormancy is unrelated to seed size and that under the experimental conditions used in this
study, the effect of seed size on seed germination is low. Nevertheless, larger seeds could be favoured in natural conditions,
especially under the high competition scenario which arise after wildfires. Control seeds showed a negative correlation between
seed size and germination velocity suggesting that lighter seeds could take advantage from early germination in recruitment
events in the absence of wildfires. Nevertheless, even the lower pre-germination heating treatment turns this correlation
in not significant, suggesting a strong selection pressure (unrelated to seed size) for early germination after fire events.
In our study, different sized seeds of C. ladanifer seem to perform better under different germination scenarios suggesting that seed size variation could be maintained by the
alternation of recruitments without wildfires and recruitments after wildfire events. |
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Keywords: | Fire regime Germination velocity Hard seed coat Heat shock Seed dormancy |
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