A comparative study of desiccation responses of seeds of three drought-resistant Mediterranean oaks

摘要

The recalcitrance of many Quercus species has received considerable attention. However, considerably less is known about the desiccation sensitivity of drought resistant Mediterranean oaks. The objective of this study was to estimate the seed likelihood sensitivity to desiccation of the three Mediterranean oaks (Quercus coccifera, Quercus pubescens, Quercus pedunculiflora), to see how the severity of desiccation affects acorn moisture content and germination behavior, and to explore any relation of initial acorn characteristics to acorn rate of water loss. Acorns were subjected to variable rates of desiccation after air-drying in room temperature. Results showed that there were significant differences in drying rates between species. Acorn moisturecontent and germination decreased as the severity of desiccation increased, while the germination capacity of Q. pedunculiflora was unaffected from the applied desiccation period, and remained high after 15 days of drying. In Q. coccifera acorns, water loss rate was correlated to the most of acorn morphological characteristics, while for the other two species this correlation was low. The critical moisture content below which Q. coccifera and Q. pubescens seeds start losing their viability is approximately 26%, which is achieved after a drying period of 5 and 7 days, respectively, while for the species Q. pedunculiflora a longer desiccation period should be investigated to find out the minimum critical moisture content.