Patterns of seed mass variation in the perennial spurge Euphorbia characias (L.) (Euphorbiaceae) in three populations from north-east Spain were examined. Mature inflorescences have a distinctive structure, with a distal umbrella of rays subtending dichotomously grown cyathia. Under the umbrella, cyathia are loosely arranged on rays growing from the bases of leaves. Seed characteristics were studied, especially in relation to position along the inflorescence. Maximum inflorescence height had no effect on seed set or seed mass. Seed set did not differ between populations. Flower position along the inflorescence had a marked effect on seed set and seed mass. Seed set was higher in the distal (upper) portion of the inflorescence. Seeds from the distal area had a greater mass than those from lower parts of the inflorescence. Seeds were planted in the field and observed under natural weather conditions. The bigger seeds from the higher position in the inflorescence produced seedlings with a greater percentage emergence, which, in addition, had an increased percentage establishment than seedlings originating from the smaller seeds from lower areas of the inflorescence. For the three populations considered together, seeds from the basal (lower) portion of the inflorescence were reduced in germination by 51% and establishment by 59%. No differences in seedling dry mass were observed. Seed dispersal-related structures (elaiosome and elaiosome/load ratio) did not vary in relation to position or population. Positional effects on female performance - seed quantity and quality - may be a very strong selective pressure for the peculiar flower disposition in the architecture of E. characias.
|Journal||Seed Science Research|
|Publication status||Published - 17 Oct 2001|
- Euphorbia characias
- Inflorescence architecture
- Positional effect
- Seed set