The relationship between achene weight, embryo weight and germination in Taraxacum apomicts

Apomicts provide the opportunity to investigate the variation in achene siz e and performance that is due to factors other than genetic differences bet ween achenes. Achene characteristics of a single capitulum from each of 15 biotypes of apomictic Taraxacum were investigated. Within a capitulum, ache ne fresh weight ranged from 4.45-fold to 13.74-fold. Overall, 59.8% of ache nes germinated. The probability of any one achene germinating was influence d both by its source and by its weight and ranged from 0.049 to 0.902 betwe en capitula and from 0.028 to 0.873 between weight classes. An investigatio n of the relationship between achene parts in three biotypes identified a l inear trend for embryos to acquire a greater proportion of total achene wei ght as achene weight increases. Although the heaviest achenes showed the be st germination, it is predicted that, for a given investment of maternal re sources, seedling number would be maximized by producing achenes of a singl e intermediate weight. (C) 1999 Annals of Botany Company.