Seed Weights and Numbers as a Function of Fruit Size and Subgenus in Some Eucalyptus Species From South-Western Australia

Abstract

The woody fruits of 21 species belonging to four different subgeneric groups in Eucalyptus held contents which consisted of 'particles' that were either fertile or sterile, i.e. 'seeds' or 'ovulodes' respectively. The biggest fruits were 9 times wider than the smallest and more than 200 times heavier. Mean numbers of particles per fruit varied from 49 to 953; mean numbers of seeds per fruit varied from 0.8 to 108.

Rising trends against mean oven-dry wall weight of fruits (i.e. fruits minus contents) were found for mean numbers of particles per fruit, mean particle weight and total weight of fruit contents. Using oven-dry weights of components as an index of the energetic costs of their production, costs per particle rose as fruit weights increased. Costs per seed rose to a maximum for fruits up to a dry weight of nearly 10 g but the four largest-fruited species had a relatively low cost for seeds per unit of wall weight.

Species of Monocalyptus had fewer but bigger particles than species of Symphyomyrtus. Species of Eudesmia occupied an intermediate position.