Tiller architecture and size determine patterns of seed reproduction in a North American grass with a mixed breeding system

Architecture and allometry describe position-dependent and size-dependent effects, respectively, that determine seed reproduction. The perennial Danthonia compressa in the Catskill Mountains of New York State, USA, produces seeds on terminal panicles from potentially chasmogamous florets in summer and later-maturing axillary seeds from leaf-sheath enclosed cleistogamous florets. Flowering tillers from a shady woodland and a sunny lawn showed strong architectural effects: number of axillary seeds increased while mass per seed decreased from lower to upper nodes along the tiller. Number of axillary seeds and mass correlated with vegetative tiller mass, but not number of terminal seeds or mass. Seed reproduction was strongly determined by tiller architecture and size in D. compressa. Additional research could assess whether green tissues of terminal panicles and spikelets contribute photoassimilates to developing seeds, while subtending leaves on a tiller supply resources to developing axillary seeds. Larger tillers of robust D. compressa plants in favorable conditions improve maternal fitness by increasing number and mass of undispersed axillary seeds which can establish offspring within the parental habitat after tiller disarticulation, thereby maintaining a persistent population.