Biomass allocation among reproductive structures in the dioecious shrub Oemleria cerasiformis--a functional interpretation
1994
Antos, J.A. | Allen, G.A.
1. The allocation of resources among various reproductive structures and functions can suggest the relative importance of past selective pressures in moulding reproductive patterns. 2. To determine how male and female plants of the dioecious shrub Oemleria cerasiformis differ in allocation to reproductive functions, biomass was partitioned among reproductive structures for 20 plants of each sex. 3. Structures contributing to pollinator attraction (petals and hypanthium) were heavier in males than in females. In males, these structures constituted 63% of total reproductive biomass; inflorescence stems and bracts constituted 28%, and the androecium only 9%. In females at flowering, petals and hypanthium constituted 50% of reproductive biomass, inflorescence stems and bracts 37%, and the gynoecium 13%. 4. In females, fruits constituted 87% of the total reproductive biomass at average fruit set (13.7% of pistils). Even with the lowest observed fruit set (4% of pistils), fruit comprised 75% of reproductive biomass overall, and pollinator attraction no more than 4%. Fruit biomass was distributed about equally between pulp (offspring dispersal) and stone (offspring provisioning and protection). A flower can produce up to 150 times its own weight in fruit, thus fruit set is the main factor determining how biomass is distributed among reproductive structures in females. 5. These data support the view that the primary factors influencing the evolution of reproductive allocation are, in males, pollen limitation, and in females, the necessity of provisioning and dispersing offspring.
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