THE RESOURCE COSTS OF GENDER AND MATERNAL SUPPORT IN AN ANDROMONOECIOUS UMBELLIFER, SMYRNIUM OLUSATRUM L.

SUMMARY In hermaphrodite flowers the various organs are potentially in competition with each other for resources translocated via the peduncle. It is an interesting question to ask: in what proportions does a plant with hermaphrodite flowers allocate various potentially limiting resources between these potentially ‘competing’ organs – between sporophylls and organs of attraction (petals, nectaries) and between stamens and pistils? The question becomes even more interesting in an andromonoecious species in which the plant supplies resources to both male and hermaphrodite (perfect) flowers. In the biennial andromonoecious umbellifer Smyrnium olusatrum L. a constant ratio of one hermaphrodite flower to four staminate flowers was found to be maintained despite a fivefold range in both total flower number and total plant dry wt produced by surgery and nutrient depletion. The allocation of nitrogen, phosphorus and potassium in floral organs was studied in S. olusatrum that had received various experimental treatments. The ratio of resource allocated to sporophylls and to ancillary attractive organs was found to remain relatively constant whereas the allocation to the two types of attractive organs (petals and stylopodia) tended to vary with the experimental manipulations. The relative allocation of nutrient resources to male and female activities was scarcely altered by the treatments. Before fertilization plants distributed a greater (c. fivefold) proportion of phosphorus to male than to female organs. However, the cost of placental support of developing embryos reversed the ratio such that at seed maturity a greater proportion of phosphorus (c. × 2) had been allocated to seed than to stamens.