THE EFFECT OF INFLORESCENCE BUD REMOVAL ON TUBER PRODUCTION IN HELIANTHUS-TUBEROSUS L (ASTERACEAE)

I investigated allocation to sexual and asexual reproduction in the Jerusalem artichoke, Helianthus tuberosus L. (Asteraceae), a clonal pseudoannual that is an herbaceous ramet for one season, but propagates as a perennial through tubers that quickly dissociate from the parent plant. H. tuberosus ramets grown from tubers allocated 24% of their end-of-season biomass to tubers and 9% to sexual organs, with substantial variation attributable to four genetic lines cultured from eastern Iowa. Experimentally induced failure of sexual reproduction increased allocation to asexual reproduction under common garden conditions. Plants with inflorescence buds removed produced more (82 vs. 69) and larger (4.4 g vs. 3.8 g) tubers than those with unlimited sexual reproduction. Total biomass allocation to reproduction in plants receiving the bud-removal treatment was equivalent to combined allocation to sexual and asexual reproduction in plants that produced flower heads and achenes. This suggests a complete diversion of resources from sexual to asexual reproduction when sexual reproduction is thwarted. Aboveground plant size did not change with treatment. These results suggest a flexible life history that can respond to sexual failure resulting from low pollinator availability or damage to inflorescences from herbivory or weather, with enhanced facultative production of asexual tubers capable of sexual reproduction the following year. Hereditary variation in allocation leaves open the possibility of local adaptation.