Flower removal increases rhizome mass in natural populations of Alstroemeria aurea (Alstroemeriaceae)

• Loss of flowers, fruits and flowering shoots is common in Alstroemeria aurea.
• The effect of flower and flowering-shoot cutting was evaluated after one growing season.
• Flower removal increased rhizome mass but not plant architecture.
• Plasticity of A. aurea plants is limited by the preformed nature of annual shoots.

Plant architecture and phenotypic plasticity under natural conditions remain little known for many rhizomatous species. This study evaluates, in situ, the plastic responses of Alstroemeria aurea plants from three Patagonian populations to flower or flowering-shoot removal. The size and architecture of treated and untreated plants were assessed. Nutrient contents (N, P and K) were evaluated for rhizomes and roots developed in two successive years. Those plants that were deprived of their inflorescences developed, on average, a heavier rhizome than both control plants and plants from which flowering shoots had been removed. Neither of the two treatments applied altered the number of metamers or the branching pattern of the rhizomes. The contents of N, P and K were higher in rhizomes than in roots. In summer, nutrients were more concentrated in inflorescences and the new rhizome segment than in the rhizome segment developed in the previous year. The idea that fruiting failure in A. aurea promotes resource re-assignment from aerial shoots to rhizomes without altering the architecture of plants is supported. The development of the underground portion of aerial shoots in late summer-autumn allows A. aurea plants to take full advantage of short growth periods, but would impose a limit to plasticity.