In vitro ecology of Calopogon tuberosus var. tuberosus (Orchidaceae) seedlings from distant populations: implications for assessing ecotypic differentiation1

Abstract

In vitro culture techniques can be used to study the unique growth habits of plants as well as the ecological factors that influence seedling growth and development (i.e., in vitro ecology) such as adaptation to local environmental conditions. The in vitro seedling ecology of Calopogon tuberosus var. tuberosus from Michigan, South Carolina, and Florida was studied with emphasis on timing of corm formation and biomass allocation. In vitro seedling growth and development were monitored for 20 weeks. Corm formation was most rapid in Michigan seedlings, but was progressively delayed in southern populations. Similarly, biomass allocation to corms was highest in Michigan seedlings while south Florida seedlings exhibited the lowest corm biomass allocation. Shoot senescence in vitro also began earlier in more northern populations. The rapid corm formation and biomass allocation in seedlings from more northern populations represents an adaptive response to a shorter growing season. The relative differences in corm formation, biomass allocation, and shoot senescence in C. tuberosus seedlings suggest that in vitro common garden studies are useful to assess the degree of ecotypic differentiation among populations for a wide range of ecological factors. Additionally, these in vitro techniques can be transferred to numerous species worldwide.