Root sprouting in Knautia arvensis (Dipsacaceae): effects of polyploidy, soil origin and nutrient availability

Abstract

Plants able to resprout from roots have a potential bud bank that gets initiated after injury to overcome meristem limitation after loss of all stem parts and to facilitate regeneration. Knautia arvensis is reportedly able to sprout from its roots on arable land, but information is missing regarding such ability in serpentine populations or how it might differ between diploids and tetraploids. We hypothesized that (1) 'ruderal' non-serpentine populations better tolerate severe disturbance than relic, serpentine ones; (2) tetraploid populations resprout more readily than diploids due to enhanced growth of higher ploidy levels; and (3) plants of different ploidy levels from serpentine soils are, for evolutionary reasons, more similar in their response to disturbances than plants from non-serpentine soils. To test these hypotheses, we conducted a pot experiment. Its results do not support our hypothesis that the ability to sprout from roots is a factor driving the spread of new weedy taxa into central Europe or the hypothesis that it is related to polyploidization in the genus Knautia. Both tetraploids and plants from non-serpentine populations regenerated less vigorously than diploids and plants from serpentine populations. However, the genetically closer populations of serpentine origin were more similar in their response to experimental manipula- tions than their genetically distinct non-serpentine counterparts. The success of non-serpentine taxa in disturbed habitats of central Europe might be related to traits other than the ability to resprout.