Life forms of three Senecio species in relation to accumulation and utilization of non-structural carbohydrates

Within the section Jacobaei (Thunb.) Dumort. of the genus Senecio L. the species S. aquaticus L. is a monocarp while S erucifolius L. is a perennial. The life form of S. jacobaea L. is somewhat intermediate, tending more to monocarpism than to perenniality. As a result of flowering, the carbohydrate reserves in all structures of S. aquaticus gradually fall to very low values when the seed is maturing. Following a slight decline in summer, the carbohydrate reserves of S. erucifolius increase from the onset of flowering until the aerial parts die off in autumn. At this time the highest concentrations are found in the rhizomes and the roots. Though decreasing significantly during the generative phase of development, and even when this stage has passed, the carbohydrate reserves of S. jacobaea remain at a relatively high level. Neither S. aquaticus nor S. jacobaea develop specific structures for the storage of carbohydrates, like the rhizomes of S. erucifolius, which facilitate vegetative reproduction. Still, (adventitious) shoots at the roots and stembases may be formed. The carbohydrate reserves of S. aquaticus are insufficient for these shoots to develop into new individuals. Differences between the three species in the changing patterns of soluble carbohydrate reserves reflect the interspecific diversities of life form.