Zusammenfassung
Understanding the carbohydrate dynamics of sprouting Cirsium arvense (L.) Scop.
and Sonchus arvensis L. ramets can assist in optimizing perennial weed management.
However, detailed knowledge about general reserve dynamics, minimum values in
reserves (compensation point) and different reserve determination methods remains
sparse. We present novel insights into reserve dynamics, which are especially lacking
for S. arvensis. We uniquely compare root weight changes as a proxy for
carbohydrates with direct carbohydrate concentration measurements using
high-performance liquid chromatography (HPLC). In a greenhouse study, ramets of
two sizes (20 and 10 cm) were planted in pots. Subsequent creeping roots of sprouted
plants were destructively harvested and analyzed for carbohydrates 12 times between
planting and flowering. Efficiency in storing carbohydrates and the replenishing rate
of root weight and carbohydrates was much higher in S. arvensis than in C. arvense.
Thus, our study urges to evaluate perennial weed species individually when
investigating root reserves. Determining root reserves by either using root weight
changes as a proxy for carbohydrates or directly measuring carbohydrate
concentrations by HPLC differed in the minimum values of reserves referred to as
compensation points. For both species, these minimum values occurred earlier based
on root weight than based on carbohydrate concentrations. Cutting ramets into 20 or
10 cm sizes did not significantly affect carbohydrate concentration or root weight
changes for both species. We conclude that any practical applications targeting
perennial weeds by fragmenting roots into small ramets through belowground
mechanical control must be evaluated for trade-offs in soil structure, soil erosion, and
energy consumption.