The effect of cutting on reproductive potential of cow parsley Anthriscus sylvestris at different stages of the flowering cycle; a glasshouse experiment, the Netherlands
The umbellifer, cow parsley Anthriscus sylvestris is a herbaceous perennial rosette plant. The rosette usually flowers in the third or fourth year, after which it dies. It can reproduce vegetatively by side rosettes. In the Netherlands, cow parsley is becoming increasingly abundant in nutrient-rich grasslands e.g. road verges and man-made river banks (river dikes), which are usually mown in June and September. Where it dominates, it suppresses grasses and small herbs, and the underlying soil can become more susceptible to erosion, especially along river dikes. Cow parsley control is therefore a legal requirement in areas prone to flooding.
It is hypothesized that the main direction of movement of assimilates (downwards in the vegetative phase and after flowering, and upwards during flowering) within the plant influences its response to defoliation. The aim of this study was to investigate the effects of different cutting regimes on reproduction.
Cutting experiment: On 19 February 1987, 18 cow parsley plants were removed from a road verge near Wageningen, . Fresh weight was determined and they were planted in 6, 1 m² pots and put in the greenhouse. Six were cut off to 6 cm height when: flowering began (3 March); when flowering stems had reached their tallest (24 March); and when flowering had ended (14 April). All plants were harvested 3 weeks after cutting (7 May). Dry weights of the different plant parts (roots, main-rosette taproot, side-rosette taproots, flowering stem, flowers and seeds, leaves of the main rosette, and leaves of the side rosettes) were determined.
The plants in the cutting experiment were compared with the untreated plants of an adult growth experiment (see below). The effect of cutting treatment on the relative allocation of biomass was examined. The three cutting stages were chosen to compare biomass allocation patterns before and after the hypothesized change in main direction of the assimilate movement.
Adult growth experiment: Twenty-four adult plants were collected from the road verge as above. Fresh weight was measured and they were grown in the same conditions as the cutting experiment. Only plants with a single rosette on one taproot were used. Six plants were harvested on four separate dates, and dry weights of the different plant parts were obtained (as above), to enable growth rate and biomass distribution to be established.
Cut when flowering began: Plants cut when flowering began in early March flowered a second time, the inflorescence originating from buds in old leaf axils. The proportion of stem and flowers to total plant dry weight was the same as in normal flowering rosettes. The relative contribution of side rosettes (including taproots) was smaller in those that were cut.
Cut when tallest: Plants cut when flowering stems had reached their tallest did not flower a second time. The flowering rosette formed many side rosettes and was dying by the end of the experiment. There was significantly more biomass in the leaves and
taproots of side rosettes than when cut when flowering began. There was a tendency for more biomass to be in the leaves and taproots of side rosettes than in those from uncut plants.
Cut when flowering ended: Cutting when flowering ended showed a similar pattern to cutting when the flowering stem was at its tallest.
When non-flowering rosettes were cut, they did not show a significantly different pattern of biomass distribution in their side rosettes to these from untreated non-flowering ones. For those cut when flowering ended, biomass allocation to leaves of the main rosette, was less than those from other cuttings, as a result of the more recent defoliation.
Conclusions: Given that the population growth rate of A.sylvestris is enhanced more strongly by clonal propagation than by establishment of new individuals from seeds, populations could be controlled by cutting at the onset of the flowering season. Although this stimulates extra flowering, it diminishes strong vegetative proliferation.
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