Do root-sprouting and non-root-sprouting species differ in response to
injury? Effect on growth, root buds and phytohormones
Root-sprouting (RS) clonal herbs are reported to be better adapted to
severe disturbance than other clonal species, and their investments in
clonal and storage organs are smaller than those in rhizomes. RS ability
seems advantageous, so why is it not more common among plants? In a pot
greenhouse experiment, we subjected two closely related clonal herbs
differing in RS ability (RS Inula britannica and rhizomatous I.
salicina) to severe biomass removal and looked for potential barriers to
RS. We confirmed RS only in the already reported RS species I.
britannica. However, RS was not boosted by disturbance in this RS
species, i.e., the number of root buds and sprouts was not affected by
biomass removal. Aerobic root respiration did not differ between the RS
and non-RS species, and the phytohormone profiles differed significantly
more between the RS and non-RS species than between the injured and
non-injured individuals. The common hypothesis, however, never tested,
that RS is facilitated by a low auxins to cytokinins content ratio was
supported. Our results suggest that intrinsic phytohormone regulation is
behind RS ability. Injury-causing phytohormonal imbalance seems to be
less important, at least in spontaneously RS species such as I.