The effects of shoot apex removal may be used to evaluate the cost of apical dominance and the cost of reproduction in plants. Plants that have shoot apices removed may have lateral meristems released from apical dominance and thus, may out-yield undamaged plants (i.e. overcompensate) either in the year of damage, or in the subsequent growing season, reflecting the cost of leaving apical dominance intact. Shoot apex removal may also reduce or prevent reproduction (undercompensation) in the year of damage, leaving more resources stored and available for greater reproduction (overcompensation) in the subsequent season relative to undamaged plants (reflecting the cost of reproduction for undamaged plants in the previous season). These hypotheses were tested using Lythrum salicaria L. (Lythraceae) as a study species. The effects of pre-flower (early), post-flower (late), and all-season shoot apex removal were recorded in L. salicaria within a natural population. Clipped plants were shorter and more branched than unclipped plants, but failed to outperform unclipped plants (in terms of biomass or reproduction) in either the year of treatment or the subsequent year, indicating no evidence for either a cost of apical dominance or a cost of reproduction in this species. Mean seed mass, however, was greater in pre-flower clipped plants compared with unclipped plants in the year of treatment. The interpretation of these results may involve effects of reduced attractiveness to pollinators (and hence reduced fertilization and seed set) in shorter (clipped) plants. The cost of reproduction may be negligible due to in situ photosynthesis of reproductive structures and enhancement of vegetative photosynthesis during reproduction, as reported for other species.
Plants were chosen randomly and setup in a 2 by 4 full factorial design