Professor University of Alberta Edmonton, Alberta, Canada
Abstract: In animals, injury has been shown to impact a variety of behaviours, including foraging. Consequently, injured organisms may choose to forage in less nutritious areas rather than nutrient-denser patches if the less-nutritive areas are deemed safer. Additionally, there is evidence that plants integrate multiple environmental cues to inform their root foraging behaviour, resulting in non-additive responses to novel combinations of stimuli such as stress and predation. Thus, both plants and animals must forage for nutrients, but it is unclear if they respond to stress similarly. Here, we ask how the impact of an acute defoliation stress event affects the phenology of root foraging behaviour and how root foraging behaviour changes before and after defoliation. We grew common sunflower (Helianthus annuus L.) in experimental arenas that allowed for viewing of root growth over time. These arenas had low nutrient background soil and a higher nutrient patch to one side of the individual. Plants were then subject to one of three treatments, the control (no defoliation), half clipped (low intensity), or fully clipped (high intensity). We photographed roots over three weeks (one week prior to the defoliation treatments/two weeks after defoliation).
Our findings suggest that defoliation suppresses the overall amount of root growth, but not the root foraging precision, in sunflower. Consequently, plants depicted reduced growth rates in the week immediately following defoliation but did not show a significant change in root foraging precision. However, all treatments showed a decrease in root foraging precision over the full experimental time period, with the final week of growth depicting all treatments with equivalent growth within a nutrient patch and non-nutrient added area. Together these results illustrate the effect of defoliation and the temporality of recovery from injury in the root foraging behaviour of sunflower.
