Exploring above- and belowground behavioural responses to nutrients and neighbours in wheat (Triticum aestivum L.)
Creators: Mahal, Habba Faiz
Publisher: name: University of Alberta Library
Year: 2022

<p>Taking in environmental information and responding in ways that maximize their ability to thrive and reproduce, plants exhibit behaviour through constant changes in biomass development and spatial distribution. Studies aiming to map this behaviour often use model plants like sunflowers and Arabidopsis spp. that may behave differently than high-density crop plants. Recent evidence indicates that plants alter root development and spatial distribution when dealing with the interplay of nutrient density and neighbour presence. This is especially relevant in agriculture where monoculture crops of a single genetic makeup force familial competition, potentially reducing yields through decreased competitive effort. However, there is a gap in the research looking at the prevalence of these behavioural traits within wheat, Triticum aestivum L., since most studies emphasize morphological characteristics.<br>
In this study, I explored the above- and belowground behavioural responses of T. aestivum to soil fertility, nutrient distribution, and neighbour presence and identity. We conducted a mesocosm experiment on five Canadian Red Spring Wheat varieties: CDC Titanium, Carberry, Glenn, Go Early, and Villian. These cultivars were either grown alone or with a neighbour: either the same cultivar as a kin treatment or in a pairwise combination with another cultivar as a stranger treatment. The pair-wise combinations of cultivars were fully-factorial, and we planted these treatments in heavily or lightly fertilized soil using slow-release 14:14:14 NPK fertilizer. The fertilizer was either homogeneously mixed throughout the pot or placed in a heterogeneous patch equidistant from both plants.<br>
We found that aboveground biomass shifted growth towards shared aerial space in the pots when a neighbouring plant was absent, but there was no impact of neighbour identity, contrary to what we would have expected with kin selection theory. When looking at belowground factors, the soil nutrient level significantly impacted the shift of biomass, increasing neighbour avoidance when under low nutrient conditions. In addition, homogeneous soil resulted in more growth towards the neighbouring plant. This indicates that belowground environmental changes impact aboveground biomass architecture in T. aestivum. We also looked at the impacts of these factors on fitness outcomes as measured through reproductive effort. Interestingly, none of the soil structure elements or social interactions we investigated had any effect.<br>
Last, we evaluated the effects on belowground plant behaviour by looking at the distribution of roots in five locations in the pots, focusing on the areas between the plants and the edge of the pot and the shared soil space in the centre. Our study shows that soil heterogeneity affected root growth throughout the mesocosms, with homogeneous soil resulting in more roots, with one exception. In heterogeneous treatments, the nutrient patch contained significantly more roots, indicating foraging precision. The effects of nutrient level suggest that the central shared soil space was predominantly affected, with more roots in less fertile soil due to increased foraging. Curiously, our study did not reveal any direct effects of neighbour identity, with neighbour presence only affecting the space opposite the nutrient patch interacting with soil heterogeneity. With fewer roots found here in the heterogeneous treatments with a neighbour, plants allocated more roots in the area when they were not facing resource competition in a small space with a nearby neighbour.<br>
Altogether, these findings provide evidence that T. aestivum responds to changes in its social and soil environments. However, the impact of these factors varies, and more research is required to determine why the neighbour&#39;s presence and identity prompted a lack of results. For example, a highly relevant future study would use intra- and inter-specific competition to determine the genetic distance necessary for a kin/stranger effect within wheat.</p>