Coordination of shoot growth with the soil environment by long-distance signalling

Plants constantly integrate information about their environment to control their growth and development. However, the mechanisms by which plants detect and respond to the physical components of their soil environment, such as soil volume, soil depth and the presence of other plants remains widely unknown. Understanding these mechanisms would be highly valuable for generating improvements in crops and perhaps lead to yield enhancements. Soil compaction is a large issue in agricultural contexts, and results in global crop losses. Crops subjected to soil compaction have a reduced soil volume and soil depth. I show that mechanical impedance of the pot wall is unlikely to contribute to the reduced growth seen in plants grown under soil limiting conditions, and instead I propose that a root density sensing mechanism explains reduced plant growth in response to both crowding and limited soil volume. I propose that strigolactones are an exuded signal involved in root density sensing, and show that they modulate shoot growth of neighbouring plants. I describe the ability of plants to make proactive decisions on growth by assessing their soil volume and nutrient availability throughout their lifecycle. These findings have important implications on agricultural practice regarding yield and nutrient use efficiency.