Soil-root-shoot interactions in potato

This study aimed to further understand how potatoes sense their root environment and translate this into signals that are transmitted to the above-ground plant parts to regulate plant performance (photosynthesis), water allocation between plant organs and ultimately tuber yields.

The study combined both greenhouse pot trials (where environmental conditions can be tightly regulated) and field trials to understand physiological mechanisms under typical cropping conditions. The pot trials were used to study general principles of stress signalling and physiological responses to drought and compaction in potato, while field experiments applied these findings in a more realistic setting. Consistent measurement methodologies (e.g. to determine plant and soil water relations) were adopted where practical to facilitate comparisons between experiments, and specialised instrumentation used (e.g. to collect xylem sap from potato roots; to non-destructively determine tuber growth and water content) to collect specific data sets.

 Key findings

• Across a factorial combination of soil drying and compaction treatments, above ground biomass at full ground cover determines yield
• Drought stress reduces the size, but not number, of harvested tubers
• Field-grown plants maintained leaf water potential across a factorial combination of soil drying and compaction treatments, likely by increasing root growth (and thus water uptake) and restricting transpiration (water loss) by closing the stomata
• Drought stress increases leaf and xylem sap abscisic acid concentrations, thereby causing stomatal closure and limiting photosynthesis
• Strigolactones (SL) suppress lateral branching of potato shoots, but don’t influence stomatal conductance irrespective of soil moisture
• Water content of tubers follows a diurnal pattern with decreasing water content in the day and increasing water content at night
• Tuber volume increases only at night even under well-watered conditions
• Water influx at night is necessary for tuber volume growth
• Mild drought stress stops tuber growth