Silicon improves root system and canopy physiology in wheat under drought stress

Abstract

Aims: Root system is an important regulator for unevenly distributed below-ground resource acquisition. In a rainfed cropping environment, drought stress (DS) significantly restricts root growth and moisture uptake capacity. The fact that silicon (Si) alleviates DS in wheat is widely reported, but its effects on the wheat root system remain unclear. Methods: The present study investigated the effect of pre-sowing Si treatment on two contrasting wheat cultivars (RAC875, drought-tolerant; Kukri, drought-susceptible) at early growth stages. The cultivars were grown in a glasshouse in a complete randomized design with four replications and two watering treatments. Various root traits and physiological data, including non-destructive infrared thermal imaging for water stress indices, were recorded. Results: Under DS and Si (DSSi), Kukri had a significant increase in primary root length (PRL,44%) and lateral root length (LRL,28.1%) compared with RAC875 having a substantial increase in PRL (35.2%), but non-significant in LRL. The Si-induced improvement in the root system positively impacted canopy physiology and significantly enhanced photosynthesis, stomatal conductance and transpiration in Kukri and RAC875 under DSSi. Canopy temperature was reduced significantly in Kukri (4.24%) and RAC875 (6.15%) under DSSi, while canopy temperature depression was enhanced significantly in both the cultivars (Kukri,78.6%; RAC875, 58.6%) under DSSi. Conclusion: These results showed that Si has the potential to influence below-ground traits, which regulate the moisture uptake ability of roots for cooler canopy and improved photosynthesis under DS. It also suggests a future direction to investigate the underlying mechanisms involved in wheat’s Si-induced root growth and moisture uptake ability.