The rhizosheath: a potential root trait helping plants to tolerate drought stress

Aims: Rhizosheath is known as a layer of adhering soil particle to the root surface. Despite several speculations, the positive function of rhizosheath in acquisition of water and nutrients from drying soil has not yet been experimentally proven. The objective of this study was to experimentally show whether an enhanced rhizosheath formation could help plants to better access water from drying soil. Methods: Eight wheat cultivars were grown in a sandy-loam soil. When plants were 35 days old let dry soil to a water content at which evident wilting symptoms appeared on the plant leaves. During this drying cycle, soil water content and transpiration rate of plants were gravimetrically measured by weighing the plant pots. At the end of this drying cycle, the roots were excavated out of the soil and the rhizosheath formation was gravimetrically quantified by weighing the soil attached to the root system. Results: The results showed that plant cultivars with greater rhizosheath formation could sustain higher transpiration rates at dry condition (water content of 0.07 cm³ cm⁻³) while the plant cultivars with lower rhizosheath formation suffered from drought stress and reached their permanent wilting points at the same water content. Conclusion: The findings of this study gathered evidence that under severe drought condition plant cultivars with an enhanced rhizosheath formation could better survive by sustaining their transpirational and nutritional demands.