Abstract
Increased mechanical impedance induced by soil drying or compaction causes reduction in plant growth and crop yield. However, how mechanical impedance interacts with nutrient stress has been largely unknown. Here, we investigated the effect of mechanical impedance on the growth of wheat seedlings under contrasting phosphorus (P) supply in a sand culture system which allows the mechanical impedance to be independent of water and nutrient availability. Two wheat genotypes containing the Rht-B1a (tall) or Rht-B1c (gibberellin-insensitive dwarf) alleles in the Cadenza background were used and their shoot and root traits were determined. Mechanical impedance caused a significant reduction in plant growth under sufficient P supply, including reduced shoot and root biomass, leaf area and total root length. By contrast, under low P supply, mechanical impedance did not affect biomass, tiller number, leaf length, and nodal root number in both wheat genotypes, indicating that the magnitude of the growth restriction imposed by mechanical impedance was dependent on P supply. The interaction effect between mechanical impedance and P level was significant on most plant traits except for axial and lateral root length, suggesting an evident physical and nutritional interaction. Our findings provide valuable insights into the integrated effects of plants in response to both soil physical and nutritional stresses. Understanding the response patterns is critical for optimizing soil tillage and nutrient management in the field.
Highlights
Roots are critical for the plant to acquire water and nutrients from soil
The effect of mechanical impedance on wheat growth and morphology was determined by growing plants in the sand column system with contrasting P supply
Three-way Analysis of Variance (ANOVA) showed that the main effects of mechanical impedance and P supply, as well as their interaction effect, on shoot and root biomass were significant at P < 0.001 (Table 1)
Summary
Roots are critical for the plant to acquire water and nutrients from soil. Root structure and function determine soil exploration and exploitation, and have a major impact on nutrient and water uptake, stress tolerance and crop productivity. High soil mechanical impedance leads to root morphological modification, such as the decreased size of the root system and a lower root elongation rate (Bingham and Bengough, 2003), swollen, circular, or flattened root tips (Lipiec et al, 2012), smaller angular spread (Jin et al, 2015), and altered branching patterns depending on plant species (Potocka and Szymanowska-Pulka, 2018). Increased mechanical impedance has been shown to restrict shoot performance, including decreased tiller number (Atwell, 1990; Whalley et al, 2006) and reduced leaf elongation (Coelho Filho et al, 2013; Jin et al, 2015). Previous studies showed that the leaf stunting under impeded soil was impacted by alterations in gibberellin (GA) signalling, with leaf
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