In the field, wheat experiences a combination of physical and nutrient stresses. There has been a tendency to study root impedance and water stress in separation and less is known about how they might interact. In this study, we investigated the effect of root impedance on the growth of three wheat varieties (Cadenza, Xi19 and Battalion) at different levels of nitrate availability, from 0–20 mM nitrate, in sand culture. This model system allows soil strength to be increased while maintaining adequate water availability. In a separate pot experiment, we grew the same wheat varieties in a loamy sand where soil was allowed to dry sufficiently to both reduce water potential and increase root impedance. This pot experiment also had a range of nitrate availabilities 0–20 mM nitrate. Once the seedlings were established we limited water supply to apply a matric potential of approximately −200 kPa to the roots. Soil drying increased the penetrometer resistance from approximately 300 kPa to more than 1 MPa. There were differences between the two experimental systems; growth was smaller in the soil-based experiment compared to the sand culture. However, the effects of the experimental treatment, root impedance or water withholding, relative to the control were comparable. Our data confirmed that leaf elongation in Cadenza (carrying the tall Rht allele) was the most sensitive to root impedance. Leaf stunting occurred irrespective of nitrate availability. Leaf elongation in the Xi19 and Battalion (carrying the semi-dwarf Rht allele) was less sensitive to root impedance and drought than Candenza. We suggest that the critical stress in a pot experiment where the soil was allowed to dry to approximately −200 kPa was root impedance and not water availability.

在田间，小麦要承受物理和营养胁迫。人们一直在研究分离中的根部阻抗和水分胁迫，而对它们如何相互作用的了解还很少。在这项研究中，我们研究了在沙培养中，根系阻抗对三种小麦品种（Cadenza，Xi19和营）在硝酸盐利用率不同（从0至20 mM硝酸盐）下的生长的影响。该模型系统可以在保持足够的水利用率的同时提高土壤强度。在一个单独的盆栽试验中，我们在肥沃的沙土上种植了相同的小麦品种，使土壤充分干燥以降低水势并增加根阻抗。该盆栽试验还具有一系列的硝酸盐可用性，范围为0–20 mM硝酸盐。幼苗一旦建立，我们将限制供水，以向根部施加大约-200 kPa的基质电位。土壤干燥使针入度计的阻力从大约300 kPa增加到超过1 MPa。两种实验系统之间存在差异。与砂培养相比，基于土壤的实验的生长较小。然而，相对于对照，实验处理，根阻抗或水分抑制的效果是可比较的。我们的数据证实，Cadenza中的叶片伸长率很高 然而，相对于对照，实验处理，根阻抗或水分抑制的效果是可比较的。我们的数据证实，Cadenza中的叶片伸长率很高 然而，相对于对照，实验处理，根阻抗或水分抑制的效果是可比较的。我们的数据证实，Cadenza中的叶片伸长率很高Rht等位基因对根阻抗最敏感。不管硝酸盐的可用性如何，都会发生叶片发育不良。Xi19和营（带有半矮小的Rht等位基因）的叶片伸长对根系阻抗和干旱的敏感性不如Candenza。我们建议在盆栽实验中将土壤干燥至大约-200 kPa的临界应力是根阻抗，而不是水分有效性。