Ge Y, Hawkesford M J, Rosolem C A, Mooney S J, Ashton R W, Evans J, Whalley W R
Rothamsted Research, Harpenden, AL5 2JQ, United Kingdom.
São Paulo State University, Botucatu, Brazil.
Soil Tillage Res. 2019 Aug;191:171-184. doi: 10.1016/j.still.2019.04.005.
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 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 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，小麦会经历物理胁迫和养分胁迫的综合影响。以往往往分别研究根系阻抗和水分胁迫，而对于它们之间可能如何相互作用却知之甚少。在本研究中，我们在砂培条件下，研究了在0 - 20 mM硝酸盐的不同硝态氮供应水平下，根系阻抗对三个小麦品种（卡丹扎、西19和营队）生长的影响。该模型系统能够在保持充足水分供应的同时增加土壤强度。在另一个盆栽试验中，我们在壤质砂土中种植相同的小麦品种，让土壤充分干燥以降低水势并增加根系阻抗。该盆栽试验也设置了0 - 20 mM硝酸盐的一系列硝态氮供应水平。一旦幼苗定植，我们限制水分供应，使根系的基质势达到约-200 kPa。土壤干燥使贯入阻力从约300 kPa增加到超过1 MPa。两个实验系统存在差异；与砂培相比，基于土壤的实验中生长量较小。然而，相对于对照而言，实验处理（根系阻抗或停水）的效果是可比的。我们的数据证实，卡丹扎（携带高秆等位基因）的叶片伸长对根系阻抗最为敏感。无论硝态氮供应情况如何，都会出现叶片生长受阻。西19和营队（携带半矮秆等位基因）的叶片伸长对根系阻抗和干旱的敏感性低于卡丹扎。我们认为，在土壤干燥至约-200 kPa的盆栽试验中，关键胁迫因素是根系阻抗而非水分供应。
