Department of Soil Science, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran.
Department of Soil Science, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran.
Plant Physiol Biochem. 2017 Sep;118:107-120. doi: 10.1016/j.plaphy.2017.06.005. Epub 2017 Jun 7.
This study was done to evaluate the effects of the root-colonizing endophytic fungus Piriformospora indica on wheat growth under combined drought and mechanical stresses. Inoculated (colonized) and non-inoculated (uncolonized) wheat (Triticum aestivum L. cv. Chamran) seedlings were planted in growth chambers filled with moist sand (at a matric suction of 20 hPa). Slight, moderate and severe mechanical stresses (i.e., penetration resistance, Q, of 1.17, 4.17 and 5.96 MPa, respectively) were produced by a dead-load technique (i.e., placing a weight on the sand surface) in the root medium. Slight, moderate and severe drought stresses were induced using PEG 6000 solutions with osmotic potentials of 0, -0.3 and -0.5 MPa, respectively. After 30 days, plant physiological characteristics and root morphology were measured. An increase in Q from 1.17 to 5.96 MPa led to greater leaf proline concentration and root diameter, and lower relative water content (RWC), leaf water potential (LWP), chlorophyll contents and root volume. Moreover, severe drought stress decreased root and shoot fresh weights, root volume, leaf area, RWC, LWP and chlorophyll content compared to control. Catalase (CAT) and ascorbate peroxidase (APX) activities under severe drought stress were about 1.5 and 2.9 times greater than control. Interaction of the stresses showed that mechanical stress primarily controls plant water status and physiological responses. However, endophyte presence mitigated the adverse effects of individual and combined stresses on plant growth. Colonized plants were better adapted and had greater root length and volume, RWC, LWP and chlorophyll contents under stressful conditions due to higher absorption sites for water and nutrients. Compared with uncolonized plants, colonized plants showed lower CAT activity implying that wheat inoculated with P. indica was more tolerant and experienced less oxidative damage induced by drought and/or mechanical stress.
本研究旨在评估定殖根内真菌内共生梨形侧耳（Piriformospora indica）对小麦在干旱和机械胁迫组合下生长的影响。将接种（定殖）和未接种（未定殖）的小麦（Triticum aestivum L. cv. Chamran）幼苗种植在充满湿沙的生长室内（基质吸力为 20 hPa）。通过死重技术（即在沙表面放置重物）在根系介质中产生轻微、中度和重度机械胁迫（即渗透率 Q 分别为 1.17、4.17 和 5.96 MPa）。使用聚乙二醇 6000 溶液分别诱导轻微、中度和重度干旱胁迫，其渗透势分别为 0、-0.3 和-0.5 MPa。30 天后，测量植物生理特性和根系形态。Q 值从 1.17 增加到 5.96 MPa 会导致叶片脯氨酸浓度和根直径增加，相对含水量（RWC）、叶片水势（LWP）、叶绿素含量和根体积降低。此外，与对照相比，严重干旱胁迫会降低根和茎的鲜重、根体积、叶面积、RWC、LWP 和叶绿素含量。与对照相比，严重干旱胁迫下的过氧化氢酶（CAT）和抗坏血酸过氧化物酶（APX）活性分别增加了约 1.5 倍和 2.9 倍。胁迫的相互作用表明，机械胁迫主要控制植物的水分状况和生理反应。然而，内生菌的存在减轻了单独和组合胁迫对植物生长的不利影响。由于具有更多的水分和养分吸收部位，在胁迫条件下，定殖植物具有更好的适应性，其根长和体积、RWC、LWP 和叶绿素含量更高。与未定殖植物相比，定殖植物的 CAT 活性较低，这意味着接种 P. indica 的小麦更耐受，并且在干旱和/或机械胁迫下经历的氧化损伤更小。
