Aims To face the challenge of decreasing freshwater availability for agriculture, it is important to explore avenues for developing rice genotypes that can be grown like dryland cereals. Roots play a key role in plant adaptation to dry environments. Methods We examined anatomical and histochemical root traits that affect water acquisition in rice ( Oryza sativa ) and wheat ( Triticum aestivum ). These traits and root growth were measured at two developmental stages for three rice and two wheat cultivars that were grown in pots under three water regimes. Results Wheat roots had larger xylem sizes than rice roots, which potentially led to a higher axial conductance, especially under water-deficit conditions. Suberization, lignification and thickening of the endodermis in rice roots increased with increasing water deficit, resulting in stronger radial barriers for water flow in rice than in wheat, especially near the root apex. In addition, water deficit strongly impeded root growth and lateral root proliferation in rice, but only slightly in wheat, and cultivars within a species differed little in these responses. The stress sensitivity of rice attributes was slightly more prominent at vegetative than at flowering stages. Conclusions Rice root characteristics, which are essential for growth under inundated conditions, are not conducive to growth under water deficit. Although rice roots show considerable plasticity under different watering regimes, improving root xylem size and reducing the radial barriers would be required if rice is to grow like dryland cereals.

中文翻译：

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与小麦的比较揭示了缺水胁迫下水稻的根系解剖和组织化学限制

目标 为了应对农业可用淡水减少的挑战，探索开发可像旱地谷物一样生长的水稻基因型的途径非常重要。根在植物适应干燥环境中起着关键作用。方法我们检查了影响水稻（ Oryza sativa ）和小麦（ Triticum aestivum ）水分获取的解剖学和组织化学根特征。这些性状和根系生长是在三个水稻和两个小麦品种的两个发育阶段测量的，这些品种在三种水条件下在盆中生长。结果小麦根的木质部尺寸大于水稻根，这可能导致更高的轴向电导，尤其是在缺水条件下。水稻根部内胚层的木栓化、木质化和增厚随着水分亏缺的增加而增加，导致水稻中水流的径向障碍比小麦强，尤其是在根尖附近。此外，水分亏缺严重阻碍了水稻的根系生长和侧根增殖，但在小麦中仅略有阻碍，并且一个物种内的栽培品种在这些反应上差异很小。水稻营养期的胁迫敏感性略高于开花期。结论 水稻根系特性对淹水条件下的生长至关重要，但不利于缺水条件下的生长。尽管水稻根在不同的浇水方式下表现出相当大的可塑性，但如果水稻要像旱地谷物一样生长，就需要改善根木质部的大小并减少径向障碍。水分亏缺严重阻碍了水稻的根系生长和侧根增殖，但在小麦中只有轻微的阻碍，并且一个物种内的栽培品种在这些反应中几乎没有差异。水稻营养期的胁迫敏感性略高于开花期。结论 水稻根系特性对淹水条件下的生长至关重要，但不利于缺水条件下的生长。尽管水稻根在不同的浇水方式下表现出相当大的可塑性，但如果水稻要像旱地谷物一样生长，就需要改善根木质部的大小并减少径向障碍。水分亏缺严重阻碍了水稻的根系生长和侧根增殖，但在小麦中只有轻微的阻碍，并且一个物种内的栽培品种在这些反应中几乎没有差异。水稻营养期的胁迫敏感性略高于开花期。结论 水稻根系特性对淹水条件下的生长至关重要，但不利于缺水条件下的生长。尽管水稻根在不同的浇水方式下表现出相当大的可塑性，但如果水稻要像旱地谷物一样生长，就需要改善根木质部的大小并减少径向障碍。水稻营养期的胁迫敏感性略高于开花期。结论 水稻根系特性对淹水条件下的生长至关重要，但不利于缺水条件下的生长。尽管水稻根在不同的浇水方式下表现出相当大的可塑性，但如果水稻要像旱地谷物一样生长，就需要改善根木质部的大小并减少径向障碍。水稻营养期的胁迫敏感性略高于开花期。结论 水稻根系特性对淹水条件下的生长至关重要，但不利于缺水条件下的生长。尽管水稻根在不同的浇水方式下表现出相当大的可塑性，但如果水稻要像旱地谷物一样生长，就需要改善根木质部的大小并减少径向障碍。