Division of Plant Sciences, University of Missouri, Columbia, Missouri, USA.
Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri, USA.
Plant Cell Environ. 2020 Oct;43(10):2409-2427. doi: 10.1111/pce.13840. Epub 2020 Aug 4.
Maize lateral roots exhibit determinate growth, whereby the meristem is genetically programmed to stop producing new cells. To explore whether lateral root determinacy is modified under water deficits, we studied two maize genotypes (B73 and FR697) with divergent responses of lateral root growth to mild water stress using an experimental system that provided near-stable water potential environments throughout lateral root development. First-order laterals of the primary root system of FR697 exhibited delayed determinacy when grown at a water potential of -0.28 MPa, resulting in longer and wider roots than in well-watered (WW) controls. In B73, in contrast, neither the length nor width of lateral roots was affected by water deficit. In water-stressed FR697, root elongation continued at or above the maximum rate in WW roots for 3 days longer, and was still 45% of maximum when WW roots approached their determinate length. Maintenance of root elongation was associated with sustained rates of cell production. In addition, kinematic analyses showed that reductions in tissue expansion rates with aging were delayed in the longitudinal, radial and tangential planes throughout the root growth zone. Thus, this study reveals large genotypic differences in the interaction of water stress with developmental determinacy of maize lateral roots.
玉米侧根表现出有规定的生长，其分生组织在遗传上被编程以停止产生新的细胞。为了探索在水分亏缺下侧根的确定性是否会发生变化，我们使用一种实验系统研究了两个玉米基因型（B73 和 FR697），该系统在侧根发育过程中提供了近稳定的水势环境，它们对侧根生长对轻度水分胁迫的反应存在差异。在水势为-0.28 MPa 的条件下生长时，FR697 一级侧根的确定性延迟，导致其根系比充分供水（WW）对照的根系更长、更宽。相比之下，B73 侧根的长度和宽度都不受水分亏缺的影响。在水分胁迫的 FR697 中，根伸长继续以 WW 根的最大速率或更高速率维持 3 天以上，当 WW 根接近其确定性长度时，仍为最大速率的 45%。根伸长的维持与细胞产生率的持续有关。此外，运动学分析表明，在整个根生长区，组织扩展率随年龄的降低在纵向、径向和切向平面上都延迟了。因此，这项研究揭示了玉米侧根在水分胁迫与发育确定性相互作用方面存在很大的基因型差异。
