Li Zhensong, Wan Liqiang, Li Shuo, Li Xianglin, He Feng, Tong Zongyong
Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China.
PeerJ. 2021 Sep 9;9:e11962. doi: 10.7717/peerj.11962. eCollection 2021.
Climate change (rainfall events and global warming) affects the survival of alfalfa ( L.) in winter. Appropriate water management can quickly reduce the mortality of alfalfa during winter. To determine how changes in water affect the cold resistance of alfalfa, we explored the root system traits under different rainfall events and the effects on cold resistance in three alfalfa cultivars. These were exposed to three simulated rainfall events (SRE) × two phases in a randomized complete block design with six replications. The three cultivars were WL168, WL353 and WL440, and the three SRE were irrigation once every second day (D), every four days (D) and every eight days (D). There were two phases: before cold acclimation and after cold acclimation. Our results demonstrated that a period of exposure to low temperature was required for alfalfa to achieve maximum cold resistance. The root system tended toward herringbone branching under D, compared with D and D, and demonstrated greater root biomass, crown diameter, root volume, average link length and topological index. Nevertheless, D had less lateral root length, root surface area, specific root length, root forks and fractal dimensions. Greater root biomass and topological index were beneficial to cold resistance in alfalfa, while more lateral roots and root forks inhibited its ability to survive winter. Alfalfa roots had higher proline, soluble sugar and starch content in D than in D and D. In contrast, there was lower malondialdehyde in D, indicating that alfalfa had better cold resistance following a longer irrigation interval before winter. After examining root biomass, root system traits and physiological indexes we concluded that WL168 exhibited stronger cold resistance. Our results contribute to greater understanding of root and cold stress, consequently providing references for selection of cultivars and field water management to improve cold resistance of alfalfa in the context of changes in rainfall patterns.
气候变化（降雨事件和全球变暖）影响紫花苜蓿在冬季的存活。适当的水分管理可迅速降低紫花苜蓿冬季的死亡率。为了确定水分变化如何影响紫花苜蓿的抗寒性，我们探究了不同降雨事件下的根系特征以及对三个紫花苜蓿品种抗寒性的影响。这些品种在随机完全区组设计中接受三种模拟降雨事件（SRE）×两个阶段，重复六次。三个品种分别为WL168、WL353和WL440，三种SRE分别为每隔两天灌溉一次（D2）、每隔四天灌溉一次（D4）和每隔八天灌溉一次（D8）。有两个阶段：低温驯化前和低温驯化后。我们的结果表明，紫花苜蓿需要一段低温暴露时期才能达到最大抗寒性。与D4和D8相比，D2条件下根系呈人字形分支，且具有更大的根生物量、冠幅、根体积、平均连接长度和拓扑指数。然而，D8的侧根长度、根表面积、比根长、根叉数和分形维数较少。更大的根生物量和拓扑指数有利于紫花苜蓿的抗寒，而更多的侧根和根叉会抑制其越冬能力。紫花苜蓿根系中脯氨酸、可溶性糖和淀粉含量在D2条件下高于D4和D8。相反，D2条件下丙二醛含量较低，表明冬季前较长的灌溉间隔后紫花苜蓿具有更好的抗寒性。在研究根生物量、根系特征和生理指标后，我们得出结论，WL168表现出更强的抗寒性。我们的结果有助于更深入地了解根系与冷胁迫，从而为在降雨模式变化的背景下选择品种和进行田间水分管理以提高紫花苜蓿的抗寒性提供参考。
