BACKGROUND AND AIMS Despite recent progress in elucidating the molecular basis of secondary growth (cambial growth), the functional implications of this developmental process remain poorly understood. Targeted studies exploring how abiotic and biotic factors affect this process, as well as the relevance of secondary growth to fitness of annual dicotyledonous crop species under stress, are almost entirely absent from the literature. Specifically, the physiological role of secondary growth in roots has been completely neglected yet entails a unique array of implications for plant performance that are distinct from secondary growth in shoot tissue. SCOPE Since roots are directly responsible for soil resource capture, understanding of the fitness landscape of root phenotypes is important in both basic and applied plant biology. Interactions between root secondary growth, edaphic conditions and soil resource acquisition may have significant effects on plant fitness. Our intention here is not to provide a comprehensive review of a sparse and disparate literature, but rather to highlight knowledge gaps, propose hypotheses and identify opportunities for novel and agriculturally relevant research pertaining to secondary growth of roots. This viewpoint: (1) summarizes evidence from our own studies and other published work; (2) proposes hypotheses regarding the fitness landscape of secondary growth of roots in annual dicotyledonous species for abiotic and biotic stress; and (3) highlights the importance of directing research efforts to this topic within an agricultural context. CONCLUSIONS Secondary growth of the roots of annual dicots has functional significance with regards to soil resource acquisition and transport, interactions with soil organisms and carbon sequestration. Research on these topics would contribute significantly toward understanding the agronomic value of secondary growth of roots for crop improvement.

中文翻译：

---

根次生生长：土壤资源获取的一个未经探索的组成部分


背景和目的尽管最近在阐明次生生长（形成层生长）的分子基础方面取得了进展，但这种发育过程的功能含义仍然知之甚少。文献中几乎完全没有探索非生物和生物因素如何影响这一过程，以及次生生长与一年生双子叶作物物种在胁迫下适应性的相关性的有针对性的研究。具体而言，根部次生生长的生理作用已被完全忽视，但它对植物性能产生了一系列与芽组织次生生长不同的独特影响。范围 由于根直接负责土壤资源的捕获，因此了解根表型的适应性景观对于基础和应用植物生物学都很重要。根次生生长、土壤条件和土壤资源获取之间的相互作用可能对植物的适应性产生显着影响。我们的目的不是对稀疏且不同的文献进行全面综述，而是强调知识差距，提出假设并确定与根的次生生长相关的新颖和农业相关研究的机会。这一观点：（1）总结了我们自己的研究和其他已发表的著作中的证据； (2) 提出关于一年生双子叶植物根次生生长对非生物和生物胁迫的适应性景观的假设； (3) 强调在农业背景下将研究工作导向该主题的重要性。结论一年生双子叶植物根的次生生长对于土壤资源的获取和运输、与土壤生物的相互作用以及碳固存具有重要的功能意义。 对这些主题的研究将极大地有助于了解根系二次生长对作物改良的农艺价值。