Department of Plant Science, The Pennsylvania State University, University Park, PA 16802, USA.
Ann Bot. 2013 Jul;112(2):347-57. doi: 10.1093/aob/mcs293. Epub 2013 Jan 17.
A hypothetical ideotype is presented to optimize water and N acquisition by maize root systems. The overall premise is that soil resource acquisition is optimized by the coincidence of root foraging and resource availability in time and space. Since water and nitrate enter deeper soil strata over time and are initially depleted in surface soil strata, root systems with rapid exploitation of deep soil would optimize water and N capture in most maize production environments. • THE IDEOTYPE: Specific phenes that may contribute to rooting depth in maize include (a) a large diameter primary root with few but long laterals and tolerance of cold soil temperatures, (b) many seminal roots with shallow growth angles, small diameter, many laterals, and long root hairs, or as an alternative, an intermediate number of seminal roots with steep growth angles, large diameter, and few laterals coupled with abundant lateral branching of the initial crown roots, (c) an intermediate number of crown roots with steep growth angles, and few but long laterals, (d) one whorl of brace roots of high occupancy, having a growth angle that is slightly shallower than the growth angle for crown roots, with few but long laterals, (e) low cortical respiratory burden created by abundant cortical aerenchyma, large cortical cell size, an optimal number of cells per cortical file, and accelerated cortical senescence, (f) unresponsiveness of lateral branching to localized resource availability, and (g) low K(m) and high Vmax for nitrate uptake. Some elements of this ideotype have experimental support, others are hypothetical. Despite differences in N distribution between low-input and commercial maize production, this ideotype is applicable to low-input systems because of the importance of deep rooting for water acquisition. Many features of this ideotype are relevant to other cereal root systems and more generally to root systems of dicotyledonous crops.
提出了一个假设的理想型，以优化玉米根系的水分和氮素吸收。总体前提是，通过根系觅食与时间和空间上资源可用性的吻合来优化土壤资源的获取。由于水和硝酸盐随时间进入较深的土壤层，并且最初在表层土壤层中耗尽，因此能够快速开发深层土壤的根系将在大多数玉米生产环境中优化水和氮素的捕获。
可能有助于玉米根系深度的特定表型包括：（a）具有大直径主根和少量但长侧根，且能耐受冷土温；（b）许多初生根，具有浅的生长角度、小直径、许多侧根和长根毛，或者作为替代，具有中等数量的初生根，具有陡的生长角度、大直径和少量侧根，并与初始冠根的大量侧枝分枝相结合；（c）具有中等数量的陡生冠根和少量但长侧根；（d）一轮高占有率的支撑根，生长角度略浅于冠根的生长角度，具有少量但长侧根；（e）丰富的皮层通气组织、大的皮层细胞大小、每皮层文件的最佳细胞数量和加速的皮层衰老，导致低皮层呼吸负担；（f）侧枝分枝对局部资源可用性无反应；（g）硝酸盐吸收的低 K(m) 和高 Vmax。这个理想型的一些元素具有实验支持，其他的则是假设的。尽管低投入和商业玉米生产之间的氮分布存在差异，但由于深根对水分获取的重要性，这个理想型适用于低投入系统。这个理想型的许多特征与其他谷类作物的根系以及更普遍的双子叶作物的根系有关。
