Kawai Tsubasa, Chen Yinglong, Takahashi Hirokazu, Inukai Yoshiaki, Siddique Kadambot H M
The UWA Institute of Agriculture, The University of Western Australia, Perth, WA, Australia.
School of Agriculture and Environment, The University of Western Australia, Perth, WA, Australia.
Front Plant Sci. 2022 Feb 28;13:830577. doi: 10.3389/fpls.2022.830577. eCollection 2022.
Root systems play a pivotal role in water and nutrient uptake from soil. Lateral root (LR) growth is promoted to compensate for inhibited main root growth. Compensatory LR growth contributes to maintaining total root length (TRL) and hence water and nutrient uptake in compacted soils. However, it remains unclear how shoot and root phenotypic traits change during the compensatory growth and whether there are genotypic variations in compensatory root growth. This study analyzed shoot and root morphological traits of 20 rice genotypes, which includes mutants with altered root morphology, during the vegetative stage using a semihydroponic phenotyping system. The phenotyping experiment detected large variation in root and shoot traits among the 20 genotypes. Morphological changes induced by root cutting were analyzed in six selected genotypes with contrasting root system architecture. Root cutting significantly affected root distribution along vertical sections and among diameter classes. After root cutting, more roots distributed at shallower depth and thicker LRs developed. Furthermore, genotypes with deeper root growth without root cutting allocated more compensatory roots to deeper sections even after root cutting than the genotypes with shallower rooting. Due to the compensatory LR growth, root cutting did not significantly affect TRL, root dry weight (RDW), or shoot dry weight (SDW). To analyze the interaction between crown root (CR) number and compensatory root growth, we removed half of the newly emerged CRs in two genotypes. TRL of YRL38 increased at depth with CR number manipulation (CRM) regardless of root tip excision, which was attributed to an increase in specific root length (SRL), despite no change in RDW. Taken together, the tested rice genotypes exhibited compensatory root growth by changing root distribution at depth and in diameter classes. Reducing CR number promoted root development and compensatory growth by improving the efficiency of root development [root length (RL) per resource investment].
根系在从土壤中吸收水分和养分方面起着关键作用。促进侧根（LR）生长以补偿主根生长受到的抑制。补偿性侧根生长有助于维持总根长（TRL），从而有助于在压实土壤中吸收水分和养分。然而，目前尚不清楚在补偿性生长过程中地上部和根系表型性状如何变化，以及补偿性根系生长是否存在基因型差异。本研究使用半水培表型系统分析了20个水稻基因型在营养生长阶段的地上部和根系形态性状，其中包括根系形态改变的突变体。表型实验检测到20个基因型之间根系和地上部性状存在很大差异。在六个根系结构不同的选定基因型中分析了根切断引起的形态变化。根切断显著影响了垂直剖面和不同直径类别的根系分布。根切断后，更多的根分布在较浅深度，并且发育出更粗的侧根。此外，即使在根切断后，无根切断时根系生长较深的基因型仍比根系较浅的基因型在较深剖面分配更多的补偿性根。由于侧根的补偿性生长，根切断对总根长、根干重（RDW）或地上部干重（SDW）没有显著影响。为了分析冠根（CR）数量与补偿性根系生长之间的相互作用，我们在两个基因型中去除了一半新出现的冠根。无论根尖切除与否，YRL38的总根长在深度上随冠根数量操纵（CRM）而增加，这归因于比根长（SRL）的增加，尽管根干重没有变化。综上所述，所测试的水稻基因型通过改变深度和直径类别的根系分布表现出补偿性根系生长。减少冠根数量通过提高根系发育效率（每资源投资的根长（RL））促进根系发育和补偿性生长。
