In the proposed project we attempt to clarify the confusion surrounding the developmental origin of lateral roots in Equisetum by making use of Equisetum arvense as a research object. Firstly, to figure out the identity of endodermis and pericycle or double endodermis, as well as the process of lateral root founder cell specification, ontogeny and cell biology experiments will be performed. Then as there is no available genome data, the Spatial Enhanced Resolution Omics Sequencing (Stereo-seq) will be combined with the de novo assembly root transcriptome to align and annotate, aiming to generate a visible gene expression database of Equisetum arvense during the lateral root specification. Basing on above data, up to 500 genes can be validated by Multiplexed Error-Robust Fluorescence In Situ Hybridization (MERFISH). Following, the comparative studies among this species with Arabidopsis, will reveal some homologous transcription factors that show conserved and specific expression patterns in the pericycle. In the absence of transformation method for Equisetum, further functional characterization will be performed in Arabidopsis. This project aims to get insight into the histology and development of Equisetum roots and try to find out whether common conserved and/or clade specific mechanisms are at play during the development of roots and the formation of lateral roots.