# Root stomata in Conium maculatum (Apiaceae): anatomically verified occurrence and a comparative survey across Apioideae

## TL;DR

This study reports the first verified occurrence of stomata on the roots of a plant in the Apiaceae family, challenging the assumption that root stomata are rare or anomalous.

## Contribution

The first anatomically confirmed and reproducible report of stomata on the primary root of Conium maculatum in the Apiaceae family.

## Key findings

- Stomata with guard cells were consistently found on the primary roots of Conium maculatum seedlings.
- Root stomata in C. maculatum represent a consistent species-level anatomical feature.
- The findings suggest the need for broader comparative studies to assess the taxonomic distribution of root stomata in Apiaceae.

## Abstract

Stomata are specialized epidermal structures typically restricted to aerial organs of vascular plants. Their absence on roots has long been regarded as a general anatomical rule. Although rare reports in certain dicotyledonous taxa have described root stomata, these occurrences have been considered transient or developmentally anomalous. Within Apiaceae, no confirmed occurrence has previously been documented. This study aimed to investigate the anatomical presence of stomata on the primary roots of Conium maculatum L. seedlings.

Seedlings of C. maculatum derived from wild-collected populations and genebank accessions were examined using light microscopy. Transverse sections and epidermal surface preparations were prepared to confirm root identity and epidermal features. Taxonomic identity was verified using morphological traits and molecular data (ITS and rps16 sequences).

Morphologically distinct stomata with characteristic guard cells were observed on the primary root. Their distribution was sparse and irregular. Root identity was supported by the overall anatomical organization of the examined sections, including a uniseriate epidermis and a broad parenchymatous cortex. Stomatal complexes were consistently detected across all examined accessions of the species.

This study provides the first anatomically verified and reproducible report of stomata on the primary root of C. maculatum within Apiaceae. These findings expand current knowledge of root epidermal anatomy in the family and indicate that further comparative surveys will be necessary to determine the taxonomic extent of this trait.

Stomata are generally considered absent from roots in vascular plants. In this study, we provide anatomically verified and reproducible evidence of stomata on the primary root of Conium maculatum. Using light microscopy and comparative screening across more than 30 Apiaceae taxa, we show that root stomata represent a consistent species-level anatomical feature in C. maculatum. These findings expand current understanding of root epidermal development in angiosperms.