Anatomical variation in leaf, stem and petiole of Lagenaria siceraria from southwestern

Abstract

Intraspecific anatomical variation in domesticated plants is expected to concentrate in plastic, surface-exposed characters while core vascular and epidermal architecture remains stable, yet this prediction has rarely been tested across multiple organs simultaneously in a single accession collection. Transverse sections of the leaf midrib, stem and proximal and distal petioles were prepared from 45 accessions of Lagenaria siceraria sampled across four states of southwestern Nigeria and scored for 19 qualitative anatomical characters using a defined codebook. The study tested whether intraspecific anatomical variation in this domesticated cucurbit follows the pattern of peripheral variation against a conserved structural core, and whether anatomical groupings reflect geographic origin. Core architectural characters, including the bicollateral vascular bundle, uniseriate epidermis and striated cuticle, were invariant across all 45 accessions and all four organs, confirming a conserved structural core. Variation was concentrated in midrib outline, trichome complement, petiole outline and stem vascular arrangement. One accession, OY11, separated as a singleton cluster in three independent organ analyses, with a coherent cross-organ profile of reduced cortical elaboration that is unlikely to reflect sectioning artefact. Accessions did not cluster by state of geographic origin in any organ. The results confirm that intraspecific anatomical variation in L. siceraria follows the predicted pattern of peripheral variation against a conserved structural core, and identify trichome complement and petiole bundle arrangement as the most informative characters for distinguishing accessions within the species.