Leaf and stem anatomy and wood fiber morphology of Seriales (Flacourtia jangomas) at different elevations in La Union, Philippines

Seriales is an underutilized Philippine (Flacourtia jangomas) indigenous fruit tree with ecological and economic potential but limited anatomical evidence across elevation gradients. We quantified leaf and stem anatomy and wood fiber morphology across three low-elevation bands in La Union, Philippines (55–70masl, 71–85masl and 86–100masl). Mature leaves and young stems of F. jangomas were collected, stained, and observed for their leaf and stem anatomical measurements. Wood fibers were macerated and analyzed for fiber length, diameter, lumen diameter, and derived indices. Several leaf traits varied significantly with elevation: lamina and palisade mesophyll were greatest at the lowest site and declined upslope, whereas lower cuticle/epidermis, sclerenchyma, collenchyma, phloem, and collenchyma layers also differed among sites. In contrast, upper cuticle/epidermis, leaf xylem, and spongy mesophyll (~260–303μm) were not significantly different, suggesting conserved internal gas-exchange capacity. Stem anatomy showed decreasing cortex thickness and layer number with elevation, but increasing xylem thickness. Epidermal hairs were longer at the highest site. Wood fiber length shows values similar to tropical species, while mid-elevation trees had smaller fiber and lumen diameters, yielding higher density. High Runkel ratios (>1), low flexibility, and low slenderness indicate poor suitability for pulp and papermaking, but support use for durable woodcraft and small furniture. Overall, F. jangomas exhibits anatomical plasticity within a narrow lowland gradient, showing its resilience and value for lowland agroforestry. This study also highlights the need for conservation of this species and further studies that focus on the effect of climatic factors and stressors.