Anatomical and Endophytic Fungal Associations in Christisonia tubulosa (Wight) Benth. ex Hook.f. (Orobanchaceae)

Abstract

Christisonia tubulosa (Wight) Benth. ex Hook.f. (Orobanchaceae) is a rare holoparasitic angiosperm distributed in the moist deciduous forests of the Western Ghats, India. The present study documents the vegetative anatomical characteristics and root-associated fungal structures of this species. Anatomical assessments were conducted on the scape, rootstock, and roots using light microscopy and scanning electron microscopy. The scape exhibited a single-layered epidermis, cortex, sclerenchymatous tissue, vascular bundles, and water-storage cells. The rootstock showed a compact epidermal layer, parenchymatous ground tissue, a vascular cylinder, starch grains, and raphides. The root system lacked root hairs, and haustorial attachment to the host root was observed. Fungal observations revealed colonization of the root cortex by hyphae, hyphal coils, and vesicle-like structures resembling those of arbuscular mycorrhizal fungi, as well as septate melanized hyphae, moniliform hyphae, and microsclerotia characteristic of dark septate endophytic fungi. Quantitative assessment showed significant variation in the extent of the observed fungal structures. This study provides a modern anatomical description of the vegetative organs and morphological documentation of root-associated fungal structures in the studied population of C. tubulosa.