bioRxiv · 2026-06-06
Researchers mapped the detailed structure of hydathodes—tiny leaf-tip organs that release water droplets (guttation) in Arabidopsis—finding that their inner tissue is denser and more varied in cell type than previously known, and that the released water carries material from inside the plant's cell walls.
X-ray CT imaging showed hydathode tissue is more densely packed than surrounding leaf tissue and protrudes from the underside of the leaf surface.
Light microscopy revealed the epithem (the core tissue of the hydathode) is heterogeneous—with elongated cells near the veins and rounded cells toward the pore—and is enclosed by a ring of plastid-containing 'boundary cells' resembling mesophyll cells.
Transgenic plants expressing a secreted GFP marker confirmed that guttation droplets contain apoplastic (cell-wall-space) fluid, not just water filtered from the vascular system.
