Histological description of Saxifraga paniculata leaves with special focus on structures that release CaCO₃

Abstract

Saxifraga paniculata is a subalpine succulent perennial plant arranged in a rosette that is usually found in shallow soil among limestone rocks. Stereoscopic, light and scanning electron microscopy were used to describe the anatomical structure of S. paniculata leaves, paying special attention to structures related to CaCO₃ (calcium carbonate) release. Anomocytic stomata are unevenly distributed on each leaf face, being absent in the lower third. The basal leaf margin presents translucent pluricellular trichomes of variable length and width. Towards the apical margin, trichomes become teeth. Both trichomes and teeth are completely covered with whitish CaCO₃ crystals. Each tooth has a circular cavity connected to a single hydathode through pores. Clearing treatment revealed camptodromous leaf venation. Anatomical structure shows a bifacial cross-section with spongy mesophyll cells at basal part, becoming heterogeneous at the apex with palisade mesophyll on the adaxial face. Hydathodes are epithematic and connected to outer cavities via two kidney-shaped guard cells showing large substomatal cavity. The epithem is surrounded by a thickened sheath and is formed of highly packed elongated cells with interspersed tracheary elements. CaCO₃ deposits consist of microscopic crystals with varying geometries, of which the rhombus is the basic unit.

Keywords:

• Saxifraga paniculata Mill
• leaf histology
• hydathodes
• epithem
• camptodromus venation pattern
• anomocytic stoma
• calcium carbonate (CaCO₃) and limestome rocks

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

We thank the Universidad de León (Spain) for providing the funds for performing this study.

Funding

We thank the Universidad de León (Spain) for providing the funds for performing this study.