Anatomical structures of Reaumuria soongorica in Alashan Desert

摘要

Reaumuria soongorica endemic to Alashan desert, Inner Mongolia, China is tolerant to extreme arid and saline soil environment that plays a vital role in maintaining environmental sustainability. It possessed unique anatomical structures capable of adaptation to desert environment. In order to understand the relationship between the anatomical structures and its abiotic stress tolerances, this study was designed to examine leaf, stem, and root anatomical structures of R. soongorica from ‘Luanjingtan’, ‘Changliushui’, and ‘Wuliji’ within Alashan desert using paraffin section and scanning electron microscopy analysis. Extreme arid and saline soil profiles of three sampling sites revealed by low soil moisture content and high salt content with negative soil water potential. Extreme arid and saline soil conditions enabled R. soongorica to have more leaf mesophyll cells and in return with more stem cortex cell shrinkage and cellular osmotic adjustment compounds using paraffin section method. Thick leaf epicuticle and small mesophyll cell size were also found which is involved in preventing leaf water loss. Low leaf stomata density (213.68 ± 71.72 mm -2 ), high amount of salt glands (24.5±0.5 mm -2 ), and abundant salt crystals on leaf and stem surface as well as xylem vessels were observed under scanning electron microscopy. Specialized multicellular salt gland was structurally formed by five to seven specialized epidermal cells as an ‘opened flower’ shape to secret extra salt out of leaf. In summary, arid and saline soil in Alashan desert enabled R. soongorica to form succulent leaf with thick cuticles, subsidized stomata with low density, and salt glands to decrease leaf transpiration and reduce salt toxicity to maintain active growth.