TY - JOUR AU - Lopes da Cunha Neto, Israel AU - Angyalossy, Veronica AU - Douglas, Norman A. PY - 2019/10/31 Y2 - 2024/03/29 TI - What are the "sticky rings" on stems of Anulocaulis and related taxa (Nyctaginaceae) from arid regions? JF - Journal of the Botanical Research Institute of Texas JA - J. Bot. Res. Inst. Texas VL - 13 IS - 2 SE - ANATOMY, DEVELOPMENT, AND STRUCTURE DO - 10.17348/jbrit.v13.i2.803 UR - https://journals.brit.org/jbrit/article/view/803 SP - 477-485 AB - <p><em>Anulocaulis</em>, commonly known as “ringstem,” is a small, unusual genus restricted to the Chihuahuan, Sonoran, and Mojave deserts of North&nbsp;America. Here we combined light microscopy and histochemical tests to characterize for the first time the “sticky structures” (here called&nbsp;secretory rings) found on the stem internodes of <em>Anulocaulis</em>. The secretory rings were shown to be groups of epidermal cells, or unicellular&nbsp;glandular trichomes, which largely differ from their neighboring cells both in structure and histochemistry. The cells start to differentiate&nbsp;in early stages of stem development. They begin as regular epidermal cells, but later their anticlinal and external tangential walls start to&nbsp;enlarge. At maturity the cells become remarkably elongated, even balloon-like, with dense cytoplasmic content. Although the secretory&nbsp;rings have been reported as “mucilaginous structures” based on morphological observations, preliminary histochemical analyses showed&nbsp;that its exudate is complex, including a mixture of mucilage, proteins, and phenolic compounds. Future investigations are needed to compare&nbsp;the anatomy of the secretory rings within related genera of Nyctaginaceae and characterize the chemical components of their exudate&nbsp;more specifically to search for potential homologies and adaptive functions of these structures.</p> ER -