PEG infiltration: an alternative method to obtain thin sections of cacti tissues

Exploring the anatomical variability along the stem of cacti requires obtaining high-quality thin sections from hard and soft tissues. Several embedding, infiltration, and sectioning methods have been applied mainly to investigate the harder stem base of cacti, where thin cross-sections are relatively easy to obtain. However, analyzing the variation of anatomical features along cacti stems remains a challenge. Specifically, at the tip of cacti stems, the soft and water-rich dominant tissues are difficult to infiltrate. Here we show results obtained by adapting polyethylene glycol (PEG) infiltration techniques and present a step-by-step description of a fast and hazardous chemical-free method that allows successful cross-sectioning. This infiltration technique may provide a tool to further explore and quantify xylem anatomical trait variation along stems of a wide range of succulent-stemmed taxa.