A Fast and Fun Method for Studying Plant Vascular Tissue
Tested Studies in Laboratory Teaching, 2017, Volume 38
Julia A. Emerson
Abstract
Many introductory biology students are relatively uninterested or averse to learning about plants. Therefore, we have incorporated this laboratory exercise into the unit on plant biology in our organismal, introductory biology course, as it encourages students to become actively engaged in their studies of plant anatomy. Students use a simple, inexpensive technique for staining the vascular tissue of plant stems, without having to use lengthy or volatile clearing and staining procedures typical of many published techniques. The activity is highly suitable for courses that have limited time and monetary budgets to devote to lab activities; Table 1 lists the required materials and equipment needed to do this activity. The procedure itself is simple and fast: students use one half of a double-edged razor blade to make thin sections of plant stems, transfer them to a microscope slide and immediately cover each section with a drop of a commercially-available, ink-based stain (the Swartz Lamkins Fungal Stain). The stained sections can then be directly examined on a compound microscope after adding a coverslip. Students are able to generate beautifully-stained sections of rarely-seen arrangements of xylem and phloem in simpler plants, for comparison to sections of angiosperm stems from both monocots and eudicots. We have students in our course work in groups of three or four: they each section one or two different plant stems and also examine the sections made by other students in their group, thereby studying several different types of plant stems during the laboratory period. Examples of plants we have provided to our students include young corn, sunflower and Coleus plants, as well as simpler vascular plants such as whisk ferns (Psilotum) and club mosses (Lycopodium, Figure 1). Instructors may instead choose to have their students collect their own small, herbaceous plants from various campus locations, formulating hypotheses for what the arrangement of the vascular tissues will look like in the collected plants based on preliminary taxonomic classifications. The students can then section and treat the stems with the Swartz Lamkins Stain to test their hypotheses.
