Matching scientific demonstrations accurately to the explanation of their concepts is important to me. Science is cool, fascinating, and amazing! But even more amazing is scientific literacy and why these demonstrations work the way that they do. It’s essential to match those concepts with clear, accurate concrete examples. Dying the leaves of celery or carnations is a classic science demonstration is the perfect demonstration of a plants vascular system of plants.
This exercise demonstrates the vascular systems of plants. The vascular systems of plants, a collection of cells that create tube-like structures that run up and down the stems and into the leaves, works similarly to our own vascular system, moving water and nutrients throughout bodies. There are two main ‘tubes’ in plants. The xylem moves water and minerals up from the roots into the leaves and other tissues of the plant. The phloem moves glucose from the leaves, where most of the photosynthesis occurs, down throughout the rest of the plant. In college to remember these two terms, we would say, “Xylem up; Phloem down,” remembering that flow and phloem sounded similarly, most things flow down.
Before starting this demonstration, my daughter and I had a discussion reviewing the vascular system of plants from information we had read previously in the week. I then asked her, “If a celery has this vascular system, when we place it into a cup of dyed water, what should happen?” She hypothesized that the celery should take up this dyed water and transport it through its vascular system (in the case the xylem) to the leaves at the top of the plant. Within hours we could see the progression of the dye. By the following day, it was very obvious.
One of the benefits of this demonstration is that the dye also stains the xylem as it moves up through the plant. We took a thin cross section of the celery stalk to examine it. Each of the xylems, a row of small dots along the outer perimeter of the celery stalk, were dyed red. Vascular bundles around the permitter of the stalk is a eudicot characteristic. Monocots have their vascular bundles distributed throughout the stem.
We decided that we wanted to see what these cells look like under the microscope. We took the thinnest slice that we could, and placed it under our microscope. The xylem again was stained red.
This demonstration is a relatively easy one that clearly shows the vascular system for plants. Connecting that explanation creates scientific literacy for our kids.