Many thanks to Tatcher a Hainu@Flickr (aka Eckhard Völcker) of Berlin, Germany, for submitting today’s micrograph via the Botany Photo of the Day Flickr Pool (original image). To view more of Eckhard’s micrography work, visit his site titled Wunderkanone (hint: click on Pflanzen for vascular plant imagery). You can also see a small gallery of his work via Labgrab.
As Eckhard explains in the comments accompanying his photograph, this is a 10x magnification of a cross-sectioned pedicel of a rose. His technique? A microtome, or a machine for slicing tissue (think deli meat slicer, but much smaller), is used to make the even cross-section. The sections are then mounted on microscope slides and stained with a dye (or dyes). Different tissues react to different dyes. Expert (and careful) technique can produce a range of colours, as seen here.
Working from the outside of the pedicel inwards: a red-stained cuticle is subtended by a single cell layer thick epidermis. The next dozen or so cell layers form a band called the cortex, consisting of the outermost ~4 cell thick angular collenchyma (provides supportive structure for new growth) and large, undifferentiated parenchyma. The band of colourful vascular bundles (or water and nutrient transport tissues) are next. At the bottom of this micrograph is another grouping of parenchyma, forming the pith.
Each vascular bundle is surrounded by yellow-stained cells that I believe are sclerified parenchyma; these have developed to provide support and protection to the vascular tissue. The orange-red stained cells are a bundle cap of fibres associated with the nutrient-carrying phloem tissue, which consists of the small densely-packed green-stained cells immediately below. The medium-sized bluish-stained cells toward the inside of each vascular bundle form the tissue called xylem, often associated with water transport (but also carry some nutrients). Between the xylem and phloem tissue is a thin band of vascular cambium, a meristematic (undifferentiated cell generating) tissue that will produce additional xylem and phloem with time.
By the way, if I’m wrong about anything, I’d welcome any corrections — I’m not a plant anatomist, though had I been able to section and stain tissue with the skill that Eckhard has, perhaps I would’ve taken a few more courses on the topic.