Jewels and Sausages

Over at Wight Rambler Rambling Rob recently reported finding spiderwort Tradescantia growing wild, as a garden escape. This plant has interesting flowers, with stamens covered in a forest of hairs so that the centre of the bloom vaguely resembles a spider - if you’ve got a vivid imagination. Under the microscope the hairs have a beauty all of their own, composed of chains of cells that are almost spherical at the tips of the hairs, resembling a string of jewels (second photo down x100). Further down the hair, towards the base, they look more like a string of blue sausages (third photo down x100). These cells have always been favourite subjects for microscopists because you can easily see the cell contents, including the nucleus that contains the DNA which controls the cell and the cytoplasm that streams around inside the cell, which is full of blue anthocyanin pigment (bottom photo x400)

The Most Important Portals on the Planet

If you peel off a thin layer of cells from the surface of a leaf and mount them in a drop of water on a microscope slide, this is what you see – the leaf breathing pores, or stomata. When they open they allow carbon dioxide in and oxygen out. They are, without doubt, the most important portals on the planet. The carbon dioxide that they let in is turned into sugars that form the basis of our food, either directly from plants or indirectly through the domesticated animals that eat plants. The oxygen that they release allows us to breathe. Somehow they have to balance the passage of gases with conserving water, so they open and close depending on how much water is available. Each stoma is made of two lip-shaped guard cells, that bend apart to create a pore when they inflate with water, but collapse to close the pore when they wilt. The one in the top picture (x400) is open, and in the middle picture (x200) one is open and one is closed. The horizontal rows of narrow cells in the bottom picture (x100) are the veins of the leaf, which in this case came from the garden plant spiderwort Tradescantia virginiana.