FYFD

Tag: osmosis

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    “Dance Dance”

    Artist Thomas Blanchard is no stranger to fluid dynamics. His previous short films focused on mixtures of oil and paint, but in “Dance Dance,” flowers are front and center. There are obvious splashes of color and clouds of diffusion toward the end of the video, but fluid dynamics are there throughout. The oozing, inexorable march of ice crystallizing over petals and leaves has a fluidity that’s heightened by timelapse. It’s a reminder that this phase change is unsteady and full of shifts too subtle to notice in real-time. In the second act, we see flowers blossoming in timelapse, bursting open dramatically before settling in with a subtle shift of their stamens. Motions like these are driven by the flow of fluids inside the plant. By shifting small concentrations of chemicals, plants drive the water in their cells via osmosis. This pumps up cells that cause the petals to spread and unfurl. (Video and image credit: T. Blanchard; via Colossal)

  • How the Jellyfish Stings

    How the Jellyfish Stings

    Many jellyfish are capable of venomously stinging both their prey and their predators. The stings originate from specialized cells in their tentacles called nematocysts (middle image) that, when activated, rapidly extend a thin tubule that acts like a hypodermic needle to deliver venom into the jellyfish’s victim (bottom image). The tubules can elongate in about 50 ms – about one-sixth of the time needed to blink your eye. This rapid extension is driven by osmotic pressure – pressure generated when water flows across a semi-permeable membrane in response to chemical changes. 

    Researchers originally thought all of the osmotic pressure resided in the nematocyst’s capsule end from which the tubule expands, but new work indicates that the tubule is instead pulled along by high osmotic pressure along its moving front. That means that disrupting osmosis at the front – by say, wearing a material with no osmotic potential – can slow down the tubule expansion and stop the jellyfish’s sting. (Image credits: jellyfish – A. Kongprepan; nematocyst – D. Brand; tubule expansion – S. Park et al.; research credit: S. Park et al.; submitted by L. Buss)

  • Spore Squirting

    Spore Squirting

    The fungus Pilobolus spreads its spores with a squirt cannon. Each spore sits on the end of a round fluid-filled pod. Like many plants, the fungus uses a process called osmosis to pump water into the pod. Through osmosis, the fungus increases the concentration of certain molecules inside the pod, which draws water into the pod and increases its pressure. Eventually, the pod ruptures, sending the spore aloft on a jet of fluid that accelerates it at 20,000+g! (Image credit: BBC Earth Unplugged, source; research credit: L. Yafetto et al.)

  • How Plants Move

    How Plants Move

    Though most plants don’t move at speeds that we humans notice, many plants are remarkably active, as seen in the timelapse animations above. Much of this motion is driven by water flow inside the plant. The two plants above are phototropic–they move in response to light. The motion is actuated via a specialized motor cell called the pulvinus, which is located at the base of the leaf where it meets the stem. Unlike animal cells, plant cells have stiff outer walls that allow them to maintain an internal pressure–or turgor pressure–that differs from the outside environment. In fact, it’s not unusual for a plant’s cell to hold a pressure equivalent to 5 atmospheres! The plant manipulates this turgor pressure by controlling the transport of ions across cell membranes. Pump more ions into a cell, and osmosis will cause water to flow into the area of high solute (ion) concentration. This causes the cell to swell and raises the turgor pressure, resulting in the plant’s leaf moving. (Image credit: L. Miller and A. Hoover, source; additional research credit: J. Dumais and Y. Forterre)