In this article, Rabbi Shmuel Waldman elucidates how the divine hand is present in every intricate detail within the marvels of nature.

Mimosa pudica (touch-me-not plant) is well known for its rapid, VERY rapid, plant leaf movement. It doesn’t just move; the leaf completely collapses closed. This plant is extremely sensitive. Basically, when the leaf is touched by either a human or an animal, or an insect, and even by heavy winds, (or under extreme heat, and even rain) it will quickly fold up its leaves and become parallel (even) with its stem. (At night it always closes up its leaves.) In other words, the leaves end up looking as if it is lying directly on its stem. See the pictures below. “Quickly”, usually means literally at the exact time the leaves are touched. At least that’s the way it looks to the human eye (in most cases).
The opening and closing of the plant’s leaflets, are controlled by fluid-filled sac-like structures found all over the plant, that are called pulvinus. Firstly, on the actual leaf, there’s a bunch of pairs of smaller leaves (called pinna) that are themselves growing out of the leaves own center stem, which is called the Tertiary Pulvinus – see the picture. Then there’s the secondary pulvinus which is at the base/bottom of a bunch of leaves that grow out of it. See the picture. Then there’s the main pulvinus which is from where a number of secondary pulvinus grow out of.

Now, we must understand that there’s going to be three things that happen for it to work. Firstly, there needs to be the mechanism in place that picks up the stimulus, which in this case is the movement of the plant through either touch or by the other methods described above. Then there’s the transfer of these electro signals to the nearest pulvinus. Once it reaches the pulvinus, something happens that causes the leaves to collapse closed. That’s what happens in a nutshell. Please note that these stimuli can trigger the closing of the leaves nearest to the stimuli, from anywhere on the plant.

Notice the two leaves that folded up.

So, what happens? Altogether, there’s what’s called bioelectrochemical mechanisms that are taking place in the plant. When ANY part of the plant is touched, electrical signals are sent out by the cells that were touched. Unfortunately, I could not find any information about these electric signals since wherever I looked for information it says that they aren’t sure how it works. What receptors there are on the plant that react to touch, they don’t know. Nevertheless, when the signal “somehow” does get to the pulvinus, here’s what happens. The plant cells in the `pulvinus’ respond to this signal by quickly releasing the potassium and water that are in them. You see, what normally holds the leaves open, spread out horizontally, and stiff, (against gravity) is water captured in the small cells found all over the leaves. This is called Turgor pressure.  The cells are like small boxes, or balloons filled with water. When the cells are filled with water, that’s called Turgor pressure. If the water is let out, then the balloon collapses. So, with the speedy massive loss of water, the pulvinus bends over and the leaflets collapse. If the stimulus (like the touching of the leavers) stops, then after about 10-20 minutes the leaves will slowly but surely reopen. It’s like filling up the balloon again with water. Slowly it expands and then stays open. If you were to see this in action you would see just how quickly it works. Very Quick! It’s truly amazing how quick the mechanism works!

If you touch the secondary pulvinus, all the leaves attached to it will collapse shut.  If you touch the main pulvinus, everything attached to it will fold up! Then, there can result in a cascading result of many, many other leaves folding up, due to collisions with one another. These are all safety features to protect the plant as much as possible.

The reasons why Hashem made the leaves fold could be many, but the MAIN reason by far, is so that WE have the opportunity to see His wonders and get into our awareness, the greatness of Hashem! In general, the folding of the leaves helps for a number of things. Firstly, the quick folding up can actually scare an animal away. Then, once folded up, it is obviously very difficult to get to the leaves. In addition, it could help against insect infestation since it will fold up from insect stimuli which would often help dislodge the insect from the leaf as it folds. Also, with the leaves folded it exposes the many thorns that it has on its stems, which also keeps animals away.

But here’s what truly amazing! Researches have done experiments and they have shown that the plant can “learn” to ignore repetitive, unharmful stimuli!!

One scientist, designed an experiment to test whether or not the mimosa plant could become accustomed to a stimulus that over time showed to be harmless and stop reacting to that harmless stimulus. In the experiment, using a special machine, she dropped the plant from a height that would not cause the mimosa plant any damage, again and again, at five second intervals, for 60 times. Initially, as expected, all the leaves folded up from the impact, being the plant is extremely sensitive. She noticed however, that over time, parts of the plant stopped folding its leaves upon impact. Her results were that after a certain amount of drops, the plants completely stopped reacting to the impact. However, some people suggested that maybe the plants mechanism were just too wiped out, too “used up” to open up any more. So, using new plants, she redid the first part of the experiment, where they stopped closing after so many drops, and then she changed the method of stimulus and switched the stimulus and started shaking them, and they immediately started to close up fully. So, noy opening up, had nothing to do with being “too wiped out.  This experiment showed that the Mimosa plants “learned” about their environment and they responded only to harmful stimuli, and what they determined is not (anymore) harmful stimuli they stopped responding to! She repeated the dropping experiment every week for 4 weeks and the plants “remembered that the drop was harmless, and did not react to that stimulus anymore at all. This is absolutely mindboggling! No accident could “remember” and “learn” to “ignore” a particular stimulus. This shows a certain amount of understanding in this brainless plant!! Hashem put into the plant a way to avoid “over working” it, when not needed, and somehow it is able to ignore what became “known” to it as a familiar, unharmful stimulus! Scientists are at a complete loss in being able to explain this miracle.

Every part of this plant shows tremendous, amazing Chochmas Hashem!!

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