When I dig up the soil and drink water from it, I’m pretty sure that I’m going to be sick because of all the bacteria, pollutants and chemicals in this water. I can’t drink tap water, river water, or even the rainwater where I live for this reason, too.
However, somehow when I take water from these sources and feed it to my plants, I can trust that the water I will consume later when I eat the fruits or leaves (in the case of vegetables) from these plants will be safe for me. Why is that?
I guess what I hope to know is: When plants take water from the underground, where do all the bacteria, pollutants and chemicals go? Are they filtered by the root and stem of the plant? Or are they “killed” by some kind of immune system that the plants have?
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EDIT: Thank you everyone for answering. I did not expect so many replies, I think I understand this topic much more now. I used to think that water in fruit is always sterlized and completely safe to drink, but apparently that is not the case.
A lot of comments also asked where I live that I cannot even drink tap water straight from the faucet. It is my understanding that in Europe and North America, tap water is often safe to drink, but that is not the case at all in many developing countries. In fact, I remember being VERY surprised when I first saw American people drinking from fountains in parks or filling up a glass of water straight from the kitchen sink in Hollywood movies.
I live in Vietnam. The tap water here mostly comes from rivers, and it undergoes all the filtration and chemical treatment that we can give it, but we are still recommended to at least boil the water first before drinking.
When I was a kid, we did not even have a system to deliver tap water to every homes, even in the capital city (Hanoi). That was as recent as the early 2000s, (I was born in 1993), and most people used to drink and cook using either water from well or collected rainwater. But nowadays, many wells in my city are found to have lead, arsen and heavy metals in it, and rainwater is recently reported as unsafe to drink basically anywhere on Earth because it had “forever chemicals” in it that will never decomposes and can cause cancer. Tap water and bottled water are basically our only options, though the goverment still recommend boiling tap water or at least filter it one more time before drinking/cooking with it.
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Water enters the root by osmosis. Osmosis is the process by which only water molecules are allowed to pass through the membrane ( along a gradient). Therefore , all bacteria and other substances are filtered by the roots.
>Are they filtered by the root and stem of the plant? Or are they “killed” by some kind of immune system that the plants have?
Both.
Plants are highly efficient at filtration. They are also really good at sequestering different substances in different parts of the plant. They also have immune systems that protect against many kinds of disease threats.
Of course sometimes that can be a problem. If plants sequesters all of the lead they take in from polluted soil into their roots, then if it’s a root vegetable that could be a problem for you when you eat the root. But with fruit, the plant is pretty much going to make sure it’s as clean and uncontaminated as possible.
It’s not always true that the water in a plant is safe for consumption.
It’s true that bacteria in the soil can’t burrow into the plant cells and work their way through the roots and farther into the plant. The cells of the plant are kind of a filter. It’s no different than packaging on food keeping bacteria out — they just can’t fit through the material (in this case, the cell wall of root cells).
With chemicals, it depends on the type of chemical and the heath of the plant. Plants have ways to push out chemicals found in soils that can stress the plant. Particularly metals like lead and arsenic. But if the plant is struggling to stay alive, they will absorb them into the plant.
Other chemicals, it varies. Roots only let through things that dissolve in water, and only if they are below a certain size, which filters out a lot of stuff. But many chemicals dissolve in water can be absorbed by the plant. In a few cases, the plant cells might break them up, and in some cases they might poison the plant, but plenty will just stay in the plant.
Plants are living organisms with their own ‘immune system’
Most of the time when a plant lives to adulthood and is doing well enough to spend energy to reproduce, then it isn’t diseased by its environment
This is only really true of natural things that the plant evolved to deal with, and there are exceptions where diseases/parasites or other contaminants can spread around the food chain
There are also rules about where you can grow strawberries, what you can put on land that is growing food, storage regulations to prevent disease after the plant is dead etc
No it is not always true. While by osmosis, most of the microbes are filtered, heavy metal and other molecules are not. Some of them is biodegradable (pesticide and fertilizer) but heavy metal such as cadmium don’t just disappear. There are reports of rice being contaminated by cadmium
Ok, so I have a question. It is said that the soil is contaminated when human feces are dumped srraigjt i to the grond, without bacterial purification or something like this. But how contaminated? Can palnts be poisonous when growing in this soil? Or it is a myth?
Plants filter a lot of bad shit out of water which in turn provides cleaner forms of nutrients for the animals
Since they cant digest and convert food into energy like we can they pretty much have to filter it out directly from its source
And there’s another benefit, animals that can safely eat their fruits can spread the seeds to other parts of their ecosystem through their digestive system
The opening for nutrients to get into plants through the roots is small and thus only elements and small molecules like water, nitrate ions, and lead can get in through this path. Bacteria and viruses are A LOT bigger and can’t get in. However, lead, and many other metals that can get in such, as cadmium, aluminum, copper, arsenic and iron. Some of these are needed, just like your body need iron, and some aren’t and cause known health problems in humans.
It is worth noting that the plants aren’t absorbing chunks of metal. The metal is in the form of single atoms, typically with a net charge as an ion, in the soil and can thus be taken up with the water.
So the bacteria stay in the soil. Some of the pollutants can be absorbed, with smaller stuf consisting of only a few atoms more likely to be absorbed.
They aren’t necessarily safe.
“Lettuce, Other Leafy Greens, and Food Safety | CDC” https://www.cdc.gov/foodsafety/communication/leafy-greens.html#:~:text=CDC%20estimates%20that%20germs%20on,Salmonella%2C%20Listeria%2C%20and%20Cyclospora.
“Heavy Metal Contamination in Vegetables and Their Toxic Effects on Human Health | IntechOpen” https://www.intechopen.com/chapters/80653
“Study sheds light on how salmonella bacteria infect plants” https://www.downtoearth.org.in/news/food/amp/study-sheds-light-on-how-salmonella-bacteria-infect-plants-62762
“Monitoring of pesticides and heavy metals in cucumber fruits produced from different farming systems – PubMed” https://pubmed.ncbi.nlm.nih.gov/19237184/#:~:text=Heavy%20metal%20contamination%20in%20the,in%20the%20daily%20human%20diet.
You ever saw the inside of life straws? its teeny tiny straws that form a net and catches various shit.
Well, water going from the root to the plant goes under MANY filteration.
First they need to get through the root, osmosis means ONLY water and similar particle sizes can pass through the membrane.
Water travel up a tree trunk not by a large tube, but by specific cell structure in a xylem cell.
Then they have to get through the plant’s own chemical sorting. A fruit plant’s job is not to grow fruit. its job is to grow, then spread its seed. such that water and chemistry distribution is actually controlled by the plant.
TLDR: The pathway from water to fruit is too small for both bacteria and protozoa, plants can also sort out some toxins.
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