Drinking "8x8" of water and watering bonsai
Water as solvent
Water is the solvent that makes all the chemistry in your body happen, and it is the lubricant that makes all the parts move smoothly. Still, there is a lot of debate around the benefits of the 8x8 rule of water consumption. But while the exact amount is debatable, nobody debates that healthy water consumption is essential. Similary, water for plants is critical, but too much water causes problems that may not immediately be apparent.
Hydration and Dehydration symptoms in people.
If you’ve ever participated in a health tracking challenge or used an app to track the number of glasses of water that you have consumed for the day, then you’re probably aware of some of the benefits of consistently drinking enough water. Apart from the need to urinate more frequently, the benefits almost all outweigh the potential downsides. But, you can decide for yourself if the increased athletic performance benefits, better mobility and reduced pain outweigh the hassles of frequent bathroom visits. Mild chronic dehydration is relatively common in people, and most people are not complaining about it.
The problems with drinking too much water.
In 2007 a woman in Sacramento, CA died after drinking over 2 gallons of water in two hours for a radio station contest where she could win a video game console. Water toxicity is the condition where the amount of water in your body exceeds the body’s ability to process it, resulting in a change in the balance of chemicals in your blood and in your brain. Specifically, the most serious danger normally comes from dilution of sodium and potassium ions which affects the ability of cells in the body to absorb nutrients through the cell walls.
Wilting in plants
Wilting is a reaction to inadequate water and serves to reduce water loss, making the leaf surface exposed to less sun and wind. Wilting occurs when the rate of loss of water from the plant exceeds the absorption of water in the plant. This can be the result of too little water availability, or an inability to absorb available water due to poor root health.
Tip burn on leaves or needles.
Even with adequate water uptake and root health, under some conditions certain plants can have water stress that results in browned needles or leaves on the plant. Inability to absorb adequate water can actually be the result of fungal root infections caused by over-watering. This leads to the counter-intuitive situation where you should water your tree less to avoid wilting. However, modern science has created a remedy that will remove root-rot inducing organisms (actually oomyces, not fungus); treat your tree with a drench of root fungicide rated to control soil pathogens that cause root rot, and then follow up with beneficial bacterial strains that inhibit rot.
The problems with overwatering plants.
Overwatering is second only to underwatering as a cause of death in plants. The confined nature of a container means that the conditions that allow success are up to the owner of the plant - too little water may cause wilting and die-back while too much water may cause infection by root pathogens and ultimately the same result. Take care to water when your plant needs water and to allow the soil to dry at least slightly between watering. Different species are adapted to different soil conditions. While a juniper or Grewia may be adapted to a wide variety of soil conditions, Japanese Black pine and other species prefer drier soil and typically suffer when exposed to prolonged wet conditions.
Coffee and alcohol have long been blamed as diuretics, causing dehydration rather than hydration as you might expect from a liquid you consume. Opinions differ on whether or not this is true. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3886980/
Further, opinions on the theory of "8x8" are also not uniform. Is that much water good for you, or could it cause problems that are less severe than "hyponatremia" - combination of conditions where the kidneys cannot excrete enough water to keep up with intake. Less severe problems are often not documented as people recover quickly when the situation does not prove fatal.
Water consumption is probably the single most important thing that you have to do every day to ensure that your body remains healthy, flexible and capable. Watering your bonsai is probably the single most important thing you do on a daily, or at least semi-weekly basis to keep your plant healthy and growing. However, in both cases: People drinking water, and people adding water to plants, excess is best avoided and attention to the signs of danger either from the human body or the plant body are best carefully heeded.