#1 Why is Water Important?

In Bonsai, we talk about the importance of watering, but we are often mystified by or overlook the characteristics of the water itself that we nurture our plants with. This has been surprising for me coming from a background in saltwater aquariums where we can often obsess over the exact components of the water we put into our ecosystems. In the pursuit of stability, we strip tap water down to its pure form and then build it back up with exactly the nutrients that are required for the species of invertebrate or fish we wish to nurture. An unexpected swing in water parameters or outside influence on the water chemistry can kill thousands of dollars worth of livestock in minutes. The more laissez-faire approach often taken in bonsai of just spraying whatever comes out of the tap onto our trees comes as a surprise to me, when, on the surface at least, it seems like there could be similar impacts of water quality on the wellbeing of organisms under our care.

In this and the following articles in this series, I’ll be delving deeper into available research about the impact of water and soil chemistry on plant health as well as doing mini labs that you can replicate at home. My hope is that this research will be able to help us form more data driven hypotheses for elevating bonsai tree care, and lead to some practical tips for bonsai hobbyists in their pursuit of healthy, happy plants.

Foundational Knowledge

Starting at the basics, plants uptake water ( H2O ) through the roots [1] where it is used for at least two important functions:

1. As an ingredient in photosynthesis.

2. To move nutrients throughout the plant.

As a reminder, the simplified version of photosynthesis is often written as [2]:

If you remember middle school Biology class then you know that carbon dioxide and water mix in a reaction powered by energy absorbed through the leaves creating glucose (C6H12O6), oxygen, and water. The glucose from photosynthesis is then used for the plant to grow and repair itself.

We’ve established that plants need water, carbon dioxide, and light, but what are these nutrients that water is also helping move throughout the plant? It turns out that what plants need (in general) is pretty well understood and is referred to as the 17 “Essential Elements”. I’ll be writing more in a future article on how this was determined and doing more in depth research on this, but for now just believe the University of Montana’s course on Nutrient Management. [3] In Table 1 below, you can see all of the 17 elements, what they do for the plant, as well as where the plant sources them from.

Table 1. Essential element, role in plant, and source.

Up to 99.5% of the water absorbed into the plant exits the plant through the leaves via transpiration and is not actually needed for it's metabolic processes. [10] Cohesion-Tension theory explains how transpiration (movement of water vapor from the plant into the atmosphere) provides the main force that moves water from the roots to the leaves.

You can think of the process as if there was a vacuum attached to the openings in the leaves (stomata) that sucks water out of the plant. Each water molecule is linked hand in hand with the water molecule behind it in a chain so as the molecule closest to the vacuum gets sucked out, it pulls everything behind it. This force goes all the way down the small tubes within the plant body and helps pull water in through the roots from underground.

This process allows the plant to bring the water it needs for photosynthesis to the leaves where the metaphorical "vacuum" is. As water moves throughout the plant, the nutrients described above hitchhike with the water molecules to where they need to go. The plant needs to open itself up to the atmosphere/our "vacuum" in order to get CO2 and Oxygen for it's metabolic and photosynthetic processes. When the pores in the leaves are open, water vapor transfers back into the environment, starting the great migration.

Isn’t water, water?

Now that we’ve reviewed what water is used for and what plants need besides water, let’s move away from mysterious plant equations and tables for a minute and talk about something a little closer to home. As you probably agree, water is also important for another living organism we are all familiar with… Humans! (Sorry to any non-water based organisms reading this.)

Do you prefer the taste of Dasani over Fiji water? (Guilty!) Have you ever noticed the water from your tap tasted a bit off or have you ever been warned against drinking tap water in certain countries you were traveling in? Of course all of these experiences happen because we’re very rarely drinking 100% pure water.

Many organizations, like the World Health Organization (WHO), study the contents of drinking water and have found there can be hundreds of different organic and inorganic components dissolved or suspended within including [4]:

Organic substances:

• Algae

• Bacteria

• Disinfectants

• Hair

• Herbicides

• Pesticides

Non-organic substances:

• Aluminum

• Ammonium

• Arsenic

• Bicarbonate

• Barium

• Calcium

• Chloride

• Chromium

• Copper

• Cyanide

• Fluoride

• Lead

• Magnesium

• Manganese

• Nitrates

• Phosphate

• Silver

• Selenium

• Silicate

• Sodium

• Sulfate

We experience the different concentrations of these components in our water most directly as differences in the taste or sometimes by getting violently ill! There are many studies done on the health effects of these different substances on humans [5] and these are used as the basis for laws that control the allowable concentrations of these in our water. [6]

What happens to the “not water” in my water?

Ok great, so there’s a bunch of stuff in our water, but if it’s safe for us to drink it’s probably safe for our plants… Right? Not necessarily, remember the laws that govern the quality of our drinking water are based on human needs and might not be indicative of what plants crave. (Lookin’ at you Brawndo!) Comparing the common substances found in tap water to the Essential Elements list, we can see that many of the substances are contributing elements that aren’t necessarily needed by our plants. Even for the elements plants do need, we don't know if it is in a meaningful concentration.

This is important because each time you water a plant, some of the substances dissolved in your water bind to soil particles or stay dissolved in water trapped in spaces between soil particles where they are then available for the plant. [7] Plants absorb water and minerals in the soil through separate mechanisms, so plants don’t “drink” water and all its constituent parts in one big gulp like we do. [8] They are often bringing in individual molecules that they find bound to the soil particles or suspended in water near their roots which we’ve just discovered is where all the “dissolved stuff” in our water is!

Thinking of it in a human context again, it would be like if every time you drank water it also strengthened or weakened functions of your home like eroding your foundation or adding hearty snacks to your pantry. One example you’re all hopefully familiar with of plants benefiting from substances dissolved in water is liquid fertilizers where cations (from salts) like Potassium (K+ in "N-P-K") are brought into the soil and then absorbed into the plant to help fuel growth. [9]

In a Bonsai pot, roots can’t escape to new soil environments or summon new sources of water, so they have to make do with what we give them. I think it is worth examining what is in our water and fertilizer more closely since it directly influences the soil chemistry which is where the plant is obtaining its essential nutrients from.

Conclusion

We water our Bonsai trees sometimes multiple times a day, and with each watering, we are subtly and not so subtly influencing the chemistry of the soil/water solution where the plant draws its water and nutrients from. Elements can’t simply disappear, so when they are added during watering, they have to leave the pot through the drainage hole, get absorbed by the tree, or stick around in the soil. The impacts of this aren’t always immediately apparent as plants are extremely adaptable and can even influence the soil chemistry themselves. I’m hoping we can learn more together about how we can ensure the water we drizzle dotingly on our plants is building them and their loamy homes up instead of breaking them down.

What’s Next?

This first article is the introduction to a series I’m doing on my research into water and soil chemistry and the effect it has specifically for Bonsai. Before we can research what affects tap water has on plants, we need to know what is in our tap water and how much of these substances are there to see if it is even meaningful. The next article will go over some quick and easy ways to measure your water parameters.

Did I get anything wrong in this article? Do you have any opinions on topics you would like me to research or requests for the order of new articles? Please reach out to me on Instagram @TeenyTrees or email me at teenytreesbonsai@gmail.com with comments and suggestions.

P.S. Hopefully this article has gotten you intrigued in Water Chemistry and its relationship with your trees! I love exploring how things work, but I unabashedly acknowledge that living organisms are extremely complex. Despite what I like to think about my Chemical Engineering degree, I’m by no means an expert on Botany or soil science and so I’m not looking to establish some authoritative view through these articles. Instead, I want to examine different potential hypotheses for tree care and expand the awareness we have for how we interact with our trees. I’m always open to feedback and interesting article suggestions.

Citations:

[1] How plants use water (2021) Extension. Available at: https://extension.wvu.edu/lawn-gardening-pests/news/2021/03/01/how-plants-use-water#:~:text=Water%20is%20necessary%20for%20photosynthesis,release%20oxygen%20as%20a%20byproduct. (Accessed: 17 August 2023).

[2] Photosystems I and II (no date) Encyclopædia Britannica. Available at: https://www.britannica.com/science/photosynthesis/Photosystems-I-and-II (Accessed: 17 August 2023).

[3] (No date a) Home - Montana State University Extension. Available at: https://store.msuextension.org/publications/AgandNaturalResources/4449-2.pdf (Accessed: 18 August 2023).

[4] What are total dissolved solids and are they safe to drink? (2022) Quench Water. Available at: https://quenchwater.com/blog/total-dissolved-solids/#:~:text=Total%20Dissolved%20Solids%20(TDS)%20are,liter%20(mg%2FL). (Accessed: 17 August 2023).

[5] (No date) Total dissolved solids in drinking-water - world health organization. Available at: https://cdn.who.int/media/docs/default-source/wash-documents/wash-chemicals/tds.pdf?sfvrsn=3e6d651e_4 (Accessed: 18 August 2023).

[6] Drinking water standards and regulations (2022) Centers for Disease Control and Prevention. Available at: https://www.cdc.gov/healthywater/drinking/public/regulations.html#:~:text=The%20Safe%20Drinking%20Water%20Act%20(SDWA)%20was%20passed%20by%20Congress,suppliers%20who%20enforce%20those%20standards. (Accessed: 17 August 2023).

[7] Oliveira, A.B. de, Alencar, N.L.M. and Gomes-Filho, E. (2013) Comparison between the water and salt stress effects on plant growth and development, IntechOpen. Available at: https://www.intechopen.com/chapters/41315 (Accessed: 17 August 2023).

[8] Libretexts (2021) 36.2c: Movement of water and minerals in the xylem, Biology LibreTexts. Available at: https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Map%3A_Raven_Biology_12th_Edition/36%3A_Transport_in_Plants/36.02%3A_Water_and_Mineral_Absorption/36.2C%3A_Movement_of_Water_and_Minerals_in_the_Xylem (Accessed: 17 August 2023).

[9] (No date a) Absorption of potassium into root cells - leonard - 1985 - ACSESS. Available at: https://acsess.onlinelibrary.wiley.com/doi/10.2134/1985.potassium.c12 (Accessed: 18 August 2023).

[10] Editors, B. (2019) Transpiration - definition, function and examples, Biology Dictionary. Available at: https://biologydictionary.net/transpiration/ (Accessed: 29 August 2023).