Horticultural Processes and Bonsai: Respiration

July 24, 2021Bonsaiplace 1 Comment

We have already looked at Photosynthesis https://bonsaiplace.net/2021/07/17/horticultural-processes-and-bonsai-photosynthesis/ and Transpiration https://bonsaiplace.net/2021/07/18/horticultural-processes-for-bonsai-transpiration/ as two processes that are very important for plants and your Bonsai to stay alive. There is a third such process which is as important as the other two, but because the structures responsible for this one are not that visible, it is not that well known. Respiration is something that is done by all living organisms. It basically comes down to the exchange of gasses that is needed to survive, just like in a human being. We breathe in and out to get Oxygen in and to release Carbon dioxide. Well, plants need to do the same thing as Oxygen is needed for plant cells to survive and they also release Carbon dioxide as a waste product.

Intuitively one would then wonder how Photosynthesis and Respiration is balanced so as to make sure that the plant produces more Oxygen than what it will use itself. Respiration can be classified as either Aerobic Respiration (enough Oxygen around) or Anaerobic Respiration (not enough or no Oxygen present). The latter one is a problem for plants and something the Bonsai grower needs to be very aware of. The best example of this is in Yeasts through the process of Fermentation.

Looking at the diagram below, we can see how the two processes interact. The one’s products become the other process’s raw material (input) and vice versa.

Important points for Bonsai growers:

Water logged soil do not allow a good flow of air through the soil which means that there is very little to no Oxygen available for root cells to take this gas in. Due to myriads of bacteria living in soil, and some of these can live anaerobically (in the absence of Oxygen), the chances that these bacteria can cause rot and other damage is large. Best to avoid water logged soil.
Drainage: This aspect is linked to the point above, but important enough to elaborate. Good drainage will promote good airflow through the soil. It is almost like a suction effect in the sense that as water runs through the soil, air will follow and in this way increase the air flow (ventilation) through the soil and the end result is that you have happy roots and happy roots equals happy Bonsai.
Pots: Bonsai pots can be very small in relation to the root mass of the tree planted in it. That means less soil compared to a plant in a garden and this can also lead to less air in the pot. Training pots especially are important. At Bonsaiplace when we use timber boxes or even plastic containers as training pots, we always drill extra holes, not just underneath for drainage purposes, but also from the sides to increase air flow for respiration.
Hothouses and covering Bonsai plants or cuttings with plastic. The main reason why we do this is to increase the humidity around the plant. That helps to prevent water loss through transpiration and increases the heat to promote growth. Just keep in mind that through photosynthesis the plant will produce Oxygen that in turn will be taken up for respiration purposes and Carbon dioxide will be produced for Photosynthesis to take place through Respiration. Where the problem comes in is when you do not have leaves on the plant, i.e., cuttings or a deciduous tree. That means no Photosynthesis and although Respiration needs are low, it still takes place. Just allow fresh air to get into the plastic covering at times and this problem will be sorted.

The next blog will look at Secondary Thickening. This is the process through which plants produce wood and bark. Exactly what we want for our Bonsai trees. To make sure that you do not miss this one, please subscribe to our website and like this post. It is all free.

We can also be found on Facebook as Bonsaiplace and on Instagram as BonsaiplaceNZ. Yes, there is also a You Tube channel as Bonsaiplace.

Horticultural Processes and Bonsai: Transpiration

July 18, 2021July 17, 2021Bonsaiplace 3 Comments

Have you ever wondered how water travels from the soil into the roots and then up the stem to the leaves? Well, here we go. The process is called transpiration and starts in the roots through a process called osmosis. This is the movement of water across a membrane from an area of higher pressure to an area of lower pressure.

Now I am going to confuse you completely. I already said that it starts in the roots, but the condition for the process to happen actually starts in the leaves. As the water accumulates in the leaves, the internal volume of the leaves now have a higher pressure internally compared to the atmospheric air. That means that the water leaves the leaves through a structure called a stoma. There are hundreds of these on the leaves and they can open and close depending on the plant’s water needs and the climate on the outside. Almost like little valves.

Now we have the picture on both ends of the tree. The water flows in through the roots due to water pressure in the soil, it moves up a bit in the tubes (xylem) as these are very thin and act like thin straws. Have you ever noticed how when you place a straw in water how the water level in the thinner straw is higher than the level in the water. That is called capillary pressure.

What now happens is all of these work together. The water is pushed into the roots, the narrowness of the tubes give it a bit of a head start and then the pull from the leaves draws it further up the stem or trunk and the flow happens. This can happen as fast or as slow as the conditions dictate. If everything is perfect, a continuous flow will happen, but as soon as something changes, the tree will adapt. Let’s say there is not enough water in the soil for the osmosis to take place. In other words the pressure is not high enough for the water to enter the roots through the different membranes, well, water will not be taken up and the tree will dry out.

At the other end things can go horribly wrong as well. Let’s say it is a very hot day and a dry warm wind is blowing. That means the pressure on the outside of the leaf is very low and if there is any water inside the leaf, this steep difference will cause water to evaporate or transpire through the stomata and if this happens rapidly and the cells lose their turgidity (pressure), it will wilt and lose structure. If this happens for too long, it is possible that the plant will dry out and leave this earth for Bonsai tree heaven.

Experiment demonstrating plant transpiration. A plastic bag has been secured over the branches of a pot plant. The inside of the bag has condensation on it from water transpired from the plant’s leaves. Transpiration is the evaporation of water from pores called stomata in leaves. The pores open to allow carbon dioxide to enter the plant for use in photosynthesis, but this also leads to the loss of water.

Before we get to the practical things to do and look out for, it is important to remember that water travelling through a plant will contain minerals and other chemicals that it absorbs from the soil. It therefore plays a very important role in the distribution of these minerals throughout the tree.

The practical things:

Watering is a very important part of keeping Bonsai and comes down to a balancing act to ensure that optimal conditions exist for the processes as described above to take place.
Make sure that your trees are placed in an environment that suits the watering needs of the tree. Plants with thin leaves that can dry out easily i.e., Maples and should be kept out of harsh sun and dry windy conditions.
Trees with smaller leaves or even needles (Pines) can withstand this a bit more as they have less stomata and a thick waxy cuticle that covers the leaf or needle to minimise the area exposed to sun and wind and therefore slow transpiration down.
Get to know the water requirements of your trees and if possible group trees with similar water requirements together.
Check the drainage of your trees regularly. This starts with ensuring that the potting medium / soil is correct for the type of plant. Plants that thrive in drier conditions will have to be planted in a coarser and free draining medium.
When watering, water from the top over the whole tree as it washes dirt off the leaves to enhance transpiration as well as photosynthesis. It also cools the plant down so not to lose too much water.
If the soil is too wet, root rot can occur. This is not necessarily due to something going wrong with transpiration, but more a case of the roots not being able to breathe. Yes, they have to breathe as roots consists of living cells and through the process of respiration, need to take in oxygen. More on this in the next article in this series. It is also a perfect living condition for fungus that causes root rot.
Other techniques to ensure the soil does not get too wet is to tilt the pot during long periods of rain for water to run off. You can also push a rod through the drainage holes through to the top to create a channel for water to run through. These are drastic measures only to be used in circumstances where you need to get rid of water quickly.
Soil can dry out very quickly in a small Bonsai pot. When you get to a situation where the soil is so dry that water on top just runs off the surface, break the surface up a bit and dunk the whole pot in a container of water. Wait until all air bubbles disappear and place it back on the bench.
Another thing to look out for is when the roots grow so fast that it basically replaces the soil in the pot and all you have in the pot is a ball of roots. It is difficult for the plant to absorb water under these circumstances. Prevention is better than the cure. Repot with fresh soil when necessary and treat your trees as if they are pets.
When pruning, cover the cuts with cut paste or something similar as you create a wound and in the context of this article, a leak. Plug the plumbing to support the flow of water through the tree.

To receive notification of the other articles in this series on the horticultural processes for Bonsai, like, comment and very importantly, subscribe to this blog.

You can also follow us on Facebook as Bonsaiplace and on Instagram as BonsaiplaceNZ.

Horticultural Processes and Bonsai: Photosynthesis

July 17, 2021July 17, 2021Bonsaiplace 2 Comments

It is a well known fact that horticultural knowledge and skills should be on par with the creative side of Bonsai cultivation as a horticulturally neglected tree will never reach its full potential as a Bonsai. It is therefore important that some basic horticultural knowledge and skills are mastered early on the journey towards Bonsai mastery.

This series of articles has it as goal to highlight a few processes in horticultural science and linking this knowledge to Bonsai creation and maintenance. We will start off with the most important one and that is Photosynthesis. Others will follow in subsequent articles.

Photosynthesis

A bit of knowledge relating to cell science will help here. In plant cells, usually where there is a green colour, you will find cell organelles called chloroplasts. Inside these there is chlorophyll, a colour pigment, and this one is attributed to the green colour in plants. This is where photosynthesis takes place. Photosynthesis is the process through which plants use raw material to produce food. The raw materials are carbon dioxide and water and with the aid of energy from the sun, food is produced and oxygen is made as a by-product of this process.

What does this mean for Bonsai? The most important part here is the exposure to light. Without this natural light source not enough energy will be available for this process. The second part is that there should be enough chloroplasts available for this process to take place. The significance of this comes in at pruning time. It needs to be at the right time as there should be enough energy / food stored to carry the tree through the period with either no leaves or very few leaves, as at this time food production will be limited. This is crucial for evergreens as the food storage or energy storage side of these plants are not as well developed as what it is for deciduous plants. See the process of transpiration in another article as it plays a role with this as well.

In summary:

Your tree should have adequate light for food production.
Your tree should have adequate water for food production. Water plays a role in other processes as well which makes watering a crucial task for healthy Bonsai growing. See transpiration as an example.
Adequate ventilation is necessary to allow atmospheric carbon dioxide to get to your tree. This is usually not a problem in the outdoors, but something to think about when you cover trees with plastic to increase heat and humidity for growth purposes or other climatic defensive reasons.
Pruning and defoliating. Time this right. Never defoliate an evergreen completely unless it is just a branch or two for the purpose of creating deadwood / Jin.
When positioning branches and foliage pads, make sure that top branches do not cover lower branches too much.

Please like or comment on this post and subscribe for regular updates. It will cost you nothing.

Subscribing will help as you will get the updates for the other processes covered in this series. That includes transpiration, respiration, growth, secondary thickening, tropisms and the importance of hormones in all of this.