Article 84 – ‘Plant husbandry 2’

Hi welcome to Taiga Bonzai, we have discussed what happens below ground with the root system and its functionality, in this article we concentrate on what occurs above ground in the foliage and its production of sugars and starches that feed the root system.

Introduction – photosynthesis is a process used by plants to convert light energy into chemical energy through cellular respiration that can later be released to fuel the plant’s activities. Some of this chemical energy including sugars and starches are synthesized from carbon dioxide and water and stored in carbohydrate molecules. In most cases oxygen is also released as a waste product which stores three times more chemical energy than carbohydrates. 

Photosynthesis process

Light energy – although various species of plant perform photosynthesis in different ways, the process always begins when energy from light is absorbed by proteins in a reaction centre, which contain green chlorophyll and other coloured pigments referred to as chromophores. In plants, these proteins are held inside organelles called chloroplasts, that are most abundant in leaf cells, while in bacteria they are embedded in the plasma membrane.

In these light-dependent reactions, some energy is used to strip electrons from suitable substances including, water and oxygen production. The hydrogen freed via the division of water is used in the creation of two further compounds that serve as short-term stores of energy, allowing its transfer to drive other reactions. These compounds are reduced nicotinamide adenine dinucleotide phosphate (NADPH) and adenosine triphosphate (ATP) namely the ‘energy currency’ of cells.

In plants sugars are synthesised by a subsequent sequence of light-independent reactions referred to as the Calvin cycle. It is here that atmospheric carbon dioxide is incorporated into existing organic carbon compounds, such as ribulose bisphosphate. By using the ATP and NADPH produced by the light-dependent reactions, the resulting compounds are then reduced and removed to form further carbohydrates, including glucose.

The light spectrum – in article nos ’03’ ‘Lighting for bonsai’ we discussed our 3 year research program on different forms of lighting that are used in horticulture production. The reason for this was to find a lighting source that could mimic the spectrum. Included were traditional incandescent bulbs – Tungsten (now removed from the market replaced by energy-saving bulbs) CFLs, (Compact fluorescent lamp) Halogen, HID, (High intensity discharge) HPS, (High pressure sodium) and LED, (Light emitting diode) the latter the only one that could come close to mimicking the light spectrum. 

If we look at the light spectrum shown above, we see a band of colour change from ultra 400 nanometers to infra at 800 nanometers. It is argued in some quarters that plants use the whole light spectrum for growth, this maybe the case in some instances, but in reality plants only use ultra to cyan for growth and red to infra for flower and fruit. The area between ultra and infra approximately 525 to 625 nanometers the middle part of the spectrum called white light is not that beneficial to plants, which has shown to be the case in NASA’s experiments for growing plants in space.

Nutrient movement – soil mediums play an important role in how plants receive nutrients, if the structure is compacted it will severely limit the roots ability to move toward nutrients in addition, it also restricts water movement thus preventing root growth. Properly prepared soil mediums allow for root-run, water movement and drainage, for more on this topic see article nos ’09’ ‘Bonsai soils’. As the roots pump water to the foliage the leaves in return send sugars and starches to the roots, this cooperation between root system and foliage ensure growth and vitality.

The xylem showing nutrient (white) and water (blue) movement

Thus far we have discussed the functionality of the root system below ground (article 82) and now what is above ground – the foliage and its purpose – photosynthesis and transportation of sugars and starches and the importance of light. Although these are crucial elements in bonsai and horticulture production, there are other aspects to focus on including heating, ventilation and water.

Plant husbandry – plants including bonsai endemic to particular regions subjected to the elements of the seasons do not require heating. Established plants will adapt their growth cycles as they have for countless eons moreover, ventilation is not a problem as there is always a constant circulation of air. However, plants from temperate zones (often referred to as indoor plants) do require some form of warmth during the cold times in order to survive and this can cause problems.

For decades building designers and heating engineers have tried to conceal heating systems including radiators by positioning them where they are inconspicuous, usually affixed below windows covered by a shelf. People keep plants on these shelves as it is probably the only natural light source available, but this location is detrimental. (a) Because the constant heat evaporates moisture from the soil medium too quickly and (b) constant watering saturates the root system, which can cause problems such as chlorosis affecting the plants health and vitality.

Turning down the thermostat may help in reducing moisture loss but the area is now at a lower temperature, which can have an effect on the plant’s ability to thrive; the average temperature for most temperate indoor plant varieties is 22 to 26° Celsius. If one moves the plant away from the window area then the problems of light loss becomes apparent, which lessens the performance for photosynthesis and healthy growth; is there a solution to this problem? – Yes move the plants away from direct heat.

Returning to the article nos ’03’ ‘Lighting for bonsai’ you can find many references to different lighting fixtures for example, the Hydroponic full Spectrum CFL grow light bulb a 105 Watt 5500K perfect daylight balanced pure white light bulb H105 costing $24.99. Although this may seem a bargain, do not be tempted because the manufacturers claims are incorrect. These cheaper versions of this type of light bulb are not full spectrum, they only emit red light and not the blue light (ultra) needed for growth.

In addition, much depends on the number of plants in your collection, if large or spread out you will probably need more than one bulb because the footprint (the light arc) of one is not wide enough to cover your plant display. Suspending the lights higher to create a larger light arc reduces the power of the lumens, the closer the light source to the plants the more beneficial it becomes. Plus the added fact that you will have to purchase or create some sort of apparatus to suspend the light fixture.

Moreover cheap bulbs may seem an inexpensive solution but many do not have aluminium heat sink plates and get extremely hot, hence fittings to the power source have to be ceramic not plastic for obvious reasons. Therefore, we urge you to research your needs thoroughly before contemplating any purchase, because the cheaper route is not always the best; it may cost more. The image below is one of our LED lighting fixtures purchased in 2016, it is in use from October to May (8 months for 14 hrs per day) and to date (October 2022) there have not been any problems.

Full spectrum LED light setup

Water – it can be agreed that the only water safe for all plant species is rain water due to the fact that it is pure, soft, uncontaminated and sweet to the taste and if collected in containers can be used without repercussions. However, it is not always possible to collect it if one lives in dwellings where rules restrict this practice, the only other option is to use what comes out of the household tap and this is where the problems begin.

Municipal water or domestic water is full of chemicals including Fluoride (F) that was introduced in the 1940’s to assist in reducing tooth decay, Chlorine (CI) a strong disinfectant added to drinking water as a purification technique. Other chemicals found in tap water include, Mercury (Hg) a by product of mining and industrial practises, Arsenic (As), Lead (Pb) and Glyphosate that are major toxins that can do irreparable damage. To find out more on the problems in using domestic water even for human consumption, read the articles nos ’35’ and ’36’ ‘A Teaspoon of Vinegar’ and ‘A Teaspoon of Vinegar’ Part 2.

If domestic water is all that is available it can still be used but it has to be treated, you will need two plastic containers enough to hold 7 litres of water each. Mark one container ‘alkaline’ for deciduous varieties and the other ‘acid’ for coniferous. The ‘alkaline’ container can be filled from the house tap, but must be left to stand for at least 2 days before use. In the ‘acid’ container add a teaspoon of vinegar (the type does not matter) then fill with water from the same tap, this also has to stand for 2 days before use. The vinegar in the water reacts with the alkaline particles creating black streaks these are not harmful, but it is not advisable to consume it.

Black algae in vinegar treated tap water

Your untreated ‘alkaline’ water is for temperate plants varieties only, never coniferous or any other acid loving species including Magnolia, Azaleas and Rhododendron, use the treated ‘acid’ water for these. In addition, you can use the ‘acid’ solution on temperate and other deciduous plants occasionally, if in doubt read the article nos ’27’ ‘The pH factor’ part I or contact us direct, email address is in the about section under our name and logo. Until next time, BW, Nik.