Light Spectrum and Its Role in Calcium Nutrition — AGRITECTURE

Written by: Margit Olle

July 3rd, 2024

What is Tipburn?

Tipburn is known to occur when the lettuces experience undue abiotic stress such as long photoperiods, high light sums, high light intensity, (above 16-17 moles/m2 /day) and conditions that limit transpiration (high relative air humidity and low water availability).

Ca-deficiency is usually related to the inability of the plant to translocate adequate Ca to the affected part, rather than insufficient calcium levels in soil.

Tipburn is a form of necrosis on the outer rim of lettuce leaves, believed to be induced by a deficiency in calcium in these cells resulting in their collapse - death. In addition, bubbling and water-soaked areas with tissue collapse are also known as tipburn on lettuce. Margit Olle pictures of the lettuce tipburn can be seen on Figure 1.   

   

Figure 1. Margit Olle pictures of lettuce tipburn. 

Impact on Yield and Quality

With this lighting model we could increase Ca content in plants at least 10 - 20%. It is assumed all measured values (counted just below) will increase 5-10% minimum. 

• Yield, including overall biomass assessment: through better nutrient uptake, stronger plant and less pests and diseases. Therefore, less fertilizers and pesticides usage are foreseen. The yield can increase up to 20% or more of production to cover the loss normally occurring due to this physiological calcium deficiency disorder
• Biotic stresses. Decreased disease and insect attacks about 10% due to stronger leaves, because pests can not invade stronger plant tissues. 
• Nutrient uptake can arise about 10%. First of all, light spectrum effect on Ca content and dynamics through the growing season. 
• Storability: plants are with higher storability when containing more calcium. Storability can increase up to 50%, it means that if normal storage period is 10 days, and the prolongation is 50% then the storage period can be up to 15 days. 
• Plants are with up to 50% higher transportability, when containing more calcium.

The Importance of Calcium in Plant Health

Ca is an essential plant mineral. A high proportion of Ca can be found in vacuoles. A Ca signal is involved in the regulation of cell division. Ca ion is established as a second messenger in numerous plant signalling pathways. Ca controls cell expansion. Ca is required as a cofactor in many enzymes.  Ca also plays a significant role in the processes of seed germination. Ca is very important for photosynthesis. Ca and other cations precipitate with oxalate in shoot cells as oxalate crystals. Ca is required for various structural roles in the cell wall and membranes. The amount of Ca in soil solution are usually high enough to cover plant demands. Ca deficiency in plants is a physiological disorder and occurs rarely as a cause of low Ca levels in soils. The deficiency symptoms on plants do not generally disappear by raising the Ca levels in soils. Therefore, it is important to know the mechanisms of Ca2+ uptake, transport and distribution in plants.

• The benefits of increasing calcium content:
  • reduced tipburn losses, 
  • decreased diseases and pest attacks, 
  • improved quality and storability of lettuce.

 

Light Spectra and Plant Growth - Tables

Light is the sole source of energy for plant growth and development. Light is just one portion of the various electromagnetic spectrum. Terrestrial sunlight is considered to consist of ultraviolet (UV), visible (light) and infra-red light. The wavelengths of UV radiation (UVR) lie in the range of 100-400 nm; UV light is further subdivided into: UVA (ultraviolet A radiation, 315-400 nm), UVB (ultraviolet B radiation, 280-315 nm), and UVC (ultraviolet C radiation, 100-280 nm). Visible light ranges from low blue to far-red with wavelengths between 380 and 750 nm, although this varies between individuals. The region between 400 and 700 nm is used by plants to drive photosynthesis and is typically referred to as Photosynthetically Active Radiation (PAR).

 

Visible spectrum is divided in various light colors, which effects on chlorophyll, photosynthesis, and plant morphology can be een in the table below (Andersen, Hansen,  1990).

Visible Light Spectrum Effects

Far red light increases total biomass (Lee et al., 2016, Pinho et al., 2017), while at the same time is increasing plant elongation (Stutte et al., 2009) and decreases pigment concentration of plants (Li and Kubota, 2009). As the plant elongation and decrease in pigment concentration are not desirable therefore this biomass increase can not be fully applied. 

Red light benefits reproductive growth (Li et al., 2012), increases tomato yield (Lu et al., 2012), reduces nitrate concentration (Samuoliene et al., 2011) and increases vitamin C concentration (Bliznikas et al., 2012) in plants. As that colour of light is increasing yield by decreasing nitrate content and increasing C-vitamiin content, considering that both factors are highly desirable, then this colour has big potential to use in plant production.

Orange light accelerates growth of transplants (Brazaityte et al., 2009), and therefore this light colour is also desirable in plant production.  

Green light promotes growth (Johkan et al., 2012), reduces nitrate concentration (Samuoliene et al., 2012a) and increases saccharide concentration (Samuoliene et al., 2012a)  of plants. Green light also has positive effect on vitamin C concentration (Samuoliene et al., 2012b) of plants. This colour of light is contributing to only desirable factors in plant production and has also big potential to use in plant production.

Blue light results in compact plants (Sergejeva et al., 2018). Blue light benefits vegetative growth (Li et al., 2012). Blue light increases pigment concentration (Sergejeva et al., 2018) in plants. The concentration of vitamin C is greatest under blue light (Li et al., 2012). This colour of light is contributing to only desirable factors in plant production and has also big potential to use in plant production.

UV light. Like all living organisms, plants sense and respond to UV radiation, both the wavelengths present in sunlight (UV-A and UV-B) and the wavelengths below 280 nm (UV-C). All types of UV radiation are known to damage various plant processes. Such damage can be classified into two categories: damage to DNA (which can cause heritable mutations) and damage to physiological processes (Stapleton, 1992). While UVA light can have also positive effects on plants: UVA light increases anthocyanin concentration in baby leaf lettuce (Li and Kubota, 2009). Therefore tha UV radiation is rarely used in plant production. 

 

Research Findings and the Model

Experimental Setup and Findings. Model is proved by one end – far red. Far red filter filtered out almost all far red light. Plants were grown on open greenhouse bench and under filter.

Plants had significantly lower amount of tirpburn injury on leaves (Table 1), and contained 26% more Ca (Table 2). 

 

Filter	Weight (g)	Height (cm)	Number of leaves
			Total	fresh	tipburn
Filter	34.0	15.4	25.1	21.6	3.5
Control	39.7	18.6	24.5	15.1	9.4
p	0.059	0.011	0.556	<0.001	<0.001

Table 1. The weight (g), height (cm), total number of leaves, the numbers of fresh and injured leaves per plant of lettuce accoding to spectral filters. 

Filter	Dry matter	Chlorophyll	Ca (young leaves)
	%	mg/g fw	g/kg dw
Filter	6.27	3.3	1.21
Control	8.48	4.5	0.89
p	0.114	<0.001	<0.001

Table 2. The content of dry matter (%), Chlorophyll (mg/g fw), Ca (young leaves) (g/kg dw)  in lettuce plants accoding to spectral filters. 

 

The model of light dependent calcium nutrition

At the same time different light spectrums and Calcium nutrition in plants can have interactions proved by me Margit Olle. Margit Olle demonstrated for the first time that lowering the level of far-red light Ca content in lettuce increased and calcium deficiency symptoms decreased. Since 2001, there are no literature evidences, that linkages between all light spectrums Calcium uptake have been revealed. 

Margit Olle propose that there are two assumptions associated with Ca movement in every light spectrum, which together are giving the result. One of those assumptions will be the same for all other light spectrums, while second assumption is light spectrum dependent. As both assumptions for every light spectrum are giving positive results, then the outcome should also be positive. Therefore, Margit Olle could say that we will have novel basic knowledge of the element Calcium, which advances beyond the state of the art, which results in different Ca nutrition under different light spectrums. (Table 3). 

Light spectrum	Calcium content	Reference
Far-red	Far-red ↓ = Ca content ↑	Kleemann, M. (2002), Margit Olle discovery
Red	Red ↓ = Ca content ?	Unknown
Orange	Orange ↓ = Ca content ?	Unknown
Green	Green ↓ = Ca content ?	Unknown
Blue	Blue ↓ = Ca content ?	Unknown
UV light	UV light ↓ = Ca content ?	Unknown

 

Table 3. The model of light dependent Calcium nutrition. The unknown in table is known for Margit Olle, who would like to sell the model. 

 

Reducing far red light in light spectrum increases Ca content in plants, which was proved by Margit (Kleemann, 2002), this was a major discovery in science knowledge, which also had two assumptions, which both gave final positive result. If the optimal lights spectrums to increase Ca content in plants will be revealed as results of the project it is expected to result in improved yield and quality of greenhouse vegetables. 

How does this model work?

Far-red light spectrum (2 positive assumptions) = positive result - discovery.  Margit Olle developed 2 positive assumptions for every light spectrum. It is a mathematical MODEL – scientific knowledge. Two positive assumptions should give a positive result! 

Conclusion

Calcium is an essential mineral macronutrient and is transported into plants with the transpiration stream. Since Ca is not freely mobile in the plant, short periods of Ca-deficit rapidly affect growing tissues. There is no movement of Ca from older to newly developed tissues. Many vegetables develop unique symptoms: for example, black heart in celery, tipburn in lettuce, tipburn in chervil, tipburn of Chinese cabbage and blossom end rot in tomato. The unpredictability of the occurrence of Ca-deficiency and the absence of any effective control procedures makes the problem serious. Many scientists have found that tipburn is a major limitation in production of lettuce. The unpredictability of tipburn occurrence and the absence of totally effective control procedures make the problem very serious. Tipburn is so important due to the facts that this disorder results in tissues collapse on plants and tipburn on lettuce is usually not possible to correct by Ca fertilization and other existing methods. Up to date the best method against tipburn on lettuce is negative DIF and growing plants under far red filter.

• The benefits of increasing calcium content:
  • reduced tipburn losses, 
  • decreased diseases and pest attacks, 
  • improved quality and storability of lettuce.
• The entire model is for sal

The MODEL of light spectrum induced Ca nutrition for the first time globally.

Margit Olle – is the author of 16 books, 15 of them are in English.