How to increase the levels of anthocyanin when growing Purple strains

Many cannabis growers are attracted to the pigments found in cannabis strains, especially those that exhibit purple hues. This article delves into the production of anthocyanin, focusing on how environmental conditions and lighting technologies can be harnessed to improve the aesthetic qualities and phytochemical content of marijuana plants.

It is well known that the appearance of cannabis plants significantly contributes to their appeal among consumers and growers. This is particularly evident in varieties that exhibit a wide spectrum of vivid colours, ranging from deep purple to blue and red, which is what happens with Purple Kush, Gelato-K, or Swiss Dream Rosé Auto CBD. The origin of these tones can be attributed to anthocyanins, a type of water-soluble compounds that belong to the broader category of phenolic phytochemicals known as flavonoids.

These pigments aren’t exclusive to cannabis but are common throughout the plant kingdom, especially in a wide range of fruits and vegetables. The synthesis of these pigments is a strategic adaptive response of plants to various environmental stimuli. They play a vital role in their defence mechanisms, improving resilience against many influences both biotic (pathogenic attacks) and abiotic (drought, lack of nutrients, or excessive exposure to light). Therefore, these pigments provide a very versatile protection to cannabis plants which is driven by several factors.

Environmental and genetic factors

The synthesis of anthocyanins in cannabis is a multifaceted process that depends on several genetic and environmental factors that influence the stability and intensity of these pigments. These factors include pigment structure and concentration, pH levels, temperature, and light intensity and quality, amongst others.

These components interact in a complex and synergistic way to foster an optimal environment that promotes growth. Understanding these mechanisms is crucial for both growing practices and breeding processes used to improve the desired traits in cannabis, including colouring for aesthetic or consumer purposes, as well as to potentially influence the therapeutic properties of the plant.

1- pH levels

The influence of the pH on anthocyanin levels in cannabis plants is crucial to obtain the vibrant purple tones that characterise the Purple varieties. Under acidic conditions (low pH), anthocyanins tend to show red tones, whereas they tend to become bluer under alkaline conditions (high pH). A neutral pH promotes the appearance of purple tones. Adjusting and maintaining the right pH levels is essential not only for the overall health of the plants, but also to maximise the expression of these desired pigments.

For best results, it is advisable to keep the pH of the soil between 5.5 and 6.5, and between 5.8 and 6.3 in hydroponic systems. These optimal conditions promote the absorption of nutrients, while boosting the production of anthocyanins, which results in an intense and attractive colouring with beautiful purple tones.

2- Temperature

Exposure to low temperatures can induce oxidative stress in plants, leading to an increase in the expression of the genes associated with anthocyanin synthesis. The October harvest period for outdoor cannabis serves as an example of this phenomenon. This positive regulation results in a higher accumulation of anthocyanins, which in turn improves the plant’s resistance to low temperatures, working in a similar way to an antifreeze to safeguard cellular integrity. Due to the increased number of anthocyanins produced by the plants, the colouring of their leaves and buds intensifies with shades of purple, red, and blue.

On the contrary, higher temperatures tend to reduce anthocyanin levels, resulting in less vibrant plant pigments. It is important to note that the ability to produce intense colours through increased production of anthocyanins depends on the genetic composition of each cannabis strain: Some varieties are genetically predisposed to produce high levels of anthocyanins, whilst others may show little change in colour under the same conditions.

3- Phytohormones

Beyond environmental stimuli, anthocyanin synthesis is also governed by a number of internal factors, such as plant hormones. These small molecular compounds are crucial for managing various physiological processes within plants, including growth patterns and responses to biotic and abiotic stressors.

Research indicates that plant hormones play an important role in the regulation of the synthesis of anthocyanins, influencing it either positively or negatively. For instance, abscisic acid is known for its role in regulating plant growth, development, and adaptation to stress; and it has been observed to promote the formation of anthocyanins in leaves and various fruits, including apples and sweet berries.

Salicylic acid, another vital hormone, strengthens the plant’s immunity and is associated with increased levels of anthocyanins in grapes or pomegranates. In contrast, it has been found that ethylene, a hormone that’s fundamental in processes such as plant growth, aging, fruit ripening, and adaptation to stress, suppresses anthocyanin levels under certain conditions.

While plant hormones have been shown to trigger or inhibit anthocyanin synthesis in response to stress, the precise molecular mechanisms that govern this regulatory pathway require further research.

4- Nutrients

Anthocyanin concentrations vary significantly depending on genetic composition, mineral content, and nutritional supplementation, which are all crucial for plant growth, tissue repair, reproduction, and overall vitality. Cannabis plants require 17 essential nutrients; and primary macronutrients, such as nitrogen, phosphorus, and potassium, are needed in greater quantities. A deficiency of these nutrients can negatively influence the synthesis of anthocyanins, but research exploring this relationship remains quite scarce.

High levels of anthocyanins are not only indicative of a nitrogen or phosphorus deficiency, as these levels can also derive from several other nutritional imbalances. Some species consistently exhibit these pigments as an inherent feature of their phenotype, regardless of external stressors, whereas others don’t show these colours at any time during their life cycle.

5- Lighting

Light quality, intensity, and duration are major variables in any growing environment which significantly influence epigenetic modifications. The strategic use of different lighting methods can influence the composition of phytochemicals, possibly modifying the way anthocyanins are expressed in later generations.

This underlines the fundamental role of light in modulating plant biochemical pathways and genetic expression, thereby shaping the phenotypic characteristics of cannabis. Different wavelengths of light can promote or inhibit anthocyanin production. Phytochromes and cryptochromes, which are photoreceptors, perceive the red and blue light spectra respectively. This detection initiates the start of the transcription processes that drive the biosynthesis of flavonoids, including anthocyanins.

The resulting anthocyanin pigments bestow plants with a wide variety of beneficial protective attributes, such as anti-oxidation, photoprotection, and heat dissipation capabilities, cooling the plant tissue and maintaining cell integrity.

Conclusion

By understanding the genetic and environmental factors that influence anthocyanin synthesis (including temperature, pH, phytohormones, nutrients, and lighting), growers can employ advanced techniques to improve these traits. The manipulation of these elements can result in cannabis strains with unique pigments and therapeutic properties, which in turn presents exciting opportunities for the development of new cannabis genetics that will satisfy the needs of both growers and consumers.