Anthocyanosis It is a physiological phenomenon that affects plants and manifests itself mainly as a discoloration on leaves, with the appearance of reddish, violet or bluish tones. It is often confused with other plant pathologies, but its origin is in the anthocyanin imbalance, essential compounds that determine the color of flowers, leaves, and fruits. Understanding how and why anthocyanosis occurs is key to caring for our crops and gardens, anticipating its symptoms, and knowing how to prevent or reverse its effects.
What is anthocyanosis and how does it occur in plants?
La anthocyanosis It is the manifestation of the excessive accumulation of anthocyanins in plant tissues, especially in the leaves, although it can also be observed in stems, flowers and fruits. anthocyanins They are pigments from the flavonoid group responsible for giving intense and varied colors, from red and purple to blue depending on chemical and environmental factors.
This process can be activated by various causes related to the environmental stress: low temperatures, nutrient deficiencies (especially phosphorus and potassium), lack or excess of sunlight, drought, mechanical damage, or even water imbalances. When faced with these factors, plants generate more anthocyanins as a defensive mechanism, resulting in anthocyanosis and, consequently, abnormal tissue coloration.
Function of anthocyanins and their vital role in plant health
Beyond the coloring, Anthocyanins play a crucial role in plant physiologyThese pigments:
- They protect against UV radiation, absorbing excess light and preventing cellular damage.
- They have an important antioxidant function, neutralizing free radicals generated by environmental stress.
- They make it difficult for herbivores to attack. and pathogens, making the plant less palatable or more resistant.
- They favor the Pollinator attraction thanks to the intense colors of flowers and fruits.
Anthocyanins are not distributed equally: their presence is most prominent in young leaves, dark fruits, and brightly colored flowers. Under optimal conditions, plants naturally regulate the synthesis and accumulation of these compounds, but any alteration can lead to anthocyanosis.
Types of anthocyanidins and their impact on coloration
The anthocyanidins They are the basic forms (aglycones) of anthocyanins, and each one determines specific nuances:
- Cyanidin: pigment that generates reddish and violet tones, very common in blueberries and cherries.
- Delphinidin: responsible for the bluish tones, common in berries and certain flowers.
- Malvidina: gives intense purple colors, present in red grapes and ornamental vines.
- Pelargonidin: salmon or orange pigment, found in pelargoniums and dahlias.
- Peonidin, petunidin, aurantinidin, capensinidin, rosinidine: They provide intermediate or complementary tones, depending on the species and environmental conditions.
The "batochromic" effect, described by scientist Richard Willstätter, explains how these pigments change color depending on the pH of the environment: In acidic environments, reddish tones predominate, in neutral environments, violets, and blues in alkaline environments. Thus, anthocyanosis can have different visual manifestations depending on the soil and the internal physiology of the plant.
| Anthocyanidins | R1 | R2 | R3 | R4 | R5 | R6 | R7 |
| Aurantinidine | -H | -OH | -H | -OH | -OH | -OH | -OH |
| Capensinidine | -OCH3 | -OH | -OCH3 | -OH | -OCH3 | -H | -OH |
| Cyanidin | -OH | -OH | -H | -OH | -OH | -H | -OH |
| Delphinidin | -OH | -OH | -OH | -OH | -OH | -H | -OH |
| Europinidine | -OCH3 | -OH | -OH | -OH | -OCH3 | -H | -OH |
| Luteolinidin | -OH | -OH | -H | -H | -OH | -H | -OH |
| Pelargonidin | -H | -OH | -H | -OH | -OH | -H | -OH |
| Malvidina | -OCH3 | -OH | -OCH3 | -OH | -OH | -H | -OH |
| Peonidin | -OCH3 | -OH | -H | -OH | -OH | -H | -OH |
| Petunidin | -OH | -OH | -OCH3 | -OH | -OH | -H | -OH |
| Rosinidine | -OCH3 | -OH | -H | -OH | -OH | -H | -OCH3 |
Plant species and families most sensitive to anthocyanosis
La anthocyanosis It can affect a wide variety of plants. Among the most susceptible species and families are:
- Avena sativa (ornamental oats), whose sensitivity results in rapid discoloration under cold or nutrient deficiency.
- Fruits rich in dark colors such as blueberries, cherries, blackberries, grapes, plums and wild berries, where the accumulation of anthocyanins is part of both natural processes (ripening) and responses to stress.
- Brightly colored ornamental plants, such as Pelargonium, Dahlia, Papaver and species from families such as Araceae, Bromeliaceae, Marantaceae, Liliaceae and Euphorbiaceae.
- Trees like Acer (red maple) and Quercus coccinea (scarlet oak), which exhibit intense chromatic changes in the foliage, especially in autumn.
In all of them, anthocyanosis can appear due to external factors, such as low temperatures, light variations, water stress, nutrient deficiencies (mainly phosphorus and potassium) and changes in soil pH.
| Species | Anthocyanin content |
|---|---|
| Euterpe oleracea | 320 |
| Ribes nigrum | 165-412 |
| Aronia melanocarpa | 1480 |
| Solanum melongena | 750 |
| orange | ~ 200 |
| rubus fruticosus | 317 |
| rubus occidentalis | 589 |
| Rubus idaeus | 365 |
| Vaccinium | 558 |
| Prunus | 350-400 |
| (Grossulariaceae). | 80-420 |
| Red grape | 888 |
| Red wine | 24-35 |
| purple corn | 1642 |
Symptoms and diagnosis: differential identification of anthocyanosis
Symptoms of anthocyanosis vary by species and environmental conditions, but common signs include:
- Progressive discoloration of leaves, stems or flowers, with the appearance of reddish, purple or bluish tones.
- Presence of spots or uneven areas colored, mainly on young leaves or leaf margins.
- Sometimes growth reduction and weakening, since excess pigments can interfere with photosynthesis.
It is important to make a differential diagnosis Regarding other leaf spots and discolorations, since diseases such as anthracnose, septoria, iron chlorosis, downy mildew, or powdery mildew infections can cause similar symptoms. To do this, it is recommended to observe:
- Distribution and progression of coloration: Anthocyanosis usually has a more uniform pattern or is associated with environmental stress, while infectious diseases tend to create more localized spots and evolve differently.
- Relationship with external conditions: The appearance of anthocyanosis, especially after temperature changes, drought or nutritional deficiency, is a key indication.
Factors that trigger anthocyanosis
Among the main causes, the following stand out:
- Low or freezing temperatures: cause the accumulation of anthocyanins in the leaves and young shoots.
- nutrient deficit: mainly phosphorus and potassium, but also nitrogen and magnesium to a lesser extent.
- pH fluctuations of the soil: they affect the availability of minerals and modify the chromatic expression of the pigments.
- Water stress: both drought and waterlogging of the substrate affect plant metabolism.
- Exposure to insufficient or excessive sunlight.
- Mechanical damage or insect attacks: stimulate defensive responses that may include the synthesis of anthocyanins.
Relationship between anthocyanins, antioxidants and plant defense
The anthocyanins They are not only visually important: they act as antioxidants and plant immune system modulatorsThey help plants resist oxidative damage, UV radiation, and infections. Several studies have also linked the consumption of anthocyanin-rich fruits with improvements in human health, such as cardiovascular and neurological protection, a strengthened immune system, and a reduced risk of obesity and diabetes. However, in plants, their primary function is protection against stress.
To prevent, correct and manage anthocyanosis in plants it is essential:
- Provide optimal growing conditions: ensure sufficient sunlight (avoiding excess in sensitive species), regular watering, and controlled temperature.
- Balance the substrate: maintain a moderate pH and provide essential nutrients (special attention to phosphorus, potassium and iron).
- Prevent water stress: avoid prolonged droughts or flooding.
- Carry out phytosanitary control: protect plants from pests and diseases that can trigger inappropriate defensive responses.
- Monitor the evolution of symptoms: Act quickly if an unusual color change occurs in young leaves, adjusting the fertilization and environmental conditions.
- In case of established anthocyanosis, apply phosphorus and potassium supplements, adjust the pH (if necessary) and remove the most damaged parts if they present severe necrosis.
Anthocyanosis can be reversed if the causes are identified early and ideal conditions for the species are restored. In many cases, it is also a sign that the plant is activating its defenses, so proper management will allow for its recovery.
Maintaining nutrition, irrigation, and environmental exposure, as well as continuously monitoring leaf changes, will optimize plant health and reduce the incidence of this striking and sometimes alarming phenomenon.