Chlorosis: A deficiency of chlorophyll (natural compound present in green plants that gives them their color) causes chlorosis, a yellowing of leaf tissue. Poor drainage, damaged roots, compacted roots, high alkalinity, and nutrient shortages in the plant are all possible causes of chlorosis. Nutrient deficits can result from a lack of nutrients in the soil or from the nutrients being inaccessible due to a high pH (alkaline soil). Injured roots or insufficient root growth may prevent nutrients from being absorbed.
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Chlorosis
Chlorosis is caused due to deficiency of certain elements like Iron, Sulphur, Nitrogen, Mg+2, Potassium, Manganese, etc. when the plants are grown in the light. The word chlorosis is derived from the Greek word khloros meaning “greenish-yellow“, “pale green“, “pale“, “pallid“, or “fresh“.
Chlorosis Meaning in Hindi
Chlorosis = क्लोरोसिस, हरिद्रोग, हरिमाहीनता, हरित-रोग, हरितरोग, अहरितता
Dictionary Meaning:-
Botany: Loss of the normal green coloration of leaves of plants, caused by iron deficiency in lime-rich soils, disease, or lack of light.
Medicine: Anaemia caused by iron deficiency, especially in adolescent girls, causing a pale, faintly greenish complexion.
Causes of Chlorosis?
Causes of Chlorosis occurs due to the plant leaves don’t have enough nutrients to synthesise all the chlorophyll they have, needs to processing. However, the exact conditions vary from plant type to plant type but the listed factors affects in the chlorosis by reduction in chlorophyll during the growing season, due to reduction in:
In Minerals;
- Iron, Magnesium, or Zinc – The specific mineral deficiency in the soil.
- The deficiency of proteins and nitrogen.
- exposure to sulphur dioxide.
- Interveinal Chlorosis that causes leaves to yellow while its veins remain green.
- Mobility of Magnesium in plants is necessary as per requirement in chlorophyll, and deficiency of it, chlorosis manifests in older leaves first, due to chlorophyll in older leaves, switch down and transports to new leaves.
In Root:
- a soil pH at which minerals become unavailable for absorption by the roots.
- poor drainage (waterlogged roots).
- damaged and/or compacted roots.
In Pathogens:
- presence of any number of bacterial pathogens, for instance Pseudomonas syringae, tagetis that causes complete chlorosis on Asteraceae
- fungal infection, e.g. Bakanae.
And Others:
- pesticides and particularly herbicides may cause chlorosis, both to target weeds and occasionally to the crop being treated.
- exposure to sulphur dioxide.
- ozone injury to sensitive plants.
What is Iron Chlorosis?
The growth and development of a plant depends on chlorophyll, any reduction in chlorophyll during the growing season can reduce plant growth and vigor, and if it contains iron deficiency, affects the plant by yellowing of her leaves, due to the deficiency of Iron content, creating chlorosis in leaves called Iron chlorosis, in many desirable plants.
Primary symptom: Interveinal chlorosis.
[Interveinal chlorosis: The development of a yellow leaf with a network of dark green veins]
In severe symptom(s): The entire leaf turns yellow or white and the outer edges may scorch and to continue with it, the plant cells die when leaves turn brown. It’s common for an individual branch or one half of a tree to be chlorotic while the remaining tree appears to be normal.
In some cases, the entire landscape may be affected due to chlorosis in the vegetation of an area while in others only the most susceptible plants show deficiency symptoms.
Chlorophyll, the green pigment responsible for photosynthesis (food processing/sugar production) in a plant, the lack of chlorophyll indicates yellow leaves i.e, chlorosis.
During the growing season, the reduction of chlorophyll in a plant can reduce plant growth and vigor. On result, chlorotic plants often produce smaller fruits, poor in quality sometimes with unusual (bitter) flavour of fruit too.
In severe cases, or if iron chlorosis persists over several years, individual limbs or the entire plant may die.
Read More: 17 Nutrients and Role of Manures and Fertilizers | Plant Nutrients in the Soil |
Causes of Iron Chlorosis?
Iron chlorosis, the causes of it’s, is very complex and not entirely understood. Due to soil complexity so many reactions governs iron availability and make iron chemistry in photosynthesis processing. Iron chlorosis frequently occurs in soils that are alkaline (pH greater than 7.0) and that contain lime; as per conditions that are common in an area.
Even though there typically is plenty of iron in these soils, the high soil pH causes chemical reactions that make the iron solid and unavailable to plant roots. Such iron content will tied up indefinitely unless soil conditions change.
Iron deficiency and chlorosis is aggravated by cool soil temperatures and conditions that restrict air movement into soil: plastic sheet mulching, compaction, and water-saturated conditions. Chlorosis is often more severe where topsoil has been removed exposing lime enriched subsoil.
Examples are eroded soils or soils subjected to land leveling for new housing developments.
Plants that are native to high pH (alkaline) soils usually don’t suffer from iron chlorosis, because they tends to be very efficient in their use of iron or they can obtain more iron from the soil than non-native or poorly adapted plants. Sometimes plants grown in high pH soils may show iron chlorosis due to poor availability of other minerals, particularly manganese.
Treatments
The specific mineral/nutrient deficiency in the soil (often aggravated by high soil pH) may be corrected by the addition of supplements/compounds in various combinations of:
- Iron, in the form of a Chelate
- Sulphur (in the form of Sulphate)
- Magnesium or
- Nitrogen compounds.
Etiolation
Etiolation is caused in green plants when they are grown in dark. Mineral deficiency is not involved in such plants.
Differences Between Chlorosis and Etiolation
CHLOROSIS | ETIOLATION |
| 1. Chlorosis is caused due to deficiency of certain elements like iron, Sulphur, Nitrogen, Mg+2, Potassium, Manganese, etc. when the plants are grown in the light. | 1. Etiolation is caused in green plants when they are grown in dark. Mineral deficiency is not involved in such plants. |
| 2. It is a physiological disease. | 2. It is a physiological phenomenon. |
| 3. During chlorosis, the leaves become non-green even in presence of all other accessory pigments like xanthophyll and carotenoids, etc. | 3. During Etiolation the stem becomes elongated, the leaves become colorless or yellow, young leaves remain unexpanded. Pigments involved in photosynthesis are not synthesized. |
| 4. It may be complete or inter- venial chlorosis. | 4. The absence of light is the only factor in Etiolation and mostly the entire leaf becomes colourless or yellow. |
| 5. Chlorosis can be overcome by supplying the deficient element through any method. | 5. Etiolation can be avoided if the plant is kept in proper sunlight. |
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Source: Koenig, Rich and Kuhns, Mike: Control of Iron Chlorosis in Ornamental and Crop Plants | Greenwaybiotech |