Chlorosis is different, or What is missing in our plants?
This year I often observed the picture: among the sumptuous green crowns of trees and shrubs, here and there, like candles, the “lit” tops of shoots “burn”. This is chlorosis. Most of us have known about chlorosis since our school biology classes. I remember that this is a lack of iron ... But chlorosis is an ambiguous concept. And not always highlighting the foliage means a lack of iron. What is chlorosis, what is lacking for our plants in chlorosis and how to provide them with competent help, we will tell in the article.
What is chlorosis?
Chlorosis at its core is an external manifestation of signs indicating that the plant is inhibited, that the formation of chlorophyll in its tissues is slowed down and, as a result, the activity of photosynthesis is reduced. This can be a highlighting of the leaf plate between the veins, along with the veins, along the edge, spots or over the entire surface, i.e., a change in its color from normal to light green, yellow, cream.
At the same time, the leaves can lose their color both from the petiole to the tip, and from the edge of the leaf blade to the petiole, starting from the top of the shoot, from the center or from the bottom. It is important to observe these additional characteristics when determining the problem, since it is they and some others, which will be discussed later, that suggest the cause of chlorosis. And he has many reasons.
The name "chlorosis" comes from the Latin word chlorosis – chlorophyll.
Types of Chlorosis
Despite the fact that chlorosis, at first glance, has a general concept, science divides this phenomenon into several types:
- non-infectious chlorosis,
- infectious chlorosis
- edaphic chlorosis.
Each of them has similar external manifestations, but a different reason, from which the measures to combat this disease vary.
The most common non-infectious chlorosis is caused by a lack of any element in the plant’s nutrition: sulfur, zinc, calcium, potassium, magnesium. And most often it is carbonate chlorosis (calcareous, or iron), resulting from iron deficiency.
The most common cause of iron chlorosis is an excess of lime in the soil, giving it an alkaline reaction (pH = 7 or more), which keeps iron in a form inaccessible to plants. It occurs quite often, since carbonate soils are quite widespread.
The first symptoms of iron chlorosis appear on plants in spring or early summer, when foliage is highlighted on the tops of the shoots, while the leaf veins remain green. The provocateur of this phenomenon is usually cold rainy weather, enhancing the alkaline reaction of the soil (waterlogging, cold soil).
With prolonged iron deficiency, young leaves stop growing, and after them, the old ones gradually lose their color. If the problem is not solved, the chlorous leaves dry up, crumble, the tops of the shoots die off.
Additional signs of iron deficiency are:
- insufficient maturation of wood (decrease in frost resistance);
- shedding of fruit;
- development of short knots.
Iron chlorosis is also manifested in vegetable crops. In tomatoes, mainly on the upper leaves, inflorescences grow small, the bushes often die. Beetroot has old foliage small, hard, and young light with a burn of tips, woody roots. In cabbage, old leaves are highlighted, young ones do not grow, head of cabbage does not ripen, has a bitter taste. In potatoes, old leaves lose their color, take the appearance of scorched and dry.
Manganese deficiency is found on carbonate and acidic calcareous soils. However, with a slight deficit, the color of the leaves does not change, only with severe insufficiency. Chlorotic spots of various shades appear, located between the veins. Plant growth is inhibited, while the upper bud does not die.
In addition to trees and shrubs, the so-called indicator vegetable plants react to the deficiency of this element with chlorosis. In cucumbers, young leaves grow light green with a yellow border, and dotted necrotic spots are scattered on the leaf blade. In tomatoes, the foliage of the middle tier turns yellow, starting from sites remote from the central vein, discolored areas die off. In the potato, the upper leaves are highlighted between the veins, and dotted necrotic spots are scattered on the chlorotic tissue.
Magnesium deficiency appears on the lower old foliage. Leaf blades do not lose their color evenly, but between the main veins, starting from the edge of the leaf. Sometimes the color changes to red or orange. In the same direction, or from the middle of the macula, necrosis also begins. It is not necessary that these symptoms will appear on all branches, and even more so on all plants.
Additional signs of a lack of magnesium are:
- weakening plant growth;
- smaller size and less intense color of the fruit;
- earlier ripening of the crop;
- decrease in frost resistance.
With sulfur deficiency, the upper, young leaves change color. The veins are highlighted first, and then the tissue of the leaf plate. Often the sheet becomes white with a reddish tint. Plants stop in development, become more susceptible to lack of moisture, to diseases, low temperatures.
With sulfur chlorosis, nitrates accumulate in plant tissues.
Calcium deficiency is also manifested by chlorosis. At the tips of the shoots, the leaves become yellow-green with yellow-brown spots, the edges of the leaf blades are serrated. If a calcium deficiency is observed for too long, a slowdown and gradual death of the root system occurs. In rare cases, necrotic ring spotting appears on the cortex.
Additional signs of calcium deficiency are:
- chopping fruits, a tendency to crack, tan;
- earlier ripening of the crop;
- increased susceptibility to vitreous flesh, internal decay - reduced shelf life.
Attention! Deficiency of trace elements (iron, manganese) is manifested on young foliage, a lack of macrocells (calcium, magnesium, potassium, sulfur) - on old leaves.
Initially, nitrogen deficiency appears on the lower old leaves in the form of uniform lightening (of both the veins and the tissue of the leaf plate). First, the leaves acquire a light green hue, then yellow-green, and with a severe lack of nitrogen, the whole plant loses a healthy color. The volume of the root system is reduced. Short stature is observed, the stems grow hard, thin.
With chronic shortage, the leaf is small, the upper leaves are inclined at an acute angle with respect to the stem. Flowering begins early, but the flowers are small, few in number. Often there is a shedding of both color and ovary.
Additional signs of nitrogen deficiency are:
- early yellowing or redness of the leaf apparatus;
- staining of petioles of leaves in a red-brown shade;
- early ripening of the crop;
- the fruits are brighter in color, but smaller than the grade, tasteless.
Most often, this chlorosis manifests itself on excessively acidic soils, or during periods of prolonged spring rains, when nitrogen is washed out of the root zone. In the latter case, there is no need to deal with nitrogen deficiency since, when sunny warm weather is established, its content indicators return to normal and the plant is restored.
Another reason could be a prolonged drought, which provokes the death of microorganisms that convert nitrogen into a form accessible to plants. In this case, it is necessary to establish watering, and the problem disappears.
An excess of nitrogen leads to zinc deficiency. It appears on old foliage in the form of specks of yellow, orange or red. It occurs in the spring.
With a lack of potassium, chlorosis appears on old leaves in the form of spots on the edges and between the veins. Pale leaves often curl upward. Gradually, edge necrosis appears. There is a slowdown in plant growth, drying out of young shoots.
If potassium deficiency is acute, necrosis can cover the entire leaf blade. Shoots grow short, thin. Plants become unstable to drought and freezing. In addition, the fruits on them grow small, stain poorly, peeling is observed on the grapes, and later - cracking of berries.
There is a lack of potassium in areas with frequent rains and on sandy soils.
Infectious chlorosis occurs due to infection of plants with a virus from the group of NEPO viruses. It is carried by insects. As in previous cases, it begins to appear in spring, but already in the form of lightening of leaves along with veins, yellow spots or stripes along the veins. At the same time, a short knot is observed on the shoots, and fringing on the affected foliage. With the advent of summer, the leaves turn green, but the affected areas remain chlorotic.
Unfortunately, viral diseases are not treated today. The only control measure is the preventive treatment of plants against virus insect vectors.
Edaphic chlorosis occurs as a result of external adverse factors affecting the plant: a sharp deterioration in weather conditions, a sharp change in the chemical composition of the soil, temperature spikes over a wide range, excess or severe lack of moisture ... And also due to poor survival of the scion for stock.
Ways to combat non-infectious chlorosis
Determining the cause of chlorosis, it is impossible to consider only the external signs of the disease. For a more accurate diagnosis, a set of symptoms is required, including the nature of the lightening of the foliage, the full development of new shoots, the “behavior” of old leaves, the quality of the crop, as well as the analysis of the time and place of occurrence of these manifestations associated with the period of the year, weather conditions, and soil quality.
There are different ways to combat non-infectious chlorosis. Here are those that are suitable for any of its type:
- improvement of air and water permeability of heavy soils;
- mulching, in order to preserve moisture in the near-stem circle;
- refusal to use manure on carbonate soils, since carbon dioxide is released during its decomposition, which contributes to the dissolution of lime, which means increased soil carbonization;
- if necessary, regular use of fertilizers containing boron, phosphorus, potassium, iron, manganese, zinc;
- organization of uniform moderate watering;
- selection of chlorine resistant varieties.
With a lack of iron recommended:
- processing sheet apparatus with iron salts;
- foliar top dressing with drugs that include iron chelate;
- top dressing under the root with iron sulfate.
With a lack of magnesium You can use magnesium sulfate, kalimagnesia, ash, dolomite flour.
From zinc chlorosis zinc sulfate, zinc oxide and superphosphate with zinc are used.
Lack of sulfur make up with complex fertilizers - azophos with sulfur, kalimagnesia, diammophos with sulfur.
To make up lack of nitrogen make nitrogen fertilizers - ammonium nitrate, ammonium sulfate, calcium nitrate, urea.
If it is impossible to determine exactly which element is missing, you can feed the plants with any complex fertilizer containing all the necessary substances (Kemira Lux, Uniflor Micro, Universal, etc.).