Why does the seedling turn yellow? This is a sign that something is missing for her

A key component of any plant is chlorophyll. Thanks to it, a vital link between the sun and the biosphere is realized: chlorophyll, contained in plant cells, under the action of sunlight synthesizes organic substances from water and carbon dioxide. Yellowing of plants indicates a violation of the formation in them of chlorophyll - a disease called chlorosis. So the answer to the question of why the tomato is turning yellow is quite simple. But this alone is not enough - we have to get to the reasons. There are several of them.

The most common of these is a malnutrition of the root system. This is due to its damage, physical or temperature (hypothermia). But if the temperature regime is violated, chlorosis is reflected on the whole plant. And if, say, the mechanical damage to the root system was caused by the planting of tomato seedlings on a bed, only the lower leaves turn yellow. In this case, it is necessary to wait for rooting of seedlings and the appearance of new accessory roots - the tomato will cope with chlorosis independently.

To determine the cause of chlorosis, it is enough to look closely at the leaves of a young plant. And if the tomato seedlings turn yellow from the older (lower) leaves, one should also suspect a shortage of one of the chemical elements important for the tomato.
Most often chlorosis of tomato seedlings indicates a nitrogen deficiency. About it, and leaf veins are bluish-red, and small leaves on the whole plant as a whole. Lower leaves after yellowing die. If the seedlings are grown for sale, you can not even try to take it to the market: obvious signs of chlorosis will scare off the buyers, and no explanation of why the tomato seedling turns yellow will not help.

Yellowing can also cause potassium deficiency, but here the process often goes too far due to the accumulation of ammonia nitrogen, accompanied by dehydration of leaves and their twisting, until the appearance of signs of tissue necrosis.
The next reason why the tomato seedling turns yellow is zinc deficiency. He gives himself out also with small numerous speckles of yellow color on young leaves. They are also abnormally small, they can be entirely yellow, sometimes twisting upward. Necrosis of tissues, unlike potassium deficiency, manifests itself immediately over the entire surface of the leaf, but passes much faster.

If the chlorosis of young leaves of seedlings starts from their base, and the color from yellow-green through lemon-yellow becomes yellow-white, then the plant reacts to iron deficiency. It is reflected only on young leaves, not passing to the older ones. This kind of deficiency can happen at an early stage of growing seedlings, if its round-the-clock illumination is not supported by top-dressing with iron content. It is only necessary to resume them, as the plant comes to a normal state in just a few hours.

But the deficit of trace elements and nutrients is relatively easy to correct. It is quite another matter when the answer to the question of why the tomato is turning yellow is the following: it is fusariosis. This dangerous fungal disease can affect tomatoes at any age. It is also difficult to fight against it because the disease can be discovered too late. Prevention is the most effective way of fusarium wilt . But if the seedlings are already affected, immediately isolate healthy plants from the diseased; The first to treat the drug, the second - immediately destroy (burn).