When the crop is affected by adversity, the first manifestation is the leaf, often there will be leaf yellowing, spots, leaf curls and other phenomena, leaf curl leaves have upward roll and downward roll two, only to understand what causes they are, can be targeted to solve.
Blade rolling up cause
1. High temperature, drought and water shortage
When crops encounter high temperatures (temperatures lasting more than 35 degrees) and dry weather during the growth process and cannot replenish water in time, the leaves will roll upwards.
In the growth process, due to the large leaf area, high temperature and strong light double action of the crop leaf transpiration is strengthened, the speed of leaf transpiration water is greater than the speed of water absorption and transport of the root system, so it is very easy to cause the plant to be in a state of water shortage, so that the leaf stomata are forced to close, the leaf surface is dehydrated, and the lower leaves of the plant are easy to roll upwards.
2. Ventilation problems
When the temperature difference between the inside and outside of the shed is large, if the wind is suddenly released, the exchange of cold and warm air inside and outside the shed is relatively strong, which will cause the vegetable leaves in the shed to roll upwards. During the seedling period, it is particularly obvious that the air in the shed is too urgent, and the outdoor cold air and the indoor warm air exchange strongly, which is very easy to cause the vegetable leaves near the vent to curl. This kind of upward rolling of leaves caused by ventilation conditions generally begins to roll from the tip of the leaf, and the leaves are chicken claw-shaped, and in severe cases, the dry tip has a white edge.
3. Drug damage problem
With the temperature rise, especially in the summer, the temperature is relatively high, spraying a little inattention will occur, once the drug concentration is too large, the occurrence of drug damage, the surface of the leaf will change color or long spots, and the leaf will also curl upwards. For example, the improper use of hormones 2,4-d will cause the leaves or growth points to bend, the new leaves cannot be unfolded normally, the leaf edges are twisted and deformed, the stems are raised, and the color becomes lighter.
4. Excessive fertilization
If the amount of fertilizer used by crops is too much, it will lead to an increase in the concentration of root soil solution, which will hinder the absorption of water by the roots, so that the leaves will realize the phenomenon of water shortage, causing the leaflets to flip and roll up.
For example, when too much ammonium nitrogen fertilizer is applied in the soil, the midrib of the small leaves on the mature leaves is raised, the leaflets show a reversed bottom shape, and the leaves are turned up and rolled up.
Especially in saline-alkali areas, when the salt concentration of the soil solution is high, it is also more likely that the leaves will curl upwards.
5. Deficiency of hormones
When the plant is seriously deficient in phosphorus, potassium, sulfur, calcium, copper, and some trace elements, it can cause leaf curl symptoms. These are physiological curls, often distributed on the leaves of the entire plant, without the symptoms of bright veined flowers, and often occur on the leaves of the entire plant.
6. Improper field management
When vegetables are picked too early or when the whole crop is pruned too early or too heavy. Vegetable topping is too early, which is easy to breed axillary buds, resulting in nowhere to transport phosphoric acid in vegetable leaves, resulting in the lower leaves aging first, and the leaves appear to shrink. If the crop is beaten prematurely and pruned too heavily, it will not only affect the development of the underground root system, limit the quantity and quality of the root system, but also make the aboveground part of the growth poor, affect the normal growth and development of the leaves, and induce curly leaves.
7. Disease
Viral diseases can generally be transmitted through aphids, whiteflies, etc. When the plant has viral disease, all or part of the leaves will be bent upwards from top to bottom, and the leaves will fade green, become smaller, shrink, clump, clump and other phenomena, and in severe cases, there are only leaf veins and no leaf flesh, which are mostly manifested in the heart leaf and the upper leaf.
In the later stage of leaf mold disease, the leaves will gradually curl from the bottom up, and the leaves in the lower part of the diseased plant will first occur, and then gradually spread upwards, so that the leaves of the plant will be yellow-brown and dry, and the leaves of the whole plant can be curly when the disease is serious.
Blade rolling down cause
1. Water for a long time
If the soil is too dry in the early stage, and the watering volume is too large in the later stage, the transpiration of the crop leaves will be seriously inhibited, and when the leaves show a self-protective state, they will be rewinded, and the leaves will be rolled downwards.
2. Low temperature frost damage effect
If the temperature continues to be below 10 °C, the mesophyll cells of the crop will be affected by cold, the leaves will begin to wilt, and in severe cases, the leaves will dry up and bend downwards, and the mesophyll cells will freeze and bleach. Cold spring can also cause the new shoots to curl downwards!
3. Improper use of hormones
When the concentration of naphthaleneacetic acid is too large, the leaves will show a reverse winding phenomenon after spraying, and when the flowers are dipped in 2,4-d, the concentration is too large or sprinkled on the leaves, making the leaves thicker, wrinkled or rolled downward.
4. Pest hazards
The tea yellow mite is actively small and is often difficult to recognize with the naked eye. The main symptoms of plant infestation are narrowing, stiff and erect leaves, downward creases or twisted deformities, and finally baldness. The leaves will become smaller, harder and thicker, most notably oil-stained on the back of the leaves, with a brown rust color. Aphid infestation can also cause severe leaf curls, because aphid habits generally feed on the back of the leaf and on the young tissues, so aphid infestation will also cause the leaves to roll down to varying degrees.
5. Nematode hazards
The infestation of nematodes can cause the roots to absorb nutrients and conduct poorly, and serious lesions appear in the roots, causing the leaves to flip downwards.
(Part of the content source and Rising Sun Agricultural Technology, creator: plant protection home, if you need to reprint please indicate!) ）