Reasons for leaf curling
1.High temperature, drought and water shortage
During the growth process of crops, if they encounter high temperatures (the temperature continues to exceed 35 degrees) or dry weather and cannot replenish water in time, the leaves will roll upward.
During the growth process, due to the large leaf area, the dual effects of high temperature and strong light, the transpiration of the leaves of the crop is enhanced. The rate of water transpiration from the leaves is greater than the rate of water absorption and transport by the roots. This can easily cause the plant to be in a state of water shortage, thus causing the plant to be in a state of water shortage. The stomata of the leaves are forced to close, the surface of the leaves is dehydrated, and the lower leaves of the plant tend to curl upward.
2. Ventilation problem
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 will be relatively strong, which will cause the vegetable leaves in the shed to roll upward. What is particularly obvious during the seedling stage is that the ventilation in the greenhouse is too fast, and the exchange of outdoor cold air and indoor warm air is strong, which can easily cause the vegetable leaves near the vents to curl. This kind of upward rolling of leaves caused by ventilation conditions usually starts from the leaf tip. The leaves become chicken claw-shaped, and in severe cases, the stem tips have white edges.
3. Drug hazard problem
As the temperature rises, especially in summer, the temperature is relatively high. If you are not careful when spraying, phytotoxicity will occur. Once the concentration of the drug is too high, phytotoxicity will occur. The surface of the leaves will change color or have spots, and the leaves will also curl upward. . For example, phytotoxicity caused by improper use of the hormone 2,4-D will cause the leaves or growth points to bend, the new leaves cannot expand normally, the leaf edges are twisted and deformed, the stems and vines are raised, and the color becomes lighter.
4. Excessive fertilization
If crops use too much fertilizer, the concentration of the soil solution in the root system will increase, which will hinder the absorption of water by the roots, causing the leaves to become water-deficient, causing the leaflets to turn and roll up.
For example, when too much ammonium nitrogen fertilizer is applied to the soil, the middle ribs of the leaflets on mature leaves will bulge, the leaflets will show an inverted boat bottom shape, and the leaves will turn up and roll up.
Especially in saline-alkali areas, when the salt concentration of the soil solution is high, it is easier for the leaves to curl upward.
5. Lack of nutrients
When plants are severely deficient in phosphorus, potassium, sulfur, calcium, copper, or some trace elements, leaf curling symptoms can occur. These are physiological leaf curls, which are often distributed on the leaves of the entire plant. They are not accompanied by bright vein mosaic symptoms and often occur on the leaves of the entire plant.
6. Improper field management
When vegetables are topping too early or crops are pruned too early or too heavily. Picking vegetables too early can easily lead to the growth of axillary buds, which will lead to nowhere to transport the phosphoric acid in the vegetable leaves, causing the lower leaves to age first and the leaves to curl. If crops are pruned too early or pruned too heavily, it will not only affect the development of the underground root system and limit the quantity and quality of the root system, but also cause poor growth of the above-ground parts, affect the normal growth and development of the leaves, and induce leaf curling.
7. Disease
Viral diseases are generally spread by aphids, whiteflies, etc. When a virus disease occurs on a plant, all or part of the leaves will curl upward from top to bottom. At the same time, the leaves will become chlorotic, smaller, shrunken, and clustered. In severe cases, there will be only veins but no mesophyll, mostly in the heart leaves. and on the upper leaves.
In the later stages of the onset of leaf mold, the leaves will gradually curl from bottom to top. The leaves in the lower part of the diseased plant will be infected first, and then gradually spread upward, causing the plant leaves to turn yellow-brown and dry. When the disease is severe, the leaves of the entire plant will curl.
Reasons for leaf curling
1. Watering during prolonged drought
If the soil is too dry in the early stage and the amount of watering is suddenly too large in the later stage, the transpiration of the crop leaves will be severely inhibited. When the leaves show a state of self-protection, they will rewind and the leaves will curl downward.
2. Impact of low temperature freezing damage
If the temperature continues to fall below 10°C, the mesophyll cells of crops will be damaged by cold, and the leaves will begin to wilt. In severe cases, the leaves will dry up and bend downward, and the mesophyll cells will freeze and turn white. Late spring cold can also cause new leaves to curl downward!
3. Improper use of hormones
When the concentration of naphthalene acetic acid is too high, the leaves will show a rewinding phenomenon after spraying. When 2,4-D is dipped in flowers, the concentration is too high or it is sprinkled on the leaves, causing the leaves to thicken, shrink or curl downward.
4. Pest harm
The mites are very small and often difficult to identify with the naked eye. The main symptoms of plant damage by mites include narrowing of leaves, stiffness and uprightness, downward shrinkage or distortion, and finally bald tips. The leaves will become smaller, harder and thicker. The most important thing is that the back of the leaves will be oily and have a tea rust color. Aphid damage can also cause severe leaf curling, because aphids generally feed on the underside of leaves and on young tissues, so aphid damage can also cause leaves to curl down to varying degrees.
5. Nematode harm
Infection by nematodes will cause the roots to be unable to absorb nutrients and conduct serious damage to the roots, causing the leaves to turn downwards.
