Why is cucumber easy to burn under low temperature and strong light?

1. Symptoms: There is no necrotic plaque on the edge of cucumber leaves, but chlorotic spots appear on the mesophyll inside the leaf margin. As time goes by, the necrotic plaque gradually enlarges and increases contiguous. Due to the degree of damage and the time of injury, the symptoms are different. Some necrotic spots of the damaged leaves are very fine. Some of the damaged leaves are only the chlorotic and yellowing of the mesophyll between the veins, but they have not reached the level of necrosis. If the adversity continues, this part of the mesophyll will be necrotic, but the mesophyll near the big vein remains green, and the leaves gradually curl down like a parachute. The symptoms of parachute curl often occur in pieces.

2. Etiology analysis: This is a kind of leaf burn caused by intense illumination in a low temperature environment, which is a physiological disease. It occurs mostly in the late autumn and winter of the solar greenhouse and in the middle of the wintering season. The low temperature period from November to March of the next year usually occurs in the middle and upper leaves of the whole greenhouse, and most of the leaves on the south side of the plant are damaged. The part of the blade facing the southeast is seriously affected.

The occurrence of this disease is mostly attributed to the cucumber varieties themselves. Some varieties have poor tolerance to low temperature and are not resistant to glare. This phenomenon occurs when cultivated in low temperature seasons. The authors found that in the same greenhouse, some varieties of leaves were damaged and those with strong resistance were able to grow normally. In addition, some greenhouses with irregular construction, although the film has good light transmission performance, the wall is thin, the rear roof is short and the elevation angle is small, resulting in poor overall insulation performance of the greenhouse, low night temperature, large temperature difference between day and night, especially low soil temperature. Under strong light, the leaves are easily burned.

3. Control measures: select varieties with strong environmental resistance. The author worked in the Daxing Changziying Science and Technology Demonstration Zone in Beijing, and tested more than 20 special varieties of protected areas in the shed. None of this problem occurred. This disease is a chronic stressful physiological disease, and some farmers adopt temporary heating. It is often impossible to solve the fundamental problems, and it takes time and effort, and the people and the people are hurting. Therefore, building a high-standard, high-performance solar greenhouse is the foundation for solving this disease.