Light should be paid attention to in haze weather of glass greenhouse. Plants in the greenhouse often suffer from weak light barrier (referred to as "weak light disease") due to insufficient light. Their general symptoms are: poor plant growth and thin and soft stems; The leaves are thin, light in color and easy to yellowing; Poor flower bud differentiation, flower organ deformity, serious flower and fruit drop; The fruit grows slowly, with light color, astringent taste and poor coloring. Weak light barrier has a certain impact on the yield and quality of vegetables.

The main countermeasures are to improve the lighting conditions in the glass greenhouse as much as possible. During colonization, appropriately increase the row spacing between plants and reduce the shading between plants; Keep the shed membrane clean to prevent water droplets and dust from adhering to the membrane surface; When the external temperature reaches 15 ℃ in the middle and late stage of vegetable growth and around noon, properly uncover part of the shed film and let the sun shine directly into the shed. In addition, according to the experiment, the polyester aluminized film is spliced into a 2m wide and 3M long reflective screen, which is hung on the upper end of the rear column of the plastic greenhouse (or greenhouse) and the lower side is perpendicular to the ground. It can increase the ground light by 40 ~ 43%, the greenhouse temperature by 3 ~ 4 ℃, the ground temperature by 1.8 ~ 2.9 ℃, the tomato yield by 41.8 ~ 58.1%, and improve the fruit quality; Laying Silver Ash film or aluminum foil on the ground can also increase the light intensity between plants, make the fruit colored well, and prevent the premature senescence of lower leaves.