Amaranth is a vegetable with long sunshine time. Only after vernalization at low temperature can bolting bloom under long sunshine conditions, but it is often not bolting under short sunshine conditions. However, the requirements for sunshine length are different between northern and southern varieties.

The growth and development of leek need moderate intensity of light, but it has strong shade tolerance. When the light is too strong, the growth of stems and leaves is hindered, the cellulose content in leaves increases, the mesophyll tissue is rough and hard, and the product quality decreases. Too weak light weakens photosynthesis and reduces accumulated assimilation products, resulting in thinning of leaves, reduction of tillers, slower growth and lower yield. Under the condition of weak light or no light, leek can be softened and cultivated to produce leek yellow. In leek products, the contents of cellulose, chlorophyll and vitamin C all decreased, while the content of lutein increased. Because the main nutrition of its growth comes from the nutrients stored in the underground short stems, in order to soften the roots of leeks, it must be cultivated first. During the organogenesis of leek, different varieties have different responses to light intensity. The dual-purpose varieties of Chinese chive and Chinese chive introduced from the south are produced in the low light condition in the greenhouse in winter, and their growth speed is fast, which may be related to their different light utilization and adaptability in the process of systematic development.

Prompt board

The suitable light intensity of leek in vegetative growth period is 20,000 ~ 40,000 lux. The upper limit of suitable temperature for photosynthesis is 23℃. The net photosynthetic rate is the same at 5 ~ 23℃. On sunny days, the diurnal variation of net photosynthetic rate of leek showed a double-peak curve, with a peak in the morning and a trough in the afternoon. The main reasons for the decrease of net photosynthetic rate at noon and afternoon are too high leaf temperature, too low air relative humidity and too high stomatal resistance. The net photosynthetic rate of leek leaves is the highest in 18 ~ 25 days after harvest, which can be used as functional leaves to export nutrients. Therefore, from this perspective, the interval between leek harvesting should not be less than 25 days.