The decreased quality of leafy vegetables and tipburn caused by inappropriate light intensity are serious problems faced in plant factories, greatly reducing the economic benefits. The purpose of this study was to comprehensively understand the impact of light intensity on the growth and quality of different crops and to develop precise lighting schemes for specific cultivars. Two lettuce (Lactuca sativa L.) cultivars—Crunchy and Deangelia—and one spinach (Spinacia oleracea L.) cultivar—Shawen—were grown in a plant factory using a light-emitting diode (LED) under intensities of 300, 240, 180, and 120 μmol m⁻² s⁻¹, respectively. Cultivation in a solar greenhouse using only natural light (NL) served as the control. The plant height, number of leaves, and leaf width exhibited the highest values under a light intensity of 300 μmol m⁻² s⁻¹ for Crunchy. The plant width and leaf length of Deangelia exhibited the smallest values under a light intensity of 300 μmol m⁻² s⁻¹. The fresh weight of shoot and root, soluble sugar, soluble protein, and ascorbic acid contents in the three cultivars increased with the increasing light intensity. However, tipburn was observed in Crunchy under 300 μmol m⁻² s⁻¹ light intensity, and in Deangelia under both 300 and 240 μmol m⁻² s⁻¹ light intensities. Shawen spinach exhibited leaf curling under all four light intensities. The light intensities of 240 and 180 μmol m⁻² s⁻¹ were observed to be the most optimum for Crunchy and Deangelia (semi-heading lettuce variety), respectively, which would exhibit relative balance growth and morphogenesis. The lack of healthy leaves in Shawen spinach under all light intensities indicated the need to comprehensively optimize cultivation for Shawen in plant factories to achieve successful cultivation. The results indicated that light intensity is an important factor and should be optimized for specific crop species and cultivars to achieve healthy growth in plant factories.

Light-emitting diodes (LEDs) have been regarded as the best artificial source of light for a plant factory. However, the effect of light quality on seedling production in such environments requires further study. On the basis of the practical application of light on cucumber seedlings (Ansha Company) in plant factories, the present investigation tracked and recorded the specific effects of red and blue light on the growth of the seedlings by analyzing the photo-biological mechanism involved. The growth parameters, as well as the photosynthetic characteristics of cucumber seedlings, were measured at different variations of light quality. The results showed that when the proportion of red light in the light source was higher than blue light, the height of the seedlings, leaf size, stem diameter, Dixon Quality Index (DQI), relative chlorophyll content, and the net photosynthetic rate were higher than those of the experimental group with a relatively high proportion of blue light. In the case of R7B3 (70% red light and 30% blue light), the stem diameter, DQI, and net photosynthetic rate of seedlings were 14%, 57%, and 22% higher than the minimum value, respectively. The present study analyzed the influence of red and blue light on plant growth characteristics during actual production and provides standardization for it.