In general, increasing the fraction of blue light in white light can shorten internodes, reduce leaf area, reduce relative growth rates, and increase nitrogen/carbon (N/C) ratios.
High plant chlorophyll synthesis and chloroplast formation and positive chloroplasts with high chlorophyll a/b ratio and low carotenoid levels require blue light. Under the red light, the photosynthesis rate of the algae cells gradually decreased, and the photosynthetic rate rapidly recovered after going to blue light or adding some blue light under continuous red light. When dark-growing tobacco cells are transferred to continuous blue light for 3 days, ribulose bisphosphate carboxylase/oxygenase (rubulose-1, 5-bisphosphate)
Carboxylase/oxygenase, Rubisco) The total amount and chlorophyll content increased dramatically. Consistent with this, the dry weight of the cells in the volume of the unit culture solution also increased sharply, while it increased slightly slowly under continuous red light.
Obviously, for photosynthesis and growth and development of plants, only red light is not enough. Wheat can complete its life cycle under a single red LEDs source, but to obtain tall plants and large numbers of seeds, an appropriate amount of blue light must be added (Table 1). The yield of lettuce, spinach and radish grown under a single red light was lower than that of the plants grown under the combination of red and blue, while the yield of plants grown under the combination of red and blue with appropriate blue light was comparable to that of plants grown under cool white fluorescent lamps. Similarly, Arabidopsis thaliana can produce seeds under a single red light, but it grows under the combination of red and blue light as the proportion of blue light decreases (10% to 1%) compared to plants grown under cool white fluorescent lamps. Plant bolting, flowering and results were delayed. However, the seed yield of plants grown under a combination of red and blue light containing 10% blue light was only half that of plants grown under cool white fluorescent lamps. Excessive blue light inhibits plant growth, shortened internodes, reduced branching, reduced leaf area, and reduced total dry weight. Plants have significant species differences in the need for blue light.
It should be noted that although some studies using different types of light sources have shown that differences in plant morphology and growth are related to differences in the proportion of blue light in the spectrum, the conclusions are still problematic because the composition of the non-blue light emitted by the different types of lamps used is different. For example, although the dry weight of soybean and sorghum plants grown under the same light intensity lamp and the net photosynthetic rate per unit leaf area are significantly higher than those grown under low pressure sodium lamps, these results cannot be completely attributed to blue light under low pressure sodium lamps. Lack, I am afraid it is also related to the yellow and green light under the low-pressure sodium lamp and the orange red light.