Effects of Different Ratios of Green-Blue Light on Basil Growth and Its Energy Use Efficiency
[Objective]This study aimed to investigate the effects of different ratios of green-blue light(G/B)with constant red light(R,660 nm)on the growth,stomatal characteristics,photosynthetic capacity,and energy utilization efficiency of basil plants(Ocimum basilicum Linn.).The ultimate goal of this study was to provide the technical support for efficient and energy-saving production of basil plants in plant factory.[Method]Basil seedlings were subjected to seven different light quality treatments of RB(R:G:B=8:0:8,set as control),RG1B7(R:G:B=8:1:7),RG1B3(R:G:B=8:2:6),RG1B1(R:G:B=8:4:4),RG3B1(R:G:B=8:6:2),RG7B1(R:G:B=8:7:1),and RG(R:G:B=8:8:0)for a duration of 19 days after transplanting.The total light intensity was 160 μmol·m-2·s-1,with red light accounting for 50%of the total light intensity.The photo/dark period was 16/8 hours per day.The air temperature during the light/dark period was set at 25℃/23℃,and the relative humidity was set at 65%.Additionally,the CO2 concentration during the light period was 1 000 μmol·mol-1.The photosynthesis parameters of basil plants were determined after 13 days of experimental treatment,while the growth parameters,stomatal characteristics,and energy use efficiency of basil plants were determined after 19 days of experimental treatment.[Result]Except for treatment RG1B3,the addition of green light significantly enhanced height,leaf area,and dry and fresh weight of basil plants.The shoot dry and fresh weights of basil plants under different G/B treatments showed an increase of 19%-51%and 26%-64%,respectively,compared with those under the control.However,no significant differences in leaf area and dry/fresh weights were observed among the G/B treatments,except those under treatment RG.The treatment with low G/B(RG1B7)only caused a reduction in the stomatal density on the abaxial surface of basil lower leaves.As G/B increased,the stomatal density decreased on the adaxial surface of the lower leaves and both surfaces of the upper leaves.In general,the leaf nitrogen content decreased with an increase in the G/B.This decrease in leaf nitrogen content and stomatal density resulted in a decline in CO2 assimilation capacity and light utilization capacity of basil plants.The reduction in these capacities generally increased with the increasing G/B.Due to the lower light-emitting efficiency of green LEDs compared with blue light,the total power consumption increased with an increase in the G/B.Only the treatment RG1B7 significantly improved electric use efficiency by 25%than that under the control.With the exception of RG1B3,all other G/B treatments improved light utilization efficiency by 30%-57%than that under the control,and no significant differences were found among different G/B treatments,except for RG.RG3B1 and RG improved water use efficiency of both upper and lower basil leaves,with RG3B1 showing a 58%and 74%increase,and RG showing a 67%and 90%increase,respectively compared with that under the control.[Conclusion]By comprehensively analyzing,basil plants growth and energy utilization efficiency,the RG1B7 could be considered as a more suitable light quality combination for basil plants production in plant factories.The findings of this study could serve as a technical support for understanding the impact of different G/B ratios on basil growth,photosynthetic characteristics,and energy utilization efficiency.This research provided the valuable insights for developing optimized light formulations that enable efficient and energy-saving production of basil plants in plant factory environments.
basilthe ratio of green-blue lightlight qualitygrowthphotosyntheticenergy use efficiency
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