Abstract
Regulation of plant growth and development by light wavelength has been extensively studied. Less attention has been paid to effect of light wavelength on formation of plant metabolites. The objective of this study was to investigate whether formation of volatiles in preharvest and postharvest tea (Camellia sinensis) leaves can be regulated by light wavelength. In the present study, in contrast to the natural light or dark treatment, blue light (470 nm) and red light (660 nm) significantly increased most endogenous volatiles including volatile fatty acid derivatives (VFADs), volatile phenylpropanoids/benzenoids (VPBs), and volatile terpenes (VTs) in the preharvest tea leaves. Furthermore, blue and red lights significantly up-regulated the expression levels of 9/13-lipoxygenases involved in VFADs formation, phenylalanine ammonialyase involved in VPBs formation, and terpene synthases involved in VTs formation. Single light wavelength had less remarkable influences on formation of volatiles in the postharvest leaves compared with the preharvest leaves. These results suggest that blue and red lights can be promising technology for remodeling the aroma of preharvest tea leaves. Furthermore, our study provided evidence that light wavelength can activate the expression of key genes involved in formation of plant volatiles for the first time.
Highlights
In plants by light, it is reported that light reflected from red mulch can improve concentrations of aroma compounds in strawberries[4]; volatile profiles of postharvest petunia flowers, tomato, strawberry, and blue-berry can be manipulated with specific light treatments[5]; aroma content of fresh basil leaves can be affected by light reflected from colored mulches[6]
Light emitting diodes (LED) was applied to treat preharvest tea leaves from the 1st leaf stage to the 4th leaf stage (14 days), and the results showed that in contrast to dark treatment as a control, blue light and red light increased the contents of volatile fatty acid derivatives (VFADs) and volatile phenylpropanoids/benzenoids (VPBs), whereas near-infrared light had less effect on tea volatiles
3 days of blue light and red light treatments on the 4th leaf stage of preharvest tea leaves increased most endogenous volatiles including VFADs, VPBs, and volatile terpenes (VTs) compared with dark treatment (Figs 1–3)
Summary
In plants by light, it is reported that light reflected from red mulch can improve concentrations of aroma compounds in strawberries[4]; volatile profiles of postharvest petunia flowers, tomato, strawberry, and blue-berry can be manipulated with specific light treatments[5]; aroma content of fresh basil leaves can be affected by light reflected from colored mulches[6]. These literatures show some evidences that light has potential to regulate the production of volatile molecules in planta. We investigated effect of light wavelength on formation of volatiles in postharvest tea leaves and evaluated if LED could be employed to tea manufacturing process to improve tea aroma quality
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