Effects of LED light spectra on active oxygen metabolism and expression of antioxidant isozymes in Houttuynia cordata Thunb. seedlings
Abstract
The effects of various LEDs on active oxygen metabolism and patterns of SOD, POD and CAT isozymes in Houttuynia cordata Thunb. seedlings were investigated. After three weeks of light treatment, the MDA content was higher under blue LED compared with the control (P﹤0.05), while it decreased under white, red and yellow LEDs (P﹤0.05). The content of H2O2 was gradually increased in red, yellow, green and blue LEDs. The production rate of superoxide anion increased under yellow and blue LEDs by contrast with the control (P﹤0.05), and it decreased under white LED (P﹤0.05). LEDs altered the banding patterns of POD enzymes where the more loci of POD isozymes were observed under green and blue LEDs. The increased intensities of Fe-SOD were showed in green and blue LEDs. As for Mn-SOD and CAT enzymes, enhanced intensities appeared in all LED groups compared with the control. Our results indicated that the antioxidant system of Houttuynia cordata seedlings were more sensitive to short light wavelength than the long ones.
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Introduction
Among environment factors, light is not only an essential energy source for plant but also an important signal influence plant development, biosynthesis and gene expression throughout the life cycle of a plant [1-2]. The light spectrum affects growth and photosynthesis of plants has been well demonstrated in many species [3-4].
The light-emitting diodes (LED) is a unique type of semiconductor diode which showed great advantages over existing indoor agricultural lighting wherein the adjustable light intensity and quality, high photoelectric conversion efficiency, longer life, and low thermal output, and so on [5]. LED has been applied in plant disease prevention [6], plant tissue culture [7-8], space agriculture [9] and alga incubation [10-11]. Some studies demonstrated that LED with certain spectra may improve antioxidant activity of pea seedlings [12]; influence antioxidant properties as well as growth and photosynthesis of leaf lettuce [13-14].
Houttuynia cordata Thunb. is one of authorized medical and edible plants by China's Ministry of Health. It is rich in nutritious for human being including certain secondary metabolites as rutin, quercitrin and quercetin which showed antioxidant effects. Li concluded light intensity affected yield and quality of Houttuynia cordata Thunb.[15],while there is little knowledge about oxidative metabolism in Houttuynia cordata Thunb. under different LED light spectra. In the present study, we investigated different LED light spectra on the contents of malondialdehyde (MDA), hydrogen peroxide (H2O2) and reactive oxygen species (ROS) of Houttuynia cordata Thunb. We also analyzed the alteration of antioxidant isozyme patterns.
Conclusion
The experiment suggested that the short wavelength light lead to more seriously oxidative damage than longer wavelengths. Upon varied LEDs treatment, short wavelength light promoted the accumulation of ROS which resulted in the improved antioxidase activities and more loci expression. By reason of the different expression of Fe-SOD and Mn-SOD, we deemed that light spectra have unlike mechanism on chloroplasts and mitochondria which need to further investigation.
