| Space cosmic radiation is one of the most serious problems encountered by astronaut onthe long-duration manned space flight mission and settlement and development ofextraterrestrial planets like Moon and Mars, that can be defensed effectively throughconsumption of antioxidants. Therefore, cultivation of fresh fruits and vegetables rich inantioxidants in the Controlled Ecological Life Support System (CELSS) for astronaut dietcould improve their anti-space radiation capacity, thereby ensuring the health and safety ofastronauts.In this research, a closed and controlled plant chamber and Gynura Bicolor DC rich inantioxidant were employed as the experimental platform and plant material. Light-emittingdiodes (LED) were applicated as light source, and different combination and proportions ofLED were constructed and builded as light quality module area. Under the closed controlledenvironment, we investigated the joint influences and mechanism of some controllableenvironmental factors such as LED light qualities, CO2levels and UV-B radiation on growthand antioxidant of Gynura Bicolor DC for the first time by using plant physiological andbiochemical relevant analysis technology to define the opitimized environmental conditionsfor plant growth and the accumulation of antioxidant, and determine their tolerance toextreme environments like super-elevated CO2and high intensity UV-B radiation. Thefinding from such a study could provide theoretical basis for the production and application ofGynura Bicolor DC in CELSS. The main results were as follows:1. The interactional effect of light quality and CO2level on plants biomass accumulationwas significant. Plants biomass was improved by the combination of red and bluespectrum as compared with full spectrum (WL), and that was promoted by blue lightswith a range of15～20%. Under the same light quality, there was no evident difference inplants biomass between control (450μmol·mol-1) and elevated CO2(1200～2000μmol·mol-1), but super-elevated CO2(8000μmol·mol-1) reduced plant biomass. Whengreen lights were added to red-blue light system, plant biomass in control and elevatedCO2was completely changed. Under control CO2, plants biomass in red-blue-green lightsystem was lower than that in red-blue light system. However, increased CO2improvedplants biomass in red-blue-green light system, leading to a comparative level of plantbiomass than that in red-blue light system. 2. Both blue lights and CO2enrichment were effective stimulus for phenols accumulation.Under the same CO2level, the combination of red and blue spectrum could accumulatemore phenols as compared with full spectrum (WL). Under control and elevated CO2,phenols contents were promoted by blue lights with a range of20～30%, whereas thosewere not further improved even reduced when increasing blue lights up to40%. Underthe same light quality, phenols accumulation was promoted at elevated CO2level of1200～1500μmol·mol-1, while such promotion was appeared to negate when increasingCO2up to2000μmol·mol-1. However, the further promotion of phenols contents wasobserved at super-elevated CO2. Under red-blue light system, elevated CO2with80%red+20%blue LED lights was the better condition for acquisition of maximum averagephenols yield.3. Green lights were not beneficial to phenols accumulation as compared with blue lights.Although phenols (flavonoids and anthocyanins) average yield (g·m-2) in elevated CO2was higher than that in control CO2, CO2increasing did not promote phenols contents(mg·g-1DW) in red-blue-green light system, the contents of some constitutes(anthocyanins and phenolics) were decreased, which was opposite to the situation inred-blue light system. In addition, under elevated CO2level, the addition of green light tobackground of red-blue lighting led to an apparently decereased total phenolicsconcentration and average yield.4. CO2enrichment was not conducive to volatile terpenoids accumulation, but green lightswere effective accelerant for volatile terpenoids accumulation. Increased CO2caused asignificant decrease in volatile terpenoids contents (mg·100g-1DW) and average yield(g·m-2) as compared with control CO2at both red-blue and red-blue-green light treatments;The addition of green lights evidently improved volatile terpenoids contents and averageyield both in control and elevated CO2. Under red-blue light system, the suitable conditionfor acquisition of maximum average terpenoids yield was at control CO2with80%red+20%blue LED lights, and that was at control CO2with60%red+20%blue+20%green LED lights under red-blue-green light system. Meanwhile, the comparative averageterpenoids yield was recorded in these two conditions.5. Gynura bicolor DC might have higher tolerance to CO2stress, and the increment of bluelights could relieve accelerated aging of plant under super-elevated CO2to some extent.Super-elevated CO2increased the activity of antioxidant enzymes and total antioxidantactivity to a greater extent as compared with control and elevated CO2. Moreover, the elevation of blue lights proportion promoted chlorophyll contents, reduced the massiveaccumulation of starch in plant cells and increased the capability of nitrogen assimilation.6. The effects of UV-B radiation on the growth and anti-oxidantive system were significant.Gynura Bicolor DC showed an apparent UV-sensitive phenotype when exposure to UV-Bradiation (1.29W·m-2/2.322KJ·m-2·day-1and0.79W·m-2/1.422and2.844KJ·m-2·day-1).UV-B exposure was found to lead to an evident growth-inhibition. Photosynthetic rate,transpiration rate, water use efficiency, chlorophyll and endogenous antioxidants (ASC,GSH) levels were significantly decreased with irradiation time increasing, but the contentof flavonoids and phenolics were increased dramaticllly, anthocyanins concentration wasnot changed markedly. Cell membrane folds and separation of chloroplasts and cell wallwere occurred on the plant leaves treated with high intensity of UV-B radiation. After theremoval of UV-B radiation, morphology of new plant leaf was recovered to the statebefore radiation. So, Gynura Bicolor DC had a good ability to repair.Based on the above results, the conclusion was as follows:1) Both in terms of biomassand secondary metabolites accumulation,80%red+20%blue LED lights was the suitablelighting condition for planting Gynura Bicolor DC., acquisition of maximum average phenolsyield needed assistance with elevated CO2concentration (1200～1500μmol mol-1) in thislight quality, but acquisition of maximum average terpenoids yield did not.2) Theaccumulation of terpenoids could be stimulated effectively by green LED lights, and theaddition of green LED lights to red-blue combination light quality significantly changed thebiomass and phenols accumulation in plant under control and elevated CO2.3) The incrementof blue lights could relieve accelerated aging of plant under super-elevated CO2, therebyinproving plant’s tolerance to CO2stress.4) Although Gynura Bicolor DC rich in secondarymetabolites showed an apparent UV-sensitive phenotype, they had good resilience to UV-Bradiation through increasing the accumulation of flavnoids and phenolics and changingmorphology of plant leaves. |
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