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Chengbo Zhou,Qi Wang,Wenke Liu,Baoshi Li,Mingjie Shao,Yubin Zhang 한국원예학회 2022 Horticulture, Environment, and Biotechnology Vol.63 No.2
Light is a crucial signal for plant growth, development, and secondary metabolism. Exploring the effects of light on autotoxin secretion in lettuce can be helpful for improving the utilization efficiency of the nutrient solution in plant factories. The effects of white light (WL) and the combination of red (R) and blue (B) light (RB, 4R:1B) at different intensities (150, 200, and 250 μmol m −2 s −1) on the growth and root exudates of hydroponic lettuce (Lactuca sativa L.) were studied in a closed plant factory. The lettuce biomass and photosynthetic rate increased with the increasing light intensity, and the photosynthetic rate was significantly lower under WL than under RB at both 200 and 250 μmol m −2 s −1 . Lettuce under WL had the longest root length and highest root surface area at 200 μmol m −2 s −1 , while the root length, root surface area, and root volume under RB were the highest at 250 μmol m −2 s −1 . Total organic carbon (TOC) content of root exudates in the nutrient solution based on shoot or root dry weight decreased with the increasing light intensity. With the increase in light intensity, the secretion of four autotoxins (benzoic acid, ferulic acid, gallic acid, and tannic acid) based on shoot dry weight and root dry weight decreased under WL. Compared with RB, WL significantly reduced the secretion of autotoxins at 250 μmol m −2 s −1 . In conclusion, 250 μmol m −2 s −1 white light should be used for high lettuce yield, and it could also decrease the autotoxins in the nutrient solution and the occurrence of autotoxicity.
Precipitation Behavior in Al-Zn-Mg-Cu Alloy After Direct Quenching
Shengdan Liu,Chengbo Li,Yunlai Deng,Xinming Zhang,Qiming Zhong 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.2
The precipitation behavior in an Al-6.8Zn-1.9Mg-1.0Cu-0.12Zr alloy after direct quenching from solutionheat treatment temperature of 470 °C to 205-355 °C was investigated by means of hardness tests, electricalconductivity tests, and transmission electron microscopy. At temperatures below 265 °C, the hardnessincreased gradually to a peak value and then decreased rapidly with time. At 265 °C, the hardness wasalmost unchanged within the initial 2000 s and then decreased gradually. At higher temperatures, the hardnessdecreased slowly with time. The electrical conductivity started to increase after a certain period oftime and then tended to maintain a constant value at all temperatures. Microstructure examination indicatedheterogeneous precipitation of the η phase at grain boundaries and inside grains during holding at205 °C and 325 °C. Based on the electrical conductivity data, the precipitation kinetics could be describedquite well by the Johnson-Mehl-Avrami-Komolgorov relationship with a n value varying between 0.78 and1.33. The activation energy was estimated to be about 44.9 kJ/mol, which is close to that expected for a dislocationdiffusion mechanism. Time-temperature-transformation diagrams were constructed and the nosetemperature ranged from 295 °C to 325 °C.
Mingjie Shao,Wenke Liu,Lingyan Zha,Chengbo Zhou,Yubin Zhang,Baoshi Li 한국원예학회 2020 Horticulture, Environment, and Biotechnology Vol.61 No.6
This study investigated the eff ects of constant light and alternating relatively high-intensity (500 μmol m −2 s −1 ) and lowintensity(150 μmol m −2 s −1 ) red–blue LEDs (4R:1B) on the biomass production and quality of hydroponic purple-leaf lettuce( Lactuca sativa L. cv. ‘Zishan’) in an environmentally controlled plant factory. Four treatments were set up to separate1 h of high light into four diff erent alternating frequencies in a 24-h light−dark cycle (16/8 h): one time (A1), three times(A3), six times (A6), and twelve times (A12). In addition, one constant light treatment with the same daily light integral(DLI, 9.8 mol m −2 per day) as other treatments was set as the control (CK, 170 μmol m −2 s −1 ). The results indicated thatA6 signifi cantly reduced shoot fresh weight and increased the root–shoot ratio of lettuce compared with CK, but there wasno signifi cant diff erence among other treatments. Alternating light treatments did not promote the accumulation of solublesugar, soluble protein, and phenolic substances compared with CK. Meanwhile, A12 signifi cantly promoted the accumulationof total ascorbate (TA) in lettuce leaves compared with other treatments but decreased ascorbate/TA ratio. Above all, underthe same DLI condition, alternating high and low light did not have obvious positive eff ects on biomass production and theaccumulation of nutrient substance in lettuce under constant light was better than that under alternating light. Therefore,compared with the fl uctuating radiation with the same DLI, constant radiation is a better choice for lettuce production.