Effects of continuous LED lighting on reducing nitrate content and enhancing edible quality of lettuce during pre-harvest stage

Lettuce easily accumulates higher nitrate content during production, especially in hydroponic system, and higher ni trate content poses a threat to human health. Light condition (light quality, intensity and duration) significantly affects nitrate content in plants. Lighting -emitting diodes (LEDs) have showed the great potential for plant growth and development with the higher luminous efficiency and positive impact compared with other artificial light. The effects of combination of red (R)/ blue (B) or/and green (G), and white (W) LED lights on the plant growth, plant physiological 8th 45 International Symposium on Light in Horticulture changes, including chlorophyll fluorescence, nitrate contents and phytochemical concentration before harvest were investigated. The results showed that Pre-harvest continuous light exposure can effectively reduce nitrate accumulation and increase phytochemical concentrations in lettuce plants, and the reduction in nitrate content is dependent on the spectral composition and light intensity of the applied light sources and continuous light duration. Lettuce plants grown under the continuous combined red, green and blue LED light (RGB) with a PPFD at 200 μmol·m-2·s -(RGB-200) and RB-200 treatments exhibited a remarkable decrease of nitrate contents at 24 h compared to other LED light treatments. Moreover, continuous LED light at 24 h significantly enhanced the DPPH free-radical scavenging activity and increase phenolic compound concentrations. In this study, we suggest that a period of continuous LED light (RGB-200 or RB -200) exposure is needed in order to decrease nitrate concentrations and enhance lettuce quality. The period of 24 h continuous LED light exposure appears to be the best, and this period should not exceed 48 h

Isolation and drought-tolerant function analysis of ZmPti1-1, a homologue to Pti1, from maize (Zea mays L.)

Pto-interacting 1(Pti1) has been well established to play important roles in plant disease and salt response, but its potential roles in the response to drought stress is unknown. In this study, the Pti1- like gene named as ZmPti1-1 was cloned from maize, sequence analysis showed that ZmPti1-1 encodes a polypeptide of 363 amino acids with predicted molecular mass of 39.0 kDa and an isoelectric point of 8.14. ZmPt1-1 is dramatically induced by abscisic acid (ABA) and mannitol (data not shown). In order to analyze the further drought tolerant functions, ZmPti1-1 was over-expressed in Arabidopsis. Under drought stress, compared with wild type, survival rate of the three transgenic lines, which was 70, 76 and 87%, respectively, was significantly higher than that of wild type which was 29%; there were lower water loss, lower cell membrane damage, higher relative water content, higher total soluble sugars, higher proline content and higher yield for transgenic plants. Based on the present knowledge, this is the first report that over-expression of Pti1-like gene improved drought tolerance in plants.Key words: ZmPti1-1, transgenic Arabidopsis, drought tolerance

Effect of green light on nitrate reduction and edible quality of hydroponically grown lettuce (Lactuca sativa L.) under short-term continuous light from red and blue light-emitting diodes

Most leafy vegetables can accumulate large amounts of nitrate, which are often associated with harmful effects on human health. Nitrate assimilation in plants is determined by various growth conditions, especially light conditions including light intensity, light duration and light spectral composition. Red and blue light are the most important since both drive photosynthesis. Increasingly, recent evidence demonstrates a role for green light in the regulation of plant growth and development by regulating the expression of some specific genes. However, the effect of green light on nitrate assimilation has been underestimated. In this study, lettuce (Lactuca sativa L. cv. Butterhead) was treated with continuous light (CL) for 48h by combined red and blue light-emitting diodes (LEDs) supplemented with or without green LED in an environment-controlled growth chamber. The results showed that nitrate reductase (NR) and nitrite reductase (NiR) related-gene expression and nitrate assimilation enzyme activities were affected by light spectral composition and light duration of CL. Adding green light to red and blue light promoted NR and NiR expressions at 24h, subsequently, it reduced expression of these genes during CL. Compared with red and blue LEDs, green light supplementation significantly increased NR, NiR, glutamate synthase (GOGAT) and glutamine synthetase (GS) activities. Green-light supplementation under red and blue light was more efficient in promoting nutritional values by maintaining high net photosynthetic rates (Pn) and maximal photochemical efficiency (Fv/Fm)

A comparison of the local spiral structure from Gaia DR2 and VLBI maser parallaxes

Context. The Gaia mission has released the second data set (Gaia DR2), which contains parallaxes and proper motions for a large number of massive, young stars. Aims. We investigate the spiral structure in the solar neighborhood revealed by Gaia DR2 and compare it with that depicted by VLBI maser parallaxes. Methods. We examined three samples with different constraints on parallax uncertainty and distance errors and stellar spectral types: (1) all OB stars with parallax errors of less than 10%; (2) only O-type stars with 0.1 mas errors imposed and with parallax distance errors of less than 0.2 kpc; and (3) only O-type stars with 0.05 mas errors imposed and with parallax distance errors of less than 0.3 kpc. Results. In spite of the significant distance uncertainties for stars in DR2 beyond 1.4 kpc, the spiral structure in the solar neighborhood demonstrated by Gaia agrees well with that illustrated by VLBI maser results. The O-type stars available from DR2 extend the spiral arm models determined from VLBI maser parallaxes into the fourth Galactic quadrant, and suggest the existence of a new spur between the Local and Sagittarius arms.Comment: 4 pages, 3 figures, 1 table, accepted for publication in A&

The cumulative effects of known susceptibility variants to predict primary biliary cirrhosis risk.

Multiple genetic variants influence the risk for development of primary biliary cirrhosis (PBC). To explore the cumulative effects of known susceptibility loci on risk, we utilized a weighted genetic risk score (wGRS) to evaluate whether genetic information can predict susceptibility. The wGRS was created using 26 known susceptibility loci and investigated in 1840 UK PBC and 5164 controls. Our data indicate that the wGRS was significantly different between PBC and controls (P=1.61E-142). Moreover, we assessed predictive performance of wGRS on disease status by calculating the area under the receiver operator characteristic curve. The area under curve for the purely genetic model was 0.72 and for gender plus genetic model was 0.82, with confidence limits substantially above random predictions. The risk of PBC using logistic regression was estimated after dividing individuals into quartiles. Individuals in the highest disclosed risk group demonstrated a substantially increased risk for PBC compared with the lowest risk group (odds ratio: 9.3, P=1.91E-084). Finally, we validated our findings in an analysis of an Italian PBC cohort. Our data suggested that the wGRS, utilizing genetic variants, was significantly associated with increased risk for PBC with consistent discriminant ability. Our study is a first step toward risk prediction for PBC

Selenium distribution and nitrate metabolism in hydroponic lettuce (Lactuca sativa L.): Effects of selenium forms and light spectra

A deficiency in selenium (Se) in the human diet is a worldwide problem. The intake of Se-rich vegetables can be a safe way to combat Se deficiency for humans. However, most leafy vegetables can accumulate a high content of nitrates, which poses a potential threat to human health. Light is an important environmental factor that regulates the uptake and distribution of mineral elements and nitrogen metabolism in plants. However, the effects of Se forms and light conditions, especially light spectra, on the uptake and translocation of Se and on nitrate reduction are poorly understood. In this study, lettuce (Lactuca sativa L.) was treated with exogenous Se applied as selenate (10 mmol L−1) and selenite (0.5 mmol L−1) and grown under five different light spectra: fluorescent light (FL), monochromatic red LED light (R), monochromatic blue LED light (B), and mixed red and blue LED light with a red to blue light ratio at 4 (R/B=4), 8 (R/B=8), and 12 (R/B=12), respectively. The effects of light spectra and Se forms on plant growth, photosynthetic performance, Se accumulation and nitrate reduction were investigated. The results showed that the light spectra and Se forms had significant interactions for plant growth, foliar Se accumulation and nitrate reduction. The Se concentration and nitrate content in the leaves were negatively correlated with the percentage of red light from the light sources. Compared to Se applied as selenite, exogenous Se applied as selenate was more effective in reducing nitrate via promoting nitrate reductase and glutamate synthase activities. The lowest nitrate content and highest plant biomass were observed under R/B=8 for both the selenate and selenite treatments. The significant effect of the light spectra on the root concentration factor and translocation factor of Se resulted in marked variations in the Se concentrations in the roots and leaves. Compared with FL, red and blue LED light led to significant decreases in the foliar Se concentration. The results from this study suggest that the light spectra can contribute to Se distribution and accumulation to produce vegetables with better food quality

Insights into the Anaerobic Biodegradation Pathway of n-Alkanes in Oil Reservoirs by Detection of Signature Metabolites

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Extracting the phase information from atomic memory by intensity correlation measurement

We demonstrate experimentally controlled storage and retrieval of the optical phase information in a higher-order interference scheme based on Raman process in 87Rb atomic vapor cells. An interference pattern is observed in intensity correlation measurement between the write Stokes field and the delayed read Stokes field as the phase of the Raman write field is scanned. This result implies that the phase information of the Raman write field can be written into the atomic spin wave via Raman process in a high gain regime and subsequently read out via a spin-wave enhanced Raman process, thus achieving optical storage of phase information. This technique should find applications in optical phase image storage, holography and information processing