Responses of dark respiration in the light to desiccation and temperature in the intertidal macroalga, Ulva lactuca (Chorophyta) during emersion

Dark respiration (nonphotorespiratory mitochondrial CO2 release) in the light (R-L) of the intertidal macroalga Ulva lactuca (Chorophyta) during emersion was investigated with respect to its response to variations in temperature and desiccation. R-L was estimated by CO2 gas-exchange analysis using the Kok effect method, whereas dark respiration in darkness (R-D) was determined from CO2 release at zero light. Rates of R, were significantly and consistently lower than those of R-D in emersed U. lactuca across all the temperature and desiccation levels measured. This demonstrated that dark respiration was partially depressed in the light, with the percentage inhibition ranging from 32 to 62%. Desiccation exerted a negative effect on R-L and R-D at a high temperature, 33 degrees C, whereas it had much less effect on respiration at low and moderate temperatures, 23 and 28 degrees C. In general, R-L and R-D increased with increasing temperature in U. lactuca during all stages of emersion but responded less positively to temperature change with increasing desiccation. Additionally, the Q(10) value (i.e. the proportional increase of respiration for each 10 degrees C rise in temperature) for R-L calculated over the temperature range of 23 to 33 degrees C was significantly higher than that for R-D in U. lactuca during the initial stages of emersion. Respiratory carbon loss as a percentage of gross photosynthetic carbon gain increased with increasing temperature and/or desiccation but was significantly reduced when estimated using R-L rather than R-D. It is suggested that measurements of R-L and how it changes in a variable environment are as important as estimates of R-D and photosynthesis in determining simultaneous balance between photosynthetic carbon uptake and respiratory carbon loss and in modeling the net daily carbon gain for an intertidal macroalga.Dark respiration (nonphotorespiratory mitochondrial CO2 release) in the light (R-L) of the intertidal macroalga Ulva lactuca (Chorophyta) during emersion was investigated with respect to its response to variations in temperature and desiccation. R-L was estimated by CO2 gas-exchange analysis using the Kok effect method, whereas dark respiration in darkness (R-D) was determined from CO2 release at zero light. Rates of R, were significantly and consistently lower than those of R-D in emersed U. lactuca across all the temperature and desiccation levels measured. This demonstrated that dark respiration was partially depressed in the light, with the percentage inhibition ranging from 32 to 62%. Desiccation exerted a negative effect on R-L and R-D at a high temperature, 33 degrees C, whereas it had much less effect on respiration at low and moderate temperatures, 23 and 28 degrees C. In general, R-L and R-D increased with increasing temperature in U. lactuca during all stages of emersion but responded less positively to temperature change with increasing desiccation. Additionally, the Q(10) value (i.e. the proportional increase of respiration for each 10 degrees C rise in temperature) for R-L calculated over the temperature range of 23 to 33 degrees C was significantly higher than that for R-D in U. lactuca during the initial stages of emersion. Respiratory carbon loss as a percentage of gross photosynthetic carbon gain increased with increasing temperature and/or desiccation but was significantly reduced when estimated using R-L rather than R-D. It is suggested that measurements of R-L and how it changes in a variable environment are as important as estimates of R-D and photosynthesis in determining simultaneous balance between photosynthetic carbon uptake and respiratory carbon loss and in modeling the net daily carbon gain for an intertidal macroalga

Ginsenoside Rb1 Prevents H2O2-Induced HUVEC Senescence by Stimulating Sirtuin-1 Pathway

We have previously reported that Ginsenoside Rb1 may effectively prevent HUVECs from senescence, however, the detailed mechanism has not demonstrated up to now. Recent studies have shown that sirtuin-1 (Sirt1) plays an important role in the development of endothelial senescence. The purpose of this study was to explore whether Sirt1 is involved in the action of Ginsenoside Rb1 regarding protection against H2O2-induced HUVEC Senescence.Senescence induced by hydrogen peroxide (H2O2) in human umbilical vein endothelial cells (HUVECs) was examined by analyzing plasminogen activator inhibitor-1 (PAI-1) expression, cell morphology, and senescence-associated beta-galactosidase (SA-β-gal) activity. The results revealed that 42% of control-treated HUVECs were SA-β-gal positive after treatment by 60 µmol/L H2O2, however, this particular effect of H2O2 was decreased more than 2-fold (19%) in the HUVECs when pretreated with Rb1 (20 µmol/L) for 30 min. Additionally, Rb1 decreased eNOS acetylation, as well as promoted more NO production that was accompanied by an increase in Sirt1 expression. Furthermore, upon knocking down Sirt1, the effect of Rb1 on HUVEC senescence was blunted.The present study indicated that Ginsenoside Rb1 acts through stimulating Sirt1 in order to protect against endothelial senescence and dysfunction. As such, Sirt1 appears to be of particular importance in maintaining endothelial functions and delaying vascular aging

Comparative physiological behaviors of Ulva lactuca and Gracilariopsis lemaneiformis in responses to elevated atmospheric CO2 and temperature

Physiological metabolisms of seaweeds usually suffered climate changes in the field. Gracilariopsis lemaneiformis and Ulva lactuca, collected from Nan'ao Island, Shantou, China, were cultured under ambient and elevated CO2 supply (390 and 800 mu l L-1), with low and high temperatures (15 A degrees C and 25 A degrees C) for 2 weeks, aiming to compare the difference of the main physiological metabolism between two seaweed species in response to the elevated CO2 and high temperature. At 15 A degrees C, the pH reduction in the culture medium caused by elevated CO2 was larger in G. lemaneiformis than in U. lactuca. At 25 A degrees C, elevated CO2 significantly increased photosynthetic rates (P-n or P-g) and maintained constant respiratory rates (R-d) in G. lemaneiformis. However, for 25 A degrees C-grown U. lactuca, the increment of CO2 did not enhance the P-n (P-g) rates but rapidly decreased the R-d rates itself. With the higher R-d/P-g ratios in G. lemaneiformis than U. lactuca, the warming thereby promoted more allocation of photosynthetic products to respiratory consumption in G. lemaneiformis. Both P-g and R-d rates exhibited lower temperature acclimation in two seaweeds. In addition, elevated CO2 markedly increased the relative growth rate (RGR) and phycobiliprotein (PB) contents at 25 A degrees C, but exhibited no enhancement of chlorophyll a (Chl a), carotenoids (Car), soluble carbohydrate (SC), and soluble protein (SP) contents in G. lemaneiformis, with the reduction of SC when temperature increased only. We suggested that climate changes were probably a more benefit to U. lactuca than to G. lemaneiformis, inherently justifying the metabolism during G. lemaneiformis maricultivation

Effects of selenite on growth, photosynthesis and antioxidant system in seaweeds, Ulva fasciata (Chlorophyta) and Gracilaria lemaneiformis (Rhodophyta)

Selenium (Se) is an essential trace element for plants, animals and humans. Se enrichment has been deemed as a new approach to enhance the nutrient and economic value of seaweed to make it commercially competitive. To explore the effects of Se on seaweed photosynthesis, Ulva fasciata (Chlorophyta) and Gracilaria lemaneiformis (Rhodophyta) were cultured over 1 week in selenite (Na2SeO3) concentrations of 0, 200, 500, 800 mg L-1 . Our results showed that, U. fasciata and G. lemaneiformis effectively accumulated Se and transformed inorganic Se to organic Se at the rate of about 80% during cultivation. Se exerted positive effect on growth and photosynthesis in the three Se concentrations (200, 500, 800 mg L-1 selenite) with the optimum concentration 200 mg L-1 in Ulva and 500 mg L-1 in Gracilaria, and Se promoted growth of seaweeds Gracilaria and Ulva, accumulating more soluble protein (SP) and carbohydrate (SC). Also, photosynthesis was improved by promotion of photosynthetic pigments (Chl a, Car, PE, PC), stimulation of photosystem II (PSII) (F-v/F-m a, rETRm), and enhancement of photosynthetic oxygen evolution (Pn, AE). In addition, Se stimulated activities of SOD, POD, CAT and GPX with all Se concentrations in Ulva and Gracilaria, and substantially decreased MDA levels in 200 mg L-1 selenite, indicating that Se could increase antioxidative activity and enhance antioxidant system. We proposed that enhanced defensive system of antioxidants by Se could improve and protect photosynthesis to some extent

Time-evolving seismic tomography: The method and its application to the 1989 Loma Prieta and 2014 South Napa earthquake area, California

We propose a time‐evolving approach to conduct traveltime seismic tomography in the 1989 Mw 6.9 Loma Prieta earthquake and 2014 Mw 6.0 South Napa earthquake area, California. The recording period of the chosen seismic data between 1 January 1967 and the day before the 2014 South Napa earthquake is divided into two time windows, separated by the 1989 Loma Prieta earthquake. In each time window the subsurface velocity structure is iteratively updated. Starting from the final model of the first time window, the velocity model has been successively improved throughout iterations in the second time window, indicating that the traveltime data of later time windows have provided extra information to refine the subsurface images. Strong heterogeneities are observed in the final P wave velocity model. Both of the two large earthquakes occurred at transition zones in between high VP and low VP anomalies. In all, this study shows the effectiveness of the time‐evolving seismic tomography method.Published versio