文献 | 量子荧光|微型光纤光谱仪-ag贵宾会

in this study, we determined the effects of raising seedlings with different light spectra such as with blue, red, and blue red light-emitting diode (led) lights on seedling quality and yield of red leaf lettuce plants. the light treatments we used were applied for a period of 1 week and consisted of 100 mmol_m–2_s–1 of blue light, simultaneous irradiation with 50 mmol_m–2_s–1 of blue light and 50 mmol_m–2_s–1 of red light, and 100 mmol_m–2_s–1 of red light. at the end of the light treatment, that is 17 days after sowing (das), the leaf area and shoot fresh weight (fw) of the lettuce seedlings treated with red light increased by 33% and 25%, respectively, and the dry weight of the shoots and roots of the lettuce seedlings treated with blue-containing led lights increased by greater than 29% and greater than 83% compared with seedlings grown under a white fluorescent lamp (fl). the shoot/root ratio and specific leaf area of plants irradiated with blue-containing led lights decreased. at 45 das, higher leaf areas and fws were obtained in lettuce plants treated with blue-containing led lights. the total chlorophyll (chl) contents in lettuce plants treated with blue-containing and red lights were less than that of lettuce plants treated with fl, but the chl a/b ratio and carotenoid content increased under blue-containing led lights. polyphenol contents and the total antioxidant status (tas) were greater in lettuce seedlings treated with blue-containing led lights than in those treated with fl at 17 das. the higher polyphenol contents and tas in lettuce seedlings at 17 das decreased in lettuce plants at 45 das. in conclusion, our results indicate that raising seedlings treated with blue light promoted the growth of lettuce plants after transplanting. this is likely because of high shoot and root biomasses, a high content of photosynthetic pigments, and high antioxidant activities in the lettuce seedlings before transplanting. the compact morphology of lettuce seedlings treated with blue led light would be also useful for transplanting.

the analytical development and underlying hypothesis of a three-band algorithm for estimating chlorophyll-a concentration ([chla]) in turbid productive waters are presented. the sensitivity of the algorithm to the spectral location of the bands used is analyzed. a large set of experimental observations ([chla] varied between 4 and 217 mg m 3 and turbidity between 2 and 78 nephelometric turbidity units) was used to calibrate and validate the algorithm. it was found that the variability of the chlorophyll-a fluorescence quantum yield and of the chlorophyll-a specific absorption coefficient can reduce considerably the accuracy of remote predictions of [chla]. instead of parameterizing these interferences, their effects were minimized by tuning the spectral regions used in the algorithm. this allowed us to predict [chla] with a relative root-mean-square error of less than 30%.

 the effects of drought, enhanced uv-b radiation and their combination on plant growth and physiological traits were investigated in a greenhouse experiment in two populations of populus cathayana rehder originating from high and low altitude in south-west china. in both populations, drought significantly decreased biomass accumulation and gas exchange parameters, including net co2 assimilation rate (a), stomatal conductance (gs), transpiration rate (e) and photosynthetic nitrogen use efficiency (pnue). however, instantaneous water use efficiency (wuei), transpiration efficiency (wuet), carbon isotope composition (δ13c) and nitrogen (n) content, as well as the accumulation of soluble protein, uv-absorbing compounds and abscisic acid (aba) significantly increased in response to drought. on the other hand, cuttings from both populations, when kept under enhanced uv-b radiation, showed very similar changes, as under drought, in all above-mentioned parameters.  compared with the low altitude population, the high altitude population was more tolerant to drought and enhanced uv-b, as indicated by the higher level of biomass accumulation, gas exchange, water-use efficiency, aba concentration and uv-absorbing compounds.  after one growing season of exposure to different uv-b levels and watering regimes, the decrease in biomass accumulation and gas exchange, induced by drought, was more pronounced under the combination of uv-b and drought. significant interactions between drought and uv-b were observed in wuei, wuet, δ13c, soluble protein, uv-absorbing compounds, aba and in the leaf and stem n, as well as in the leaf and stem c:n ratio.  our results showed that uv-b acts as an important signal allowing p. cathayana seedlings to respond to drought and that the combination of drought and uv-b may cause synergistically detrimental effects on plant growth.

to adequately image through a water column and to delineate variation in coral reef ecosystem benthic types, sensors having high spatial, e.g., a cirrus digital camera system (dcs), and spectral, e.g., the airborne visible infrared imaging spectrometer (aviris), resolution and high signal to noise are needed. further, there is a need to better understand the optical properties of coral reefs, seagrass, other benthic types, and water column constituents from field-collected data so current and future remote sensing can be optimized for coastal zone ecosystem research and management. in august 2004, we flew the aviris and dcs on a nasa er-2 over the florida keys and puerto rico. in march 2005, we flew aviris/dcs on the twin otter over kaneohe bay, oahu. also, in december 2005, we flew aviris/dcs on the twin otter over puerto rico and the us virgin islands for assessment of the 2005 caribbean coral reef bleaching event. for each of these deployments, we collected coincident spectral data from dominant bottom types and coral under various health conditions using a hand-held spectroradiometer. these spectral data will be used to classify the benthic types within the aviris imagery. an overview of the airborne missions and coincident field data collection will be presented along with preliminary image and field-collected spectral data products.