Green Fraction Research Articles

Variability in the Environmental Factors Driving Evapotranspiration from a Grazed Rangeland during Severe Drought Conditions

AbstractNearly one-half of the earth’s terrestrial surface is susceptible to drought, which can have significant social, economic, and environmental impacts. Therefore, it is important to develop better descriptions and models of the processes linking the land surface and atmosphere during drought. Using data collected during the International H2O Project, the study presented here investigates the effects of variations in the environmental factors driving the latent heat flux (λE) during drought conditions at a rangeland site located in the panhandle of Oklahoma. Specifically, this study focuses on the relationships of λE with vapor pressure deficit, wind speed, net radiation, soil moisture content, and greenness fraction. While each of these environmental factors has an influence, soil moisture content is the key control on λE. The role of soil moisture in regulating λE is explained in terms of the surface resistance to water vapor transfer. The results show that λE transitioned between being water or energy limited during the course of the drought. The implications of this on the ability to understand and model drought conditions and transitions into or out of droughts are discussed.

Vertical distribution of chloroform-extractable green fraction in several Andosol and Cambisol profiles

The vertical distribution of the content of the chloroform-extractable green fraction (CEGF) in the soil profiles of four Japanese Andosols, one Japanese Cambisol and one Nepalese Cambisol was examined using a colorimetric method with an ultraviolet and visible spectrophotometer. In addition, the relationship between the CEGF content and the soil chemical properties was examined by statistical analysis. CEGF was detected in all the soil samples, and the content ranged from 0.02 to 1.16 g kg−1. The CEGF content in the surface A horizon of the Andosol tended to be higher than in the Cambisol. The vertical distribution of the CEGF content in three soil profiles (two Andosol profiles and one Nepalese Cambisol) revealed maximum values in the subsurface horizon. In the Japanese Cambisol, the content of the CEGF was highest in the surface horizon. In the remaining two Andosol profiles containing a buried humus horizon, the content of the CEGF was highest in the buried humus horizon and the distribution was considerably different from that of organic carbon. Statistical analysis showed that the content of the CEGF displayed a significant positive correlation (P < 0.001, n = 36) with the contents of dithionite-citrate-bicarbonate-extractable Al (Ald), and with oxalate-oxalic acid-extractable Fe and Al (Feo and Alo, respectively). Furthermore, the content of the CEGF showed a significant positive correlation with the content of Alo (r = 0.944, P < 0.01, n = 6) in the soil with the highest content of CEGF in the profile. It was, therefore, suggested that CEGF is actively produced in humus-rich soils like Andosols, and that Ald, Feo and, in particular, Alo were associated with the vertical distribution of CEGF in the soil profiles.

Method for Estimating the Content of the Chloroform-Extractable Green Fraction (CEGF) in HCl-DMSO Extract of Soils

Chloroform-extractable green fraction (CEGF) was detected in the supernatant obtained by alkali precipitation from the HCI-dimethylsulfoxide (DMSO) extract of Pg-rich soil. In the alkaline solution, the color of CEGF was green and CEGF showed strong Pg-like absorption bands. Ultraviolet and visible (UV-VIS) spectral analysis and gel chromatography on Sephadex G-50 were performed to compare several properties between CEGF and Pg. CEGF, which was purified by gel chromatography on Bio-Beads SX-1, displayed strong absorption bands at 609, 562, 445 and 280 inn in the alkaline solution. These absorption bands were almost similar to those of Pg. Furthermore, the UV-VIS spectrum of CEGF in the organic solvents showed a similar characteristic pattern of 4,9-dihydroxyperylene-3,10-quinone (DHPQ), which was considered to be a chromophore of Pg. Based on the results of gel chromatography on Sephadex G-50, CEGF mainly consisted of two fractions, corresponding to the G2 and G3 fractions of Pg. These results indicated that the method for extracting CEGF from Pg-rich soil in the present study was easy and selective and that CEGF was one of the components of, or a closely related substance to Pg. A colorimetric method for the estimation of the CEGF content in soils was developed. The calibration curve of CEGF was linear over a wide range of contents from 2.75 to 220 mg L−1. The CEGF content in twelve samples of various soils was examined. CEGF was detected in all the soil sampled (5 orders) including three samples (3 orders) where Pg was not detected, and the content ranged from 0.07 to 1.66 g kg−1 (dry soil). Therefore, the method for estimating the CEGF content in soils developed in the present study was found to be suitable for various soil orders and it was assumed that CEGF occurred in various soil orders.

Electron spin resonance characteristics of humic acids from a wide range of soil types

Electron spin resonance (ESR) spectroscopy was applied to humic acids in solid and solution states obtained from a wide range of soil types. The relationships between the relative free-radical concentration and the degree of humification expressed as A 600/ C and log( A 400/ A 600) and the aromatic C concentration estimated by cross-polarization magic-angle spinning 13C nuclear magnetic resonance spectroscopy were analyzed. The hyperfine structure observed in solution ESR spectra was also compared among the humic acids. The free-radical concentration varied up to 147-fold among 42 humic acids, with a sample from a buried Umbric Andosol (Ando soil) having the greatest concentration and that from an upland field soil (Dystric Cambisol) the least. The linewidth of the radical signals ranged between 0.32 and 0.55 mT and showed an inverse correlation with the free-radical concentration, suggesting a decrease in the heterogeneity of free-radicals with their increase. The free-radical concentration was correlated ( P < 0.005) positively with the A 600/ C and the aromatic C concentration, whereas it varied in inverse proportion to the log( A 400/ A 600) value. Regression analysis suggested that the electron-conjugated systems are more developed in the humic acids with greater aromatic C concentration, which help stabilize free-radicals. Hyperfine splitting observed in the ESR spectra of a range of Ando soil humic acids dissolved in 0.1 M KOH was similar, while the peak strength decreased with increasing degree of humification. Although continuous application of manure to upland field soils scarcely affected the free-radical concentration in their humic acids, their hyperfine structure was weakened. The solution ESR spectra of the green fraction, which contains a chromophore related to 4,9-dihydroxyperylene-3,10-quinone (DHPQ) structure, was composed of basic features with an additional hyperfine structure superimposed on them. Since the basic features were consistent with the hyperfine structure of humic acids from Ando soils and the H layer of a Podzol which do not contain the green fraction, it was considered that the additional hyperfine structure is associated with DHPQ and thus the influence of DHPQ on the ESR spectra of humic acids is minor.

ON THE POTENTIAL OF SATELLITE DERIVED VEGETATION PHENOLOGY FOR WATERSHED NUTRIENT MODELING: A NEURAL NETWORK APPROACH

ON THE POTENTIAL OF SATELLITE DERIVED VEGETATION PHENOLOGY FOR WATERSHED NUTRIENT MODELING: A NEURAL NETWORK APPROACHTo our knowledge, this study is the first to attempt to build a model that can rely on a time series of remotely sensed vegetation indices (VIs) for predicting the dynamics of water-phase total phosphorus (TP) concentration. We examined the possibility of using four literature based VIs; enhanced vegetation index (EVI), normalized difference vegetation index (NDVI), greenness fraction vegetation...Author(s)M.H. NourA. KhanD.W. SmithM.G. Gamal El-DinSourceProceedings of the Water Environment FederationSubjectSession 84: Surface Water Quality & Ecology: Water Quality Modeling and TMDL DevelopmentDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2005ISSN1938-6478SICI1938-6478(20050101)2005:8L.6989;1-DOI10.2175/193864705783858846Volume / Issue2005 / 8Content sourceWEFTECFirst / last page(s)6989 - 7017Copyright2005Word count204

Seasonal, topographic and burn frequency effects on biophysical/spectral reflectance relationships in tallgrass prairie

Application of remote sensing relies on understanding how the physical properties of surfaces (especially vegetated surfaces) control spectral reflectance. Empirical investigation of links between canopy properties/processes and spectral response have generally consisted of univariate modelling of one spectral response variable in terms of one canopy property, or less frequently, in terms of two or more canopy variables. While this approach has been fruitful, it cannot account for multivariate interactions of spectral and surface properties in determining canopy response across the spectrum. In this study, two closely related multivariate analysis techniques, canonical correlation and redundancy analysis, are used to investigate the relationship between a series of tallgrass prairie canopy biophysical properties and spectral reflectance measured in situ using a portable radiometer. To capture a variety of different conditions within the tallgrass canopy, data were collected at two times during the 2002 growing season (28 May and 18 August), from two different slope/aspect situations, located on one frequently burned and one infrequently burned watershed. Results suggest that canopy structure (canopy height, greenness fraction) is the most consistent influence on spectral reflectance during both data collection periods. Canopy optical properties also emerge as an important control in August. Neither soil moisture nor plant physiology/biochemistry systematically influenced spectral reflectance. The relative importance of the various canopy variables shows some dependence on burn frequency and topographic setting.

Technologically indicative properties of straw fractions of flax, linseed ( Linum usitatissimum L.) and fibre hemp ( Cannabis sativa L.)

In this study of the behaviour of the fractions of unretted and frost-retted fibre straws in damp air, a production scale method to separate fibre and shive from fibre plants was introduced and tested on bast fibre plants ( Linum usitatissimum L. and Cannabis sativa L.). The method consists of optional drying of stalks, unloading bales, milling the straws with a hammer mill, separating the fractions from air stream with a cyclone and finally separating fibres from shives with a screening drum. Fractions were characterized focusing on technologically indicative properties such as equilibrium moisture content, ash and microbiological quality. Unretted fractions of the bast fibre plant stem reached higher equilibrium moisture contents than the retted fractions, and hemp fibres absorbed more moisture from air than did the Linum fibres. In very humid air, all fractions began to lose weight due to moulding. The weight decrease during the first week was lower in frost-retted than in unretted fractions. The frost-retted fractions appeared to be more resistant to humidity in the short term. The total number of microbes and especially the numbers of yeasts and moulds can be used as a criterion of hygienic level. For green fractions, the mould level was similar in fibres and in shives, but frost-retted shives contained more moulds than the unretted shives. The mould content of a fraction had no direct correlation with the moulding tendency of the fraction. The ash contents of fibres were somewhat higher than those of shives, due to a probable soil contamination. Ash content did not have significant correlation with microbiological quality, although ash is a possible risk factor for hygienic quality. According to the results of this study it is highly important to study the quality of the production chain of bast fibre plants to ensure the quality of industrial products. From the producer's point of view, raw material with defined quality can be directed to the most suitable application. The behaviour of fractions in various ambient atmospheres, and other quality aspects such as hygienic level can be used as criteria for defining the most appropriate product applications.

Arthropod assemblages in vegetative vs. humic portions of epiphyte mats in a neotropical cloud forest

Epiphyte mats (contiguous pieces of live and dead epiphytes perched upon branches of trees) are a conspicuous component of tropical cloud forests and harbor diverse meso- and microarthropod communities. We investigated differences in arthropod assemblage structure between the vegetative (green) and humic (brown) portions of epiphyte mats in a lower montane forest in Monteverde, Costa Rica. Because of qualitative differences between the two substrates, we hypothesized that they would support different arthropod communities and that variation in community parameters would be linked to the quantity of brown material present in a mat sample. The green fraction contained twice as many individuals and species per gram dry mass than the brown fraction. Morphospecies composition was very similar between green and brown portions, but the relative abundance of several taxa differed significantly between the substrates. Contrary to our prediction, total arthropod abundance and richness in a sample were not correlated with the proportion of brown material present. In laboratory trials, the most common morphospecies of oribatid mite in this system showed a preference for brown substrates.

Direct expression of an index for the degree of humification of humic acids using organic carbon concentration

One of the indices for the degree of humification of humic acids, RF, was evaluated in terms of organic C concentration. Thirty-six humic acid samples varying in the degree of humification were analyzed for comparison of the volumes of 0.02 M KMnO4 consumed by humic acid solutions, with their organic C concentration determined using a dissolved C analyzer. A significant correlation (r = 0.981***) was found between them regardless of the degree of humrncation, and RF could be replaced with A 600/C, the absorbance at 600 nm per mg C mL−1 in 0.1 M NaOH, by multiplying by a factor of 0.0648 (r = 0.994***). Accuracy of the organic C concentration of the humic acid solution that was determined using the dissolved C analyzer was confirmed by comparing with the C content determined by the dry-combustion method. Although the organic C concentrations in the humic acid solutions estimated by a colorimetric method with potassium dichromate-sulfuric acid as reagent were significantly lower than those determined using the dissolved C analyzer, the high correlation between them (r = 0.918***) enabled to estimate A 600/C by the colorimetry. In the A 600/C-log (A 400/A 600) (= Δlog K) diagram, A 600/C values of 2.5 and 5.0 could be applied instead of RF values of 40 and 80 as boarders to classify humic acids into lYPes A, B, and Rp. Significant correlations were also found between E 4/E 6 , the ratio of absorbances at 465 and 665 run in 0.025 M NaHC03 , and A 400/A 600 or Δlog K except for a sample containing a high proportion of Pg, the green fraction, which indicated the interchangeability between them with exception. Shortening of the period for extracting humic and fulvic acid fractions without changes in quantity and quality was also examined using four typical Japanese soils. Modification of extraction with standing and intermittent shaking with 0.1 M NaOH at 25°C for 48 h in the present NAGOYA method (Kuwatsuka et al. 1992: Soil Sci. Plant Nutr., 38, 23–30) to continuous shaking under the same conditions enabled to shorten the period of extraction to 24 h. Shorter periods of 4 hand 16 h (overnight) were considered to be insufficient for a Fluvisol containing humic acids with a low degree of humification.

Disponibilidade, composição botânica e valor nutritivo da forragem de pastos consorciados, sob três taxas de lotação

Avaliou-se o efeito de três taxas de lotação, em pastagens de Brachiaria decumbens x Stylosanthes guianensis cv. Mineirão e de B. brizantha cv. Marandu x S. guianensis cv. Mineirão, sobre a disponibilidade, a composição botânica e o valor nutritivo da forragem. Adotou-se o delineamento experimental em blocos casualizados com os tratamentos no esquema de parcelas subdivididas, com duas repetições. Os tratamentos das parcelas constituíram um fatorial 2x3, sendo duas gramíneas (B. decumbens e B. brizantha cv. Marandu) em consorciação com S. guianensis cv. Mineirão e três taxas de lotação (0,8; 1,2 e 1,6 UA/ha), e as subparcelas, as épocas de amostragem (julho e outubro de 1998, correspondendo à época seca; janeiro e abril de 1999, correspondendo à época das águas). Foram utilizados bezerros Nelore, desmamados, com peso vivo médio de 138 kg, no início do experimento. A disponibilidade de matéria seca (MS) da consorciação B. brizantha x Mineirão não variou entre épocas, com valor médio de 3470 kg/ha de MS, enquanto que, para a consorciação B. decumbens x Mineirão, a média para o período das águas (3485 kg/ha de MS) foi superior a do período seco (3056 kg/ha de MS). A disponibilidade da fração verde da gramínea diminuiu com a elevação da taxa de lotação. Durante a época das águas, verificou-se maior proporção de gramínea, em relação à leguminosa, para uma taxa de lotação estimada de 1,17 UA/ha. As pastagens com B. decumbens apresentaram, de modo geral, maior proporção de forragem verde, de melhor valor nutritivo, associado a maior presença de leguminosa do que as pastagens com B. brizantha.

Influence of the Interannual Variability of Vegetation on the Surface Energy Balance—A Global Sensitivity Study

Abstract The degree to which the interannual variability of vegetation phenology affects hydrological fluxes over land is investigated through a series of simulations with the Mosaic land surface model, run both offline and coupled to the NASA Seasonal-to-Interannual Prediction Project (NSIPP) atmospheric general circulation model (GCM). Over a 9-yr period, from 1982 to 1990, interannual variations of global biophysical land surface parameters (i.e., vegetation density and greenness fraction) are derived from Normalized Difference Vegetation Index (NDVI) data collected by the Advanced Very High Resolution Radiometers (AVHRRs). First the sensitivity of evapotranspiration to interannual variations in vegetation properties is evaluated through offline simulations that ignore feedbacks between the land surface and the atmospheric models, and interannual precipitation variations. Evapotranspiration is shown to be highly sensitive to variations in vegetation over wet continental surfaces that are not densely ve...

Gastrectomy in Combination with a Distal Splenorenal Shunt in a Patient with Gastric Cancer and Portal Hypertension: Report of a Case

We describe the case of a patient with gastric cancer complicated by portal hypertension due to liver cirrhosis. Endoscopy showed esophageal varices in the lower third of the esophagus and a superficially depressed lesion in the middle third of the stomach, while a biopsy suggested signet-ring cell carcinoma. Laboratory data showed pancytopenia, the indocyanine green fraction after 15 min was 29%, and the symptoms corresponded to the Child B criteria. A preoperative arteriogram revealed a remarkably dilated left gastric vein and the development of collateral pathways. We performed a distal subtotal gastrectomy with a reconstruction by the Billroth I method combined with a distal splenorenal shunt (DSRS) and a splenopancreatic disconnection (SPD). The endoscopic findings of the esophageal varices 15 months after surgery showed only a few white veins and the red color sign had disappeared. Now 7 years have passed since surgery, the risk of variceal hemorrhage has disappeared, and the patient is ambulatory and well. These results seems to be attributable to the long-term maintenance of the shunt selectivity and good portal hemodynamics. In patients with gastric cancer complicated with esophageal and/or gastric varices, it is recommended that DSRS with SPD be performed after a reconstruction using the Billroth I method.

Inversion of net ecosystem CO2 flux measurements for estimation of canopy PAR absorption

AbstractThe fractional absorption of photosynthetically active radiation (fPAR) is frequently a key variable in models describing terrestrial ecosystem–atmosphere interactions, carbon uptake, growth and biogeochemistry. We present a novel approach to the estimation of the fraction of incident photosynthetically active radiation absorbed by the photosynthetic components of a plant canopy (fChl). The method uses micrometeorological measurements of CO2 flux and incident radiation to estimate light response parameters from which canopy structure is deduced. Data from two Ameriflux sites in Oklahoma, a tallgrass prairie site and a wheat site, are used to derive 7‐day moving average estimates of fChl during three years (1997–1999). The inverse estimates are compared to long‐term field measurements of PAR absorption. Good correlations are obtained when the field‐measured fPAR is scaled by an estimate of the green fraction of total leaf area, although the inverse technique tends to be lower in value than the field measurements.The inverse estimates of fChl using CO2 flux measurements are different from measurements of fPAR that might be made by other, more direct, techniques. However, because the inverse estimates are based on observed canopy CO2 uptake, they might be considered more biologically relevant than direct measurements that are affected by non‐physiologically active components of the canopy. With the increasing number of eddy covariance sites around the world the technique provides the opportunity to examine seasonal and inter‐annual variation in canopy structure and light harvesting capacity at individual sites. Furthermore, the inverse fChl provide a new source of data for development and testing of fPAR retrieval using remote sensing. New remote sensing algorithms, or adjustments to existing algorithms, might thus become better conditioned to ‘biologically significant’ light absorption than currently possible.

大磯丘陵下末吉埋没土層における腐植酸緑色画分Ｐｇの特性と生成環境

The use of humic acid green fraction (Pg) as a paleoenvironmental indicator still requires integrated case studies applied to tephra and loess soil sequences (Watanabe and Kado, 2000; Watanabe et al., 2001a), as well as biochemical studies on humic acid Pg (Watanabe et al., 2001b). The stability and the chemical transformation of humic acid Pg should be elucidated by investigating paleosols and terrestrial deposits.This study aims to clarify the properties of humic acid green fraction Pg in the Shimosueyoshi buried layer (SB layer), the buried humic soil originating from tephra supplies of Hakone Caldera, corresponding to Marine oxygen isotope stage 5e. Pg absorption strength (Pg abs), total carbon content (TC), carbon content of extracted humic acid (CHA), pH (NaF) value, major element compositions, and phytolith analyses, together with selective dissolution of Fe compounds, and color measurement according to CIE color system were conducted. The obtained results were : 1) Clear Pg absorption bands at around 450, 570, and 615 nm were detected from all the humic acid of paleosols, corresponding to > 100 ka, located at Oiso Hill, central Japan. The fluctuation of Pg abs of humic acid in the investigated profile showed a significant increase in the SB layer (ca. 130 ka), equivalent to the early stage of MIOS 5e.2) According to the measurement error of Pg abs determined through the profile, the significant level of Pg abs in this study is confirmed to be much lower than that of Pg abs in previous studies carried on younger tephra soil sequences. It is considered that humic acid Pg is transformed in paleosols over 100 ka.3) Although the relations among amorphous and crystalline iron hydroxides and Pg absorption strength were not clear in this profile, unlike the previous reports (Kawahigashi et al., 1999, Watanabe and Kobayashi, 2001), the SB layer was characterized by the existence of geothite-like iron hydroxides, suggesting a humid environment.

Humus composition of soils under forest, coffee and arable cultivation in hilly areas of south Sumatra, Indonesia

SummaryTo understand the effect of land use changes on the composition of humus in tropical soils, samples from land under primary forest, secondary forest, coffee plantation, and arable crops were investigated at three sites in south Sumatra, Indonesia. Total carbon and total nitrogen contents were 1.7 to 4.3 times and 1.1 to 2.8 times greater in the topsoil under primary forest than under the other types of land use. Following change from primary forest to other uses, the proportion of humic acids in the organic matter of the topsoils decreased while that of the fulvic acid fraction increased. Within the range of land uses, differences in the yields of humic acids and fulvic acid fractions were, respectively, larger and smaller than those in total carbon content. The humic acids were classified into the low and middle classes in the degree of humification. Absorption due to the green fraction of humic acids, Pg, was detected in the UV‐visible spectra of almost all the humic acids. No relation was observed between the degree of humification of humic acids or the strength of Pg absorption in their spectra and land use change. The fulvic acid fractions were fractionated on insoluble polyvinylpyrrolidone (PVP) into the adsorbed fractions consisting of humic substances and the non‐adsorbed fractions consisting of non‐humic substances. A positive correlation between the amount of the fulvic acid fraction and the percentage of the PVP‐adsorbed fraction within it indicated that the variation in the amount of the fulvic acid fraction was attributable to acid‐soluble humic substances. The ionization difference spectra of solutions between pH 12 and pH 7 suggested that the chemical structures of the PVP‐adsorbed fulvic acids have been altered by land use change.

Yield and quality of fertilized deferred forage of Digitaria eriantha and Eragrostis curvula

A cutting experiment was carried out in Bahı́a Blanca (Argentina) during 1998 and 1999 using a randomized block design in a 23factorial experiment: (1) the species Digitaria eriantha and Eragrostis curvula, (2) 0 and 60 kg Nha−1fertilizer treatment and (3) deferred harvesting on 1 June and 15 July. The existing forage was cut in mid-February, the N was distributed and the deferred treatment was initiated. Dry matter yield (DM), dead (DF) and green (GF) fractions, crude protein (CP) content, nitrogen utilization efficiency (NUE), nitrogen recovery (NR) andin vitro DM digestibility (IVDMD) for each year were determined. A treatment by year interaction in DM yields (p<0·05) was found. The deferment date was not found to have any effect (p>0·05). The DM yields were substantially increased by fertilization (p<0·05). Mean DM for the control and the fertilized treatments were 942 and 2430 kg ha−1for D. eriantha and 846 and 1958 kg ha−1for E. curvula, respectively. Similarly, CP for D. eriantha was 5·2 and 6·0%, and 4·2 and 5·2% for E. curvula, respectively. The IVDMD had a small response to the fertilization (p<0·05): the average for D. eriantha was 51% and for E. curvula 39%. The quality of the forage was not influenced by the percentage relationship between DF and GF (p>0·05). The NUE (kg DM kg N−1) and the NR (%) were 24·8 and 25·4 for D. eriantha and 18·6 and 17·6 for E. curvula, respectively. Fertilization must be implemented depending on the costs and the expected increase in income due to the increase in forage production. Marked leaf lodging of D. eriantha may restrict the grazing ability of the animals.

ESTIMATION OF CANOPY PHOTOSYNTHETIC AND NONPHOTOSYNTHETIC COMPONENTS FROM SPECTRAL TRANSMITTANCE

Spectral transmittance signatures (expressed as absorbances) were studied as a potential indicator of photosynthetic and nonphotosynthetic contributions to the canopy-absorbed photosynthetically active radiation (PAR). An analytical approach was made under laboratory conditions using synthetic canopies in an integrating sphere. This approach provided the basis for identifying spectral (absorbance-based) features and indices to estimate green (photosynthetic) and nongreen (structural and dead materials) contributions to canopy absorbance. A strong relationship was found between the amplitude of the first derivative of the absorbance (ARE) and green area, while the integrated absorbance in the PAR region (APAR) mainly responded to variations in total area. The ratio ARE/APAR was closely correlated to the fraction of photosynthetic area to total area (i.e., the canopy green fraction). Similarly, the ratio and normalized difference of the absorbances at 680 and 900 nm (ASR and ANDVI) closely tracked variations in the canopy green fraction. Subsequently, these indices were tested in field plots with contrasting structural characteristics. Under field conditions, ARE was a good indicator of green biomass. The indices ASR and ANDVI were also reliable indicators of green biomass but were affected by changes in sampling conditions. As in the lab study, ARE/APAR was a good indicator of canopy green fraction. Thus, ground-based measurements of canopy spectral transmittance provided a tool for determining the photosynthetic contribution to canopy-absorbed PAR by correcting for nonphotosynthetic canopy components. Moreover, ARE showed a strong correlation with conventional vegetation indices derived from spectral reflectance measurements. This technique could be a useful tool for plant ecophysiology studies and a field-validation method for remote-sensing studies.

Effect of Soil Phosphorus on Leaf Development and Senescence Dynamics of Field‐Grown Maize

Phosphorus deficiency generally decreases plant biomass accumulation by limiting interception of photosynthetically active radiation (PAR) rather than reducing efficiency of conversion of PAR into dry matter. To document the role of P availability in leaf growth and senescence dynamics in maize (Zea mays L.), a 3‐yr field experiment was conducted in southern France with very low, moderate, high, or very high soil test P levels. Leaf appearance rate, individual leaf area, and green fraction changes were recorded at weekly intervals. Rates and duration of expansion and senescence processes were derived independently from fitted logistic functions. Phosphorus deficiency slowed the rate of leaf appearance and reduced the final area of leaves located below the main ear by 18 to 27%, depending on year. The reduction in leaf expansion rates accounted for most of the area reduction over leaf position and years. Senescence rates of the lower leaves were reduced by 29%. The expansion and senescence dynamics of upper leaves were little affected by soil P level. The whole plant peak green leaf area was lower under P‐stressed conditions (16%), and its date of occurrence was significantly delayed (6%). Plant senescence rate was reduced by 15 to 33% during most of the grain filling period. Leaf area duration from emergence to complete senescence was reduced by 13.5%. The early effects of P deficiency on leaf dynamics accounted for most of the 7 to 10% reduction in the amount of absorbed PAR, observed as soon as canopy development allowed maximum light interception.

Equilibrium moisture content of flax/linseed and fibre hemp straw fractions

This preliminary study of the equilibrium moisture content (EMC) of bast fibre plants (Linum usitatissimum L. and Cannabis sativa L.) examines three fractions, fibre, fine shive and coarse shive. The plants were harvested at two times, the first in autumn and the second in spring. The autumn harvest yielded unretted, green material, while the frost-retted material harvested in spring may be classified as overretted. Interesting differences in EMC were found in the dampest air between the two harvest times irrespective of plant species: green fractions were faster to mould at the beginning and lost more weight in the 2-week test period than did the frost-retted samples. The green samples also attained higher EMCs before beginning to mould.

Sequence of electron carriers in the process of methanol oxidation by a new obligate methylotrophic bacterium.

From pink soluble fractions prepared from cells cultured in a copper-free medium, active methanol dehydrogenase (MDH) and two soluble c-type cytochromes (c-I and c-II) were purified homogeneously. The green fractions from cells grown on a medium containing 1.0 mg/l of copper had inactive MDH, cytochrome c-II, and blue copper protein. The amount of copper retained in the blue copper protein increased with cultivation time. The oxidized blue copper protein was similar to the classical type I blue copper proteins since it had the novel absorption peak at 625 nm. However, when the blue protein was reduced with MDH or dithionite, it showed the same spectrum as ferrocytochrome c-I. The isoelectric points of cytochrome c-I, blue copper protein and cytochrome c-II were 9.08, 9.08 and 6.52, respectively. These results suggest that the identity of the purified blue copper protein is cytochrome c-I, and copper ions bind to the cytochrome as methanol is depleted in the culture medium. In addition, MDH activity was not detected at all in the methanol-depleted condition. The data suggest that blue copper protein acts as a negative regulator for MDH. The electrons were transferred as follows: MDH-->cytochrome c-II-->cytochrome c-I (blue copper protein). It was also revealed that the initial 'docking' of MDH and cytochrome c-II is accompanied by electrostatic interactions between lysine or arginine residues on the alpha-subunit of MDH and carboxyl groups on the cytochrome c-II.