Intrinsic UV reflection and fluorescence studies for water sorption in polycarbonate, polyurethane and poly(ethylene terephthalate) films

Intrinsic UV reflection and fluorescence behaviors of polycarbonate, polyurethane and poly(ethylene terephthalate) films were investigated in order to characterize the interaction of water in these films. During water sorption process, UV reflection spectra of polycarbonate and polyurethane films showed little peak position changes. Fluorescence emission spectra of polycarbonate films showed red spectral shifts from 332 nm with water immersion time. This red-shifted peak could be due to phenyl-2-phenoxybenzoate, which is one of the major thermal degradation products in polycarbonate. Fluorescence peaks of polyurethane films appeared at two different positions and the ratio of these peak intensities increased with increasing immersion time. In the case of PET films, the UV reflection spectrum showed the peak intensity around 340 nm to change in response to water sorption. The fluorescence near 388 nm probably due to ground state dimer exhibited sensitivity with water sorption, when excited at 340 nm.     

Description of batter mixing using near infrared spectroscopy

The aim of the present study was to describe the physicochemical events occurring during batter mixing at different water contents (51.8, 54.4, and 56.7 g of water/100 g of dough) using near infrared (NIR) spectroscopy. An FT-NIR spectrometer over the 1000–2500 nm range with a fibre optic probe was used to record NIR spectra in-line. The analysis of both one-dimensional statistical method (principal components analysis) and two-dimensional statistical methods (generalised two-dimensional correlation spectroscopy) was conducted to evaluate the possibilities of NIR spectroscopy to monitor physical and physicochemical modifications observed during mixing of batter. The NIR results were in agreement with the physical and physicochemical analysis traditionally used to study bread dough mixing (consistency and glutenin depolymerisation). PCA on raw NIR spectra demonstrated that PC₁ describes the same traces as the dough consistency curves. PCA on raw NIR spectra can be used to monitor the batter mixing and to identify the NIR mixing time close to the t_peak.PCA on spectra after second derivative demonstrated that PC₁ and PC₂ traces described different traces compared to the dough consistency curves. The loading spectra associated to PC₁ and PC₂ suggested that almost the same physicochemical and chemical mechanisms occur during the dough mixing at 51.8 or 54.4% water contents, but with kinetic and intensity differences. The 2D COS method allowed a sequence of chemical events occurring during mixing for the batters at 51.8 and 54.4% water contents to be tentatively proposed. The 2D COS did not give clear physicochemical differences between the three batters during mixing. The NIR results for the highly hydrated batter (56.7%) were difficult to analyse due to its high water content.     

Description of batter mixing using near infrared spectroscopy

The aim of the present study was to describe the physicochemical events occurring during batter mixing at different water contents (51.8, 54.4, and 56.7 g of water/100 g of dough) using near infrared (NIR) spectroscopy. An FT-NIR spectrometer over the 1000–2500 nm range with a fibre optic probe was used to record NIR spectra in-line. The analysis of both one-dimensional statistical method (principal components analysis) and two-dimensional statistical methods (generalised two-dimensional correlation spectroscopy) was conducted to evaluate the possibilities of NIR spectroscopy to monitor physical and physicochemical modifications observed during mixing of batter. The NIR results were in agreement with the physical and physicochemical analysis traditionally used to study bread dough mixing (consistency and glutenin depolymerisation). PCA on raw NIR spectra demonstrated that PC₁ describes the same traces as the dough consistency curves. PCA on raw NIR spectra can be used to monitor the batter mixing and to identify the NIR mixing time close to the t_peak.PCA on spectra after second derivative demonstrated that PC₁ and PC₂ traces described different traces compared to the dough consistency curves. The loading spectra associated to PC₁ and PC₂ suggested that almost the same physicochemical and chemical mechanisms occur during the dough mixing at 51.8 or 54.4% water contents, but with kinetic and intensity differences. The 2D COS method allowed a sequence of chemical events occurring during mixing for the batters at 51.8 and 54.4% water contents to be tentatively proposed. The 2D COS did not give clear physicochemical differences between the three batters during mixing. The NIR results for the highly hydrated batter (56.7%) were difficult to analyse due to its high water content.     

Application of two-dimensional cross-correlation spectroscopy to analyse infrared (MIR and NIR) spectra recorded during bread dough mixing

During dough mixing chemical, biochemical and physical transformations occur that allow dough formation to be characterized by common chemical and biochemical methods. Recently, spectrometric methods were used to characterize the dough mixing. The Mid-infrared (MIR) and the Near-infrared (NIR) spectroscopy allow information concerning chemical content and composition of food products to be obtained. The aim of this study is to apply FT-NIR and FT-MIR spectroscopy to monitor dough chemical changes, and to correlate those signals by the 2D Cross-Correlation (2D CORR) method. The 2D CORR was used to emphasize chemical assignment of the NIR band modifications (particularly for protein) during dough mixing.The 2D CORR analysis of the raw NIR and MIR spectra demonstrated that five NIR regions are highly correlated to protein vibrations. The 2D CORR analysis of the NIR and MIR spectra after second derivative demonstrated that the amide bands present high R² for the NIR bands at (1189–1216), (1351–1474) and (1873) nm. A low R² is obtained between the amide I and amide II bands and the (2026–2123) and (2280–2325) nm regions. The amide III band presents a slightly higher R² for those NIR regions.The 2D CORR analysis of NIR and MIR spectra allow more specific NIR regions associated to chemical modifications of protein structure to be identified. The 2D CORR analysis of the second derivative spectra is more precise for the identification of the NIR regions implied in dough mixing compared to the 2D CORR analysis of raw NIR and MIR spectra.     

Application of two-dimensional cross-correlation spectroscopy to analyse infrared (MIR and NIR) spectra recorded during bread dough mixing

During dough mixing chemical, biochemical and physical transformations occur that allow dough formation to be characterized by common chemical and biochemical methods. Recently, spectrometric methods were used to characterize the dough mixing. The Mid-infrared (MIR) and the Near-infrared (NIR) spectroscopy allow information concerning chemical content and composition of food products to be obtained. The aim of this study is to apply FT-NIR and FT-MIR spectroscopy to monitor dough chemical changes, and to correlate those signals by the 2D Cross-Correlation (2D CORR) method. The 2D CORR was used to emphasize chemical assignment of the NIR band modifications (particularly for protein) during dough mixing.The 2D CORR analysis of the raw NIR and MIR spectra demonstrated that five NIR regions are highly correlated to protein vibrations. The 2D CORR analysis of the NIR and MIR spectra after second derivative demonstrated that the amide bands present high R² for the NIR bands at (1189–1216), (1351–1474) and (1873) nm. A low R² is obtained between the amide I and amide II bands and the (2026–2123) and (2280–2325) nm regions. The amide III band presents a slightly higher R² for those NIR regions.The 2D CORR analysis of NIR and MIR spectra allow more specific NIR regions associated to chemical modifications of protein structure to be identified. The 2D CORR analysis of the second derivative spectra is more precise for the identification of the NIR regions implied in dough mixing compared to the 2D CORR analysis of raw NIR and MIR spectra.     

Water vapor transport parameters of a cast wheat gluten film

Understanding the mode of transport of water vapor through the film is important for improving the moisture barrier properties of wheat gluten (WG) films. Effective permeability (P_eff), solubility (S_eff), and diffusion (D_eff) coefficients of a hydrophilic cast WG film were determined at 25°C within the relative humidity (RH) range of 0–84% (with a 9–13% RH gradient between upstream and downstream water vapor flux). P_eff, S_eff, and D_eff increased substantially as the RH gradient moved upwards in the RH spectrum. P_eff increased by four orders of magnitude from the lowest RH condition of 0–11% (3.8×10⁻¹¹ g·m/m²·s·Pa) to the highest RH condition of 75–84% (4.1×10⁻⁷ g·m/m²·s·Pa). A moisture sorption isotherm of the film at 25°C was constructed. Both the Guggenheim–Anderson–DeBoer (GAB) and the Kuhn moisture sorption isotherm models showed a good fit to the experimental adsorption data. Testing of WG films at the expected conditions of actual use is necessary to quantify the water vapor permeation through the films.     

Physico-chemical description of bread dough mixing using two-dimensional near-infrared correlation spectroscopy and moving-window two-dimensional correlation spectroscopy

NIR spectroscopy presents a huge interest in exploring chemical changes during dough mixing. The aim of the present study is to investigate the potential of 2D correlation spectroscopy (2D COS) and moving-window 2D (MW2D) correlation spectroscopy to explore the time dependence of NIR spectral responses during wheat flour dough mixing. NIR spectra were continuously recorded (between 1400 and 2325 nm) during mixing of bread type-dough (based on flour, water and yeast), using an FT-NIR spectrometer with a deported probe. The probe was positioned inside the mixer in contact with the dough. The 2D spectra calculated using raw and second derivative NIR spectra were interpreted in terms of physico-chemical events. Nine different industrial flours were used as raw material to validate the analysis. The results obtained using the 2D COS and the MW2D methods give the possibility to ascribe chemical vibrations (starch, water and gluten) to NIR absorbance changes occurring during dough mixing. The analysis of the NIR spectra identified wavelength shift associated to both dough “free water” and protein secondary structure modifications. During this study, only the MW2D method allowed to identify clearly the time dependence of physico-chemical mechanisms from NIR variation bands.     

Characterization of anatomy, ultrastructure and lignin microdistribution in Forsythia suspensa

Forsythia suspensa, as a traditional Chinese medicinal herb, has been studied extensively. In this work, morphological and anatomical features of F. suspensa stem were examined by light microscopy (LM) and scanning electron microscopy (SEM). The results showed that the slenderness and Runkel ratio is 51 and 0.67, respectively. Anatomical observations indicated that F. suspensa is diffuse-porous wood. Helical thickenings and alternate intervessel pits are present on vessel cell wall. Transmission electron microscopy (TEM) images exhibited that the fiber cell wall is typically differentiated into three layers: middle lamella (ML), primary wall (P) and secondary wall (S₁, S₂ and S₃), and the staining intensities represent differing lignin concentrations. Also, the confocal laser scanning microscopy (CLSM) and scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDXA) were used to investigate the lignin distribution in cell wall qualitatively and semi-quantitatively. Confocal images (488 nm) revealed a high level of lignin autofluorescence in the cell corner middle lamella (CCML), with lower levels of fluorescence in the compound middle lamella (CML) and S₂ region. The results from SEM-EDXA demonstrated that lignin concentration ratio in different regions of fiber wall is 1.3 (CCML):1.1 (CML):1 (S₂).     

Assessing newly developed and published vegetation indices for estimating rice leaf nitrogen concentration with ground- and space-based hyperspectral reflectance

Non-destructive and quick assessment of leaf nitrogen (N) status is important for dynamic management of nitrogen nutrition and productivity forecast in crop production. This research was undertaken to make a systematic analysis on the quantitative relationship of leaf nitrogen concentrations (LNCs) to different hyperspectral vegetation indices with multiple field experiments under varied nitrogen rates and varied types in rice (Oryza sativa L.). The results showed that some published indices had good relations with LNC such as two-band indices, R₇₅₀/R₇₁₀ (ZM), Gitelson and Merzlyak index two (GM-2), R₇₃₅/R₇₂₀ (RI-1dB), R₇₃₈/R₇₂₀ (RI-2dB) and the normalized difference red edge index (NDRE), three-band indices, adjusted normalized index 705 (mND705), physiological reflectance index c (PRI_c), terrestrial chlorophyll index (MTCI), and red edge position derived with four point linear interpolation (REP_LI). Three-band indices performed better than two-band indices, with MTCI exhibiting the best logarithmic relation to LNC in rice. Then, hyper-spectral vegetation indices computed with random two bands (λ₁ and λ₂) from 400 to 2500 nm range were related to LNC of rice. The results indicated that two-band indices combined with bands of 550–600 nm and 500–550 nm in green region had good relationships with LNC, and simple ratio index SR(533,565) performed the best in all two-band indices, similar to the published three-band indices (mND705, PRI_c and MTCI). New three-band indices R₄₃₄/(R₄₉₆ + R₄₀₁) and R₇₀₅/(R₇₁₇ + R₄₉₁) were proposed for prediction of LNC with improved ability over the SR(533,565) and published spectral indices. Moreover, R₇₀₅/(R₇₁₇ + R₄₉₁) performed well in all the data from ground spectra, modeled AVIRIS and Hyperion spectra, and acquired Hyperion image hyperspectra. The R₄₃₄/(R₄₉₆ + R₄₀₁) also exhibited well in both ground and modeled AVIRIS and Hyperion image spectra, but could not be tested with the acquired Hyperion image because of the absence in radiometric calibration of the bands less than 416 nm. Overall, the newly developed three-band spectral index R₇₀₅/(R₇₁₇ + R₄₉₁) should be a good indicator of LNC at ground and space scales in rice. Yet, these new indices still need to be tested with more remote sensors based on ground, airborne and spaceborne, and verified widely in other ecological locations involving different cultivars and production systems.     

Extracellular production of silver nanoparticles by using three common species of dermatophytes: Trichophyton rubrum, Trichophyton mentagrophytes and Microsporum canis

Background: To develop a new green approach for biosynthesis of silver nanoparticles, myconanotechnology has been represented as a novel field of study in nanotechnology. In this study, we have reported the extracellular synthesis of highly stable silver nanoparticles using three species of dermatophytes: Trichophyton rubrum, Trichophyton mentagrophytes and Microsporum canis. Methods: Clinical strains of these species were grown in a liquid medium containing mineral salt and incubated at 25°C for 5-7 days. The cell-free filtrate of each culture was obtained and subjected to synthesize silver nanoparticles in the presence of 1 mM AgNO₃. Results: The reduction of Ag+ ions in metal nanoparticles was investigated virtually by tracing the solution color which was switched into reddish-light brown after 72 h. For T. mentagrophytes, a UV-visible spectra demonstrating a strong, quite narrow peak located between 422 and 425 nm was obtained. For M. canis, a fairly wide peak centering at 441 nm and for T. rubrum, a weak spectrum to decipher were observed. According to transmission electron microscopy (TEM) results, fairly uniform, spherical, and small in size with almost less than 50 nm particles were forms in case of T. mentagrophytes. For the other two species, TEM images showed existence of small spherical nanosilvers but not as small as nanoparticles synthesized by T. mentagrophytes. Conclusion: We observed that species belong to a single genus of the fungi have variable ability to synthesize silver nanoparticles extracellulary with different efficiency. Furthermore, the extracellular synthesis may make the process simpler and easier for following processes.Key Words: Nanoparticles, Dermatophytes, Extracellular biosynthesis     

Detection of powdery mildew in two winter wheat cultivars using canopy hyperspectral reflectance

To determine the most sensitive spectral parameters for powdery mildew detection, hyperspectral canopy reflectance spectra of two winter wheat cultivars with different susceptibilities to powdery mildew were measured at Feekes growth stage (GS) 10, 10.5, 10.5.3, 10.5.4 and 11.1 in 2007–2008 and 2008–2009 seasons. As disease indexes increased, reflectance decreased significantly in near infrared (NIR) regions and it was significantly correlated with disease index at GS 10.5.3, 10.5.4 and 11.1 for both cultivars in both seasons. For the two cultivars, red edge slope (dr_red), the area of the red edge peak (Σdr_{680−760 nm}), difference vegetation index (DVI) and soil adjusted vegetation index (SAVI) were significantly negatively correlated with disease index at GS 10.5.3, 10.5.4 and 11.1 in both seasons. Compared with other parameters, Σdr_{680−760 nm} was the most sensitive parameter for powdery mildew detection. The regression models based on Σdr_{680−760 nm} were constructed at GS 10.5.3, 10.5.4 and 11.1 in both seasons. These results indicated that canopy hyperspectral reflectance can be used in wheat powdery mildew detection in the absence of other stresses resulting in unhealthy symptoms. Therefore, disease management strategies can be applied when it is necessary based on canopy hyperspectral reflectance data.     

Water Sorption and Dielectric Relaxations of Wheat Dough (Containing Sucrose, NaCl, and their Mixtures)

Dielectric relaxations of wheat doughs with different water contents and effects of sucrose, NaCl, and their mixture on relaxation temperatures were investigated using dielectric analysis (DEA). All ingredients were dissolved in distilled water used to prepare wheat flour doughs to optimum consistency. Before analysis, samples were stored at room temperature in vacuum desiccators over a_w range of 0·225–0·753. Dynamic DEA measurements were made at a heating rate of 2 °C/min from 40 °C below and above the observed relaxation zone. The frequencies used were 0·1, 0·5, 1, and 5 Hz. Steady state water contents varied from 3·21 to 10·89 g H₂O/100 g dm over a_w range used for the plain dough (flour+water). Added ingredients increased sorption of doughs. The tan δ of DEA showed an α-relaxation (glass transition) in all doughs at all frequencies used. The relaxation peak temperature, taken as T_g, increased with increasing frequency. Added sucrose decreased the T_g of doughs, as well as added NaCl. A dramatic depressing effect of NaCl on T_g was probably due to an increase in conductivity of doughs.     

Phenological variations,yield differences and free proline accumulation in rice under alternate inundation and suspension of irrigation in Central Thailand

Pot and field experiments were conducted to investigate the phenological and physiological adjustments, yield performance and water productivity of rice under variable periods of suspension of irrigation. Four different water management schedules [viz. conventional water management (CWM), 2-week inundation followed by 2-week suspension of irrigation (I₂ S₂), 1-week inundation followed by 3-week suspension of irrigation (I₁ S₃), and 1-week inundation followed by 4-week suspension of irrigation (I₁ S₄)] were evaluated in greenhouse pots with transplanted rice. Only CWM, I₂ S₂, and I₁ S₃ were tested under field conditions. In the greenhouse pot experiment, the commencement of flowering and physiological maturity of rice occurred in the shortest period with CWM, and delayed with increasing the period of suspension of irrigation during vegetative phase. Some of shoot and root growth parameters of rice had significant differences among different water management practices. Free proline accumulated in leaves was lowest in CWM, increased with increasing the period of suspension of irrigation. The I₁ S₃ water management reported highest water productivity. Field experiment conducted, confirmed the results observed in the greenhouse experiment showing similar pattern of shoot and root growth characteristics and free proline accumulation in rice plants. The water productivity and grain yield was significantly higher in I₂ S₂ over CWM and I₁ S₃. Overall results suggest that the 2-week inundation followed by 2-week suspension of irrigation water management is a better option for water saving with higher yield in transplanted rice for 120 days old Suphan Buri 1 hybrid in Central Thailand.     

Selection against inbred seedlings in mixtures of inbred and hybrid true potato seed

Summary The effect of selection against weak plants was studied in artificial mixtures of hybrid (S₀), first self-pollinated generation (S₁), and second self-pollinated generation (S₂), true potato seed. Selection of vigorous seedlings in true seed populations raised in flats from mixtures of S₀ (25%), S₁ (50%), and S₂ (25%) seed increased the frequency of hybrids to 71%. In another study, two mixtures of S₀ and S₁ seed (1∶3 and 1∶1) were densely sown in beds to produce seedling tubers. Elimination of weak plants during population thinning and subsequent interplant competition significantly reduced the frequency of inbred plants. The resulting seedling tuber progenies were planted in the field and mean yields from the two mixtures of S₀ and S₁ seed were 96% and 99% of related completely hybrid progenies. The implications of these results for TPS production are discussed.     

缺素对小麦冠层反射光谱的影响

为给小麦缺素症早期诊断提供依据,以太湖地区典型稻麦轮作区的长期定位施肥实验为研究对象,分析了氮磷钾单一营养元素缺乏和两种或两种以上元素同时缺乏时的小麦叶绿素含量（SPAD值）及冠层反射光谱特性的变化规律。结果表明,缺素造成了叶片叶绿素含量的下降。缺氮使小麦冠层光谱反射率在可见光波段（460～710nm）和1480～1650nm波段增加,在近红外波段（760～1220nm）下降,红光波段对胁迫表现最为敏感．其次为黄光波段和1480nm左右的水分吸收波段;缺磷降低了近红外波段反射率,对可见光波段反射率的影响则受生育阶段和其他肥料互作的影响;缺钾处理对冠层反射光谱的影响较小,差异不显著。氮胁迫对可见光波段的影响程度显著高于磷胁迫,近红外波段两者持平。光谱对养分胁迫的响应程度随生育进程的推进而逐渐减小。缺素均使冠层光谱的红边位置向短波方向移动即发生蓝移,位移大小依元素缺乏种类及数量而定,最大位移可达10nm左右。     

Application of Bradyrhizobium japonicum and Phosphorus Fertilization Improved Growth,Yield and Nodulation of Soybean in the Sub-humid Hilly Region of Azad Jammu and Kashmir,Pakistan

Two separate experiments (pot and field) were conducted to examine the response of soybean to Bradyrhizobium japonicum and phosphorus (P) fertilization. Different treatments were i) Rhizobium strains (0, S377, S379, and the mixture of S377 + S379 i.e. S₀, S₁, S₂, S₃); ii) phosphorus (field only, 0, 50, 100 kg ha-¹i.e. T₀, T₁, T₂) and iii) two soils (pot only) i.e. autoclaved (A₁) and non-autoclaved (A₀). A soybean cultivar NARC-1 was tested for estimating growth traits, nodule number and mass, root development and yield traits. In the pot experiment, total number of nodules both in the A₀ and A₁ were negligible but increased significantly following the application of Bradyrhizobium japonicum. In the field experiment, number of nodules increased from 6 in the control treatment without strains to a maximum of 86 in S₃T₁. Shoot dry weight increased significantly from 11.8 g plant-¹ in the control soil to 15.6 g plant-¹ in S₃T₁. Root length was increased but root mass was unaffected. Soybean seed yields ranged between 615 and 1003 kg ha-¹ against 543 kg ha-¹ in the control soil indicating a maximum of 85% increase over control. Shoot dry weight and seed yield had significant correlation with nodulation (R² = 0.91). The results of experiments revealed significant positive effects of rhizobium inoculation and P fertilization on growth, nodulation and yield of soybean and, generally, mixture of strains (S₃) was more effective than the strains S₁ and S₂. Results also indicated that high application of P (100 kg P₂O₅ ha-¹) reduced the efficiency of inoculants for nodule mass and seed yield.     

Dynamic water vapour sorption in gluten and starch films

Water sorption of gluten and wheat starch films as a function of water activity was studied using gravimetric step-change sorption experiments. Films of different thicknesses were used with the aim to vary the characteristic diffusion time and to get insights in the contribution of the polymer-chain rearrangement in the sorption behaviour. It is shown that both starch and gluten are in the glassy state for a water activity a_w below 0.9. From comparison of the dynamical sorption curves with a Fickian diffusion model, it is shown that water diffusion in gluten films seems Fickian for a_w < 0.7, and non-Fickian for a_w > 0.7, while for starch films, non-Fickian sorption behaviour is observed for a_w > 0.1. The results show that polymer-chain rearrangement and the stress built up in the matrix play an important role in the sorption dynamics of these films. Even when the material is in the glassy state matrix relaxation phenomena play a role in the sorption behaviour of starch and gluten.     

Synthesis of Bioactive Silver Nanoparticles Using New Bacterial Strains from an Antarctic Consortium

In this study, we report on the synthesis of silver nanoparticles (AgNPs) achieved by using three bacterial strains Rhodococcus, Brevundimonas and Bacillus as reducing and capping agents, newly isolated from a consortium associated with the Antarctic marine ciliate Euplotes focardii. After incubation of these bacteria with a 1 mM solution of AgNO₃ at 22 °C, AgNPs were synthesized within 24 h. Unlike Rhodococcus and Bacillus, the reduction of Ag⁺ from AgNO₃ into Ag⁰ has never been reported for a Brevundimonas strain. The maximum absorbances of these AgNPs in the UV-Vis spectra were in the range of 404 nm and 406 nm. EDAX spectra showed strong signals from the Ag atom and medium signals from C, N and O due to capping protein emissions. TEM analysis showed that the NPs were spherical and rod-shaped, with sizes in the range of 20 to 50 nm, and they were clustered, even though not in contact with one another. Besides aggregation, all the AgNPs showed significant antimicrobial activity. This biosynthesis may play a dual role: detoxification of AgNO₃ and pathogen protection against both the bacterium and ciliate. Biosynthetic AgNPs also represent a promising alternative to conventional antibiotics against common nosocomial pathogens.     

Quantification of fructan concentration in grasses using NIR spectroscopy and PLSR

Near-infrared reflectance (NIR) spectroscopy combined with chemometrics was used to quantify fructan concentration in samples from seven grass species. Savitzky–Golay first derivative with filter width 7 and polynomial order 2 with mean centering was applied as a spectral pre-treatment method to remove unimportant baseline signals. In order to model the NIR spectroscopy data the partial least squares regression (PLSR) approach was used on the full spectra. Variable selection based on PLSR by jack-knifing within a cross-model validation (CMV) framework was applied in order to remove non-relevant spectral regions. PLSR was also used to model fructan concentrations from an augmented matrix [X|G], where X is spectra and G is correlation matrix of band specific information and X, in order to integrate the chemical band information in regression models. The present analysis showed that rapid quantification of fructans by NIR spectroscopy is possible and that jack-knifing PLSR within a CMV framework is an effective way to eliminate the wavelengths of no interest. Jack-knifing PLSR did not improve the predictive ability because the root mean square error of prediction (RMSEP) increased (1.37) compared to the full model (1.26). This was possibly due to signals from carbohydrates, which could act as cofactor in the prediction of fructans. However, jack-knifing PLSR within a CMV framework simplified the interpretation of the regression model with r² = 0.90 and RMSEP = 1.37.     

Effects of drought on chlorophyll fluorescence in potato (Solanum tuberosum L.). I. Plant water status and the kinetics of chlorophyll fluorescence

Summary The slow kinetics of chlorophyll fluorescence were examined in seven potato genotypes grown either fully irrigated or droughted from the time of plant emergence. Constant and variable fluorescence (F _o andF _v respectively) declined with time in plants from both irrigated and droughted treatments, but the decline was greater in droughted than irrigated plants. However, the yield of variable fluorescence (F _v/(F _o+F _v)) was unaffected by the drought treatment. The main effect of drought was upon the quenching of variable fluorescence. Both the half life of the decay of variable fluorescence (q_1/2) and the secondary maximum (M) were significantly greater in the droughted plants than in those from the irrigated treatment. Significant differences between genotypes were found forF _v/(F _o+F _v),M andq _1/2. Genotype-by-treatment interactions were non-significant for all the variables examined. Changes in chlorophyll fluorescence transients were not closely related to changes in leaf water potential.