Towards remote sensing of vegetation processes

The latest advances in imaging spectroscopy of vegetation enabled remote sensing (RS) of plant reflected or emitted signals associated with photosynthetic processes as the photoprotective transformation of xanthophyll pigments or the chlorophyll fluorescence (Chl-F). A potential future European Space Agency (ESA) satellite mission FLEX is expected to sense, apart from other parameters, so-called steady-state chlorophyll fluorescence (Chl-FS) signal, which may be potentially used for monitoring of photosynthesis (vegetation canopy carbon assimilation rate). Nevertheless, geometric complexity of plant canopies and signal disturbing atmospheric factors require a proper approach for scaling the information of a single leaf optical properties up to the RS image data of anisotropic vegetation canopies. Such up-scaling approach can be established only via synergic measurements of ground based and air-/space-borne optical sensors. Our initial experiment revealed that Chl-FS, being strongly driven by the air temperature, is able to accurately indicate onset and off-set of the photosynthetically active period for the evergreen plants. Next field experiment, carried out with the VNIR imaging spectroradiometer AISA Eagle (SPECIM Ltd., Finland) mounted above the montane grassland and Norway spruce (Picea abies /L./ Karst.) canopies, showed that the fluorescence signal is retrievable from passive optical imaging spectroscopy data. Further analyses revealed that some of the vegetation \u27process-related\u27 optical indices (e.g., photochemical reflectance index - PRI) are closely correlated to the parameters measured over the experimental canopies by eddy-covariance flux systems. The future objective is to continue in development the leaf-canopy Chl-F up-scaling approach by setting up local scale experiments employing the field pocket-size cost effective instruments measuring the leaf optical indices and Chl-F parameters simultaneously with canopy reflectance acquired by RS sensors from tower and aircraft platforms

Hodnoceni udrzitelnosti zemedelskeho hospodareni.

Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

Role of <i>Litsea cubeba</i> Essential Oil in Agricultural Products Safety: Antioxidant and Antimicrobial Applications

The essential oil from Litsea cubeba (LCEO) has good antioxidant, antimicrobial, anti-insect properties, which gives it the potential for use as a natural additive to food resources and food products in order to prevent spoilage and extend shelf life. In this study the biological activity related to food preservation was observed. The main volatile organic compounds were geranial (39.4%), neral (29.5%), and limonene (14.3%). Antioxidant activity was 30.9%, which was equal to 167.94 µg of Trolox per mL of sample. Antimicrobial activity showed the strongest inhibition against Serratia marcescens by disk diffusion method and minimum inhibitory concentrations MIC 50 and MIC 90 were the lowest for Micrococcus luteus with values 1.46 and 3.52 µL/mL, respectively. Antimicrobial activity of the LCEO vapor phase showed strong inhibition of microorganisms on apples, pears, potatoes, and kohlrabies. Over 50% of gram-positive and gram-negative bacteria and yeasts were inhibited by a concentration of 500 µL/mL. The inhibition of microorganisms was concentration dependent. Anti-insect activity was also strong, with 100% lethality of Pyrrhocoris apterus at a concentration of 25%. These results suggest that LCEO could be potentially used as a food preservative

The Potential Use of <i>Citrus aurantifolia</i> L. Essential Oils for Decay Control, Quality Preservation of Agricultural Products, and Anti-Insect Activity

The primary objective of the study was to evaluate the biological activity of Citrus aurantifolia essential oil (CAEO) with emphasis on antioxidant, antimicrobial, and insecticidal activity, chemical composition, and the antimicrobial effect of its vapor phase in situ on various food models. We determined the main volatile components of CAEO as α-phellandrene (48.5%) and p-cymene (16.5%). The antioxidant activity was high and reached 74.5 ± 0.5%, which corresponds to 442 ± 2.3 TEAC. The antimicrobial activity in the contact phase was most pronounced against Gram-negative bacteria, with inhibition zones of 12.66–15.33 mm and a minimal inhibition concentration of 2.36–8.26 µL/mL. The antimicrobial activity of the CAEO vapor phase was high at the highest concentration tested (500 µL/mL), but the inhibitory effect was seen at all concentrations tested. The effect was observed on all types of microorganisms and all types of model foods. Based on the findings, CAEO could find use in storing and extending the shelf life of agricultural products. Insecticidal activity reached 10–90% depending on the concentration used. The significant insecticidal effect provides the possibility of using CAEO as a natural insecticidal, larvicidal, or repellent preparation

Assessment of <i>Ocimum basilicum</i> Essential Oil Anti-Insect Activity and Antimicrobial Protection in Fruit and Vegetable Quality

Basil (Ocimum basilicum) is a commonly used herb; it also contains essential oils and other valuable compounds. The basil oil obtained has a pleasant aroma, but also a broad spectrum of biological activity. This work reports on the chemical composition, antioxidant, antimicrobial and anti-insect activity in vitro and in situ of Ocimum basilicum essential oil (OBEO) obtained by steam distillation of fresh flowering plants. Gas chromatography–mass spectrometry, DPPH, agar and disc diffusion and vapor phase methods were used to analyze the OBEO properties. The analysis of the chemical composition of OBEO showed that its main components were methyl chavicol (88.6%), 1,8-cineole (4.2%) and α-trans-bergamotene (1.7%). A strong antioxidant effect was demonstrated at the level of 77.3%. The analysis of antimicrobial properties showed that OBEO exerts variable strength of inhibiting activity against various groups of microorganisms. The growth inhibition zones ranged from 9.67 to 15.33 mm in Gram-positive (G+) and Gram-negative (G−) bacteria and from 5.33 to 7.33 mm in yeast. The lowest measured minimal inhibition concentration (MIC) was 3.21 µL/mL against Gram-negative Azotobacter chrococcum and Gram-positive Micrococcus luteus. The antimicrobial activity of in situ vapor phase of OBEO was also confirmed on apples, pears, potatoes and kohlrabi. The highest insecticidal activity against Pyrrhocorisapterus, observed at the concentration of 100%, caused the death of 80% of individuals. Due to its broad spectrum of activity, OBEO seems an ideal candidate for preserving fruit and vegetables

Assessment of Ocimum basilicum Essential Oil Anti-Insect Activity and Antimicrobial Protection in Fruit and Vegetable Quality

Basil (Ocimum basilicum) is a commonly used herb; it also contains essential oils and other valuable compounds. The basil oil obtained has a pleasant aroma, but also a broad spectrum of biological activity. This work reports on the chemical composition, antioxidant, antimicrobial and anti-insect activity in vitro and in situ of Ocimum basilicum essential oil (OBEO) obtained by steam distillation of fresh flowering plants. Gas chromatography&ndash;mass spectrometry, DPPH, agar and disc diffusion and vapor phase methods were used to analyze the OBEO properties. The analysis of the chemical composition of OBEO showed that its main components were methyl chavicol (88.6%), 1,8-cineole (4.2%) and &alpha;-trans-bergamotene (1.7%). A strong antioxidant effect was demonstrated at the level of 77.3%. The analysis of antimicrobial properties showed that OBEO exerts variable strength of inhibiting activity against various groups of microorganisms. The growth inhibition zones ranged from 9.67 to 15.33 mm in Gram-positive (G+) and Gram-negative (G&minus;) bacteria and from 5.33 to 7.33 mm in yeast. The lowest measured minimal inhibition concentration (MIC) was 3.21 &micro;L/mL against Gram-negative Azotobacter chrococcum and Gram-positive Micrococcus luteus. The antimicrobial activity of in situ vapor phase of OBEO was also confirmed on apples, pears, potatoes and kohlrabi. The highest insecticidal activity against Pyrrhocorisapterus, observed at the concentration of 100%, caused the death of 80% of individuals. Due to its broad spectrum of activity, OBEO seems an ideal candidate for preserving fruit and vegetables