Abstract This article aims at finding efficient hyperspectral indices for the estimation of forest sun leaf chlorophyll content (CHL, µg cm leaf − 2 ), sun leaf mass per area (LMA, g dry matter m leaf − 2 ), canopy leaf area index (LAI, m 2 leaf m soil − 2 ) and leaf canopy biomass (B leaf , g dry matter m soil − 2 ). These parameters are useful inputs for forest ecosystem simulations at landscape scale. The method is based on the determination of the best vegetation indices (index form and wavelengths) using the radiative transfer model PROSAIL (formed by the newly-calibrated leaf reflectance model PROSPECT coupled with the multi-layer version of the canopy radiative transfer model SAIL). The results are tested on experimental measurements at both leaf and canopy scales. At the leaf scale, it is possible to estimate CHL with high precision using a two wavelength vegetation index after a simulation based calibration. At the leaf scale, the LMA is more difficult to estimate with indices. At the canopy scale, efficient indices were determined on a generic simulated database to estimate CHL, LMA, LAI and Bleaf in a general way. These indices were then applied to two Hyperion images (50 plots) on the Fontainebleau and Fougeres forests and portable spectroradiometer measurements. They showed good results with an RMSE of 8.2 µg cm − 2 for CHL, 9.1 g m − 2 for LMA, 1.7 m 2 m − 2 for LAI and 50.6 g m − 2 for Bleaf. However, at the canopy scale, even if the wavelengths of the calibrated indices were accurately determined with the simulated database, the regressions between the indices and the biophysical characteristics still had to be calibrated on measurements. At the canopy scale, the best indices were: for leaf chlorophyll content: ND chl  = ( ρ 925  −  ρ 710 )/( ρ 925  +  ρ 710 ), for leaf mass per area: ND LMA  = ( ρ 2260  −  ρ 1490 )/( ρ 2260  +  ρ 1490 ), for leaf area index: D LAI  =  ρ 1725  −  ρ 970 , and for canopy leaf biomass: ND Bleaf  = ( ρ 2160  −  ρ 1540 )/( ρ 2160  +  ρ 1540 ).

Calibration and validation of hyperspectral indices for the estimation of broadleaved forest leaf chlorophyll content, leaf mass per area, leaf area index and leaf canopy biomass

Aluminum (Al) is the most abundant metal in the earth's crust, but its availability depends on soil pH. Despite this abundance, Al is not considered an essential element and so far no experimental evidence has been put forward for a biological role. In plants and other organisms, Al can have a beneficial or toxic effect, depending on factors such as, the concentration of the metal, the chemical form of Al, growth conditions and plant species. Here we review recent advances in the study of Al in plants at physiological, biochemical and molecular levels, focusing mainly on the beneficial effect of aluminum in plants (stimulation of root growth, increased nutrient uptake, the increase in enzyme activity, etc.). In addition, we discuss the possible mechanisms involved in improving the growth of plants cultivated in soils with acid pH, as well as mechanisms of tolerance to the toxic effect of aluminum.

Aluminum, a Friend or Foe of Higher Plants in Acid Soils

Effect of salt stress on phenolic compounds, glucosinolates, myrosinase and antioxidant activity in radish sprouts

Theanine is a non-protein amino acid that occurs naturally in the tea plant (Camellia sinensis) and contributes to the favourable taste of tea. It is also associated with effects such as the enhancement of relaxation and the improvement of concentration and learning ability. It is also linked with health benefits including the prevention of certain cancers and cardiovascular disease, the promotion of weight loss and enhanced performance of the immune system. Thus, there has been a significant rise in the demand for theanine. While theanine has been chemically and biologically synthesised, techniques to isolate theanine from natural sources remain an important area of research. In this review article, the properties and health benefits of theanine are summarised and the synthesis and isolation of theanine are reviewed and discussed. Future perspectives for the isolation of theanine from natural sources are also outlined.

L-Theanine: properties, synthesis and isolation from tea.

The aluminium (Al) cation Al3+ is highly rhizotoxic and is a major stress factor to plants on acid soils, which cover large areas of tropical and boreal regions. Many woody plant species are native to acid soils and are well adapted to high Al3+ conditions. In tropical regions, both woody Al accumulator and non-Al accumulator plants occur, whereas in boreal regions woody plants are non-Al accumulators. The mechanisms of these adaptations can be divided into those that facilitate the exclusion of Al3+ from root cells (exclusion mechanisms) and those that enable plants to tolerate Al3+ once it has entered the root and shoot symplast (internal tolerance mechanisms). The biochemical and molecular basis of these mechanisms have been intensively studied in several crop plants and the model plant Arabidopsis. In this review, we examine the current understanding of Al3+ exclusion and tolerance mechanisms from woody plants. In addition, we discuss the ecology of woody non-Al accumulator and Al accumulator plants, and present examples of Al3+ adaptations in woody plant populations. This paper complements previous reviews focusing on crop plants and provides insights into evolutionary processes operating in plant communities that are widespread on acid soils.

https://www.dora.lib4ri.ch/wsl/islandora/object/wsl%3A3009/datastream/PDF/view

Aluminum exclusion and aluminum tolerance in woody plants.

Chemical forms of aluminum in xylem sap of tea plants (Camellia sinensis L.).

Using spectral reflectance to estimate leaf chlorophyll content of tea with shading treatments

Use of covering cultivation to shade tea (Camellia sinensis L.) trees to produce high-quality, high-priced green tea has recently increased in Japan. Knowledge of shading effects on morphological and color traits and on chemical components of new tea shoots is important for product quality and productivity. We assessed these traits of tea shoots and their relationships under covering cultivation of various radiation intensities.; Results: Leaf thickness, leaf mass per area, and leaf density of new tea leaves were smaller under covering culture than under open-field culture. SPAD values and chlorophyll contents were larger under covering culture than under open culture. The derived exponential equation for estimating chlorophyll contents from SPAD values was improved by considering leaf thickness. Covering culture decreased epicatechin and epigallocatechin contents, and increased theanine and caffeine contents. Principal component analysis on shoot and leaf traits indicated that leaf mass per area, chlorophyll, epicatechin, and epigallocatechin contents were strongly associated with shading effects.; Conclusion: The morphological traits, color traits, and chemical components of new tea shoots and leaves varied depending on radiation intensity, shoot growth, and cropping season. These findings are useful for covering cultivation with high quality and high productivity in tea gardens. © 2018 Society of Chemical Industry.; © 2018 Society of Chemical Industry.

Effect of shading intensity on morphological and color traits and on chemical components of new tea (Camellia sinensis L.) shoots under direct covering cultivation.

Theanine, a major amino acid in green tea, exhibits a stress-reducing effect in mice and humans. Matcha, which is essentially theanine-rich powdered green tea, is abundant in caffeine. Caffeine has a strong antagonistic effect against theanine. The stress-reducing effect of matcha was examined with an animal experiment and a clinical trial. The stress-reducing effect of matcha marketed in Japan and abroad was assessed based on its composition. The stress-reducing effect of matcha in mice was evaluated as suppressed adrenal hypertrophy using territorially-based loaded stress. High contents of theanine and arginine in matcha exhibited a high stress-reducing effect. However, an effective stress-reducing outcome was only possible when the molar ratio of caffeine and epigallocatechin gallate (EGCG) to theanine and arginine was less than two. Participants (n = 39) consumed test-matcha, which was expected to have a stress-reducing effect, or placebo-matcha, where no effect was expected. Anxiety, a reaction to stress, was significantly lower in the test-matcha group than in the placebo group. To predict mental function of each matcha, both the quantity of theanine and the ratios of caffeine, EGCG, and arginine against theanine need to be verified.

https://www.mdpi.com/2072-6643/10/10/1468/pdf

Hideki Horie

Papers

Chemical forms of aluminum in xylem sap of tea plants (Camellia sinensis L.).

Using spectral reflectance to estimate leaf chlorophyll content of tea with shading treatments

Effect of shading intensity on morphological and color traits and on chemical components of new tea (Camellia sinensis L.) shoots under direct covering cultivation.

Stress-Reducing Function of Matcha Green Tea in Animal Experiments and Clinical Trials

Antioxidative effects of daikon sprout (Raphanus sativus L.) and ginger (Zingiber officinale Roscoe) in rats