DETERMINATION OF L-ARGININE CONTENT IN SCOTS PINE NEEDLES USING THE SAKAGUCHI TEST

Arginine can be accumulated in substantial amounts in coniferous plants whose mineral nutrition is regulated. A simple, quick, accurate and inexpensive method for determining the amino acid in coniferous plant organs is needed to improve the technique of raising the arginine level in the plants and making arginine-rich products of their needles. The aim of this study was to modificate a spectrophotometric method for determining arginine in Pinus sylvestris L. needles containing low or abnormally high levels of the amino acid using the Sakaguchi test. Our studies revealed the agents providing for maximum extraction of arginine from needles. Techniques for stripping the extract of organic compounds and chromogenic reagents for the Sakaguchi test were tested, and the wavelengths of maximum optical absorption of solvents in needle arginine content spectrophotometric analysis were determined. This method is simple, reproducible, accurate, and can be employed to quickly analyze pine needles for arginine content, in particular when developing techniques for augmenting it in coniferous plants and making arginine-rich products of coniferous needles.

Evaluating the performance of a double integrating sphere in measurement of reflectance, transmittance, and albedo of coniferous needles

Leaf reflectance and transmittance spectra are essential information in many applications such as developing remote sensing methods, computing shortwave energy balance (albedo) of forest canopies, and monitoring health or stress of trees. Measurement of coniferous needle spectra has usually been carried out with single integrating spheres, which has involved a lot of tedious manual work. A small double integrating sphere would make the measurements considerably faster, because of its ease of operation and small sample sizes required. Here we applied a compact double integrating sphere setup, used previously for measurement of broad leaves, for measurement of coniferous needles. Test measurements with the double integrating sphere showed relative underestimation of needle albedo by 5–39% compared to a well-established single integrating sphere setup. A small part of the bias can be explained by the bias of the single sphere. Yet the observed bias is quite significant if absolute accuracy of measurements is required. For relative measurements, e.g. for monitoring development of needle spectra over time, the double sphere system provides notable improvement. Furthermore, it might be possible to reduce the bias by building an optimized measurement setup that minimizes absorption losses in the sample port. Our study indicates that double spheres, after some technical improvement, may provide a new and fast way to collect extensive spectral libraries of tree species.

Accumulation of heavy metals in needles and bark of Pinus species

During the research, cumulative properties of conifer needles P. armandii, P. banksiana, P. mugo, P. nigra, P. sylvestris and P. wallichiana in reference to Cu, Ni, Mn, Fe, Zn and Cd were analysed, and the factors which have an impact on the chemical composition of the bark of those species were identified. During the study, the age of needles and the content of the examined components in soil was taken into consideration. The content of metals in the needles varied, depending on a species and the age of the coniferous needles. In most cases, a higher level of content of those metals was determined in 2 years old needles, except for Cu and Zn (P. banksiana) as well as Zn (P. nigra), in which case, higher concentration of metals in 1 year old needles was determined. The obtained results indicate that the heavy metals’ concentration in the samples of needles was relatively low, except for Ni (P. armandii, P. sylvestris, P. wallchiana) and Cd (P. armandii, P. banksiana), which showed higher levels. Among the examined elements, Mn was accumulated in the largest volume in the needles of P. banksiana, Fe and Cu in the needles of P. wallchiana, Ni in the needles of P. sylvestris, Zn in the needles of P. nigra and Cd in the needles of P. armandii. The bark samples represented a clearly acidic reaction, with pH levels from 3.7 (P. sylvestris) to 4.9 (P. armandii). The highest quantities of Mn, Fe, Cu and Cd were accumulated by the bark of P. armandii, Ni in the bark of P. sylvestris and Cu in the bark of P. mugo.

Interactions between leaf nitrogen status and longevity in relation to N cycling in three contrasting European forest canopies

Seasonal and spatial variations in foliar nitrogen (N) parameters were investigated in three European forests with different tree species, viz. beech (Fagus sylvatica L.), Douglas fir (Pseudotsuga menziesii, Mirb., Franco) and Scots pine (Pinus sylvestris L.) in Denmark, The Netherlands and Finland, respectively. This was done in order to obtain information about functional acclimation, tree internal N conservation and its relevance for both ecosystem internal N cycling and foliar N exchange with the atmosphere. Leaf N pools generally showed much higher seasonal variability in beech trees than in the coniferous canopies. The concentrations of N and chlorophyll in the beech leaves were synchronized with the seasonal course of solar radiation implying close physiological acclimation, which was not observed in the coniferous needles. During phases of intensive N metabolism in the beech leaves, the NH4+ concentration rose considerably. This was compensated for by a strong pH decrease resulting in relatively low Γ values (ratio between tissue NH4+ and H+). The Γ values in the coniferous were even smaller than in beech, indicating low probability of NH3 emissions from the foliage to the atmosphere as an N conserving mechanism. The reduction in foliage N content during senescence was interpreted as N re-translocation from the senescing leaves into the rest of the trees. The N re-translocation efficiency (ηr) ranged from 37 to 70% and decreased with the time necessary for full renewal of the canopy foliage. Comparison with literature data from in total 23 tree species showed a general tendency for ηr to on average be reduced by 8% per year the canopy stays longer, i.e. with each additional year it takes for canopy renewal. The boreal pine site returned the lowest amount of N via foliage litter to the soil, while the temperate Douglas fir stand which had the largest peak canopy N content and the lowestηr returned the highest amount of N to the soil. These results support the hypothesis that a high N status, e.g. as a consequence of chronically high atmospheric N inputs, increases ecosystem internal over tree-bulk-tissue internal N cycling in conifer stands. The two evergreen tree species investigated in the present study behaved very differently in all relevant parameters, i.e. needle longevity, Nc and ηr, showing that generalisations on tree internal vs. ecosystem internal N cycling cannot be made on the basis of the leaf habit alone.

Supercritical fluid extraction as a tool for isolation of monoterpenes from coniferous needles and walnut-tree leaves

Several monoterpenes, i.e., (+)-α-pinene, (−)-camphene, sabinene, (−)-β-pinene, myrcene, R-(+)-limonene, (−)-bornylacetate, (−)-trans-caryophyllene and a-humulene were identified and determined by gas chromatography-mass spectrometry (GC-MS) in needles of Pinaceae (Picea abies, P. omorika, P. pungens, P. Breweriana, Pinus nigra, P. mungo turra, P. black, P. sylvestris, Abies pinsapo, A. holophylla, A. Bronmuelleris, A. alba, Larix Kaempferi L. decidua) and tree-leaves of Juglandaceae (Juglans regia, J. nigra, J. sieboldiana var. Cordiformis) families. Supercritical fluid extraction (SFE) was found to be very useful for their isolation at optimised conditions (needles/leaves: pressure 20/30 MPa, temperature 80/130°C, time of extraction 60/60 min, modifier chloroform/chloroform). Their seasonal distribution, evaluation of differences in concentrations and relative amounts in different trees and their varieties grown in different localities were evaluated.