Red Pine Needles Research Articles

Evaluation and optimization of red pine needle-reinforced roller-compacted concrete by bioinspired algorithms

This paper discusses the improvement of roller compacted concrete by the addition of red pine needle (PN) fibers optimized by bioinspired techniques. The purpose was to determine a perfect set of mechanical characteristics, such as flexural, compressive, and splitting tensile strengths, by determining proper correlations between the water-cement ratio, superplasticizer, and fiber volume. Based on the data obtained with the help of experiments, it was shown that optimizing the PN fibers added to RCC with nature-inspired algorithms (particle swarm optimization, genetic algorithms, simulated annealing and artificial neural networks) yields positive results in terms of improving a number of characteristics, including flexural strength, fracture toughness, and durability. In addition, adopting PN fibers has certain environmental benefits. All methods under analysis showed good results, with the artificial neural network (ANN) being superior in terms of predicting the parameters of RCC. The discussed research confirms the effectiveness of such optimization methods for determining the best proportions for RCC using PN fibers. At the same time, future studies could further develop sustainable and mechanically strong RCC formulations.

Изменчивость биохимических признаков Pinus sylvestris (Pinaceae) при адаптации форм в условиях избыточного увлажнения

Conifers are characterized by a certain degree of individual variability in the content of stress metabolites, which can be caused by genotypic variations or divergence in the growth conditions of individual trees. The purpose of the study is to evaluate the variation of biochemical traits of Scots pine, which are different in the color of male strobilus, during adaptation to the conditions of constant excessive moisture in the soil of the northern taiga. The dynamics of metabolic parameters of Pinus sylvestris L. were investigated in shrubsphagnum pine stands on marshy upland soils at the mouth of the Northern Dvina River (northern taiga subzone). From July to November 2018, needle samples from shoots were collected from 10 pine trees of each of the male strobilus types, differentiated by color. The contents of photosynthetic pigments, anthocyanins, ascorbic acid, proline, water-soluble proteins, and pH were measured under laboratory conditions. The synthesis of chlorophyll in the needles in the current year of formation decreased in trees of both forms during the dry summer period. A favorable temperature in the autumn period could promote an extension of photosynthetic pigment accumulation, which might negatively affect tree preparation for overwintering. There were no significant differences between f. erythranthera Sanio and f. sulfuranthera Kozubow in the needle content of chlorophyll and carotenoids, anthocyanins, ascorbic acid, free proline, water-soluble proteins, or pH. The similarities in the adaptation of the trees to the constant excessive soil moisture in northern taiga conditions were revealed. The seasonal factor had a considerable impact on the dynamics of biochemical parameters. Ascorbic acid, proline, and anthocyanin were more actively accumulated in the needles throughout the summer due to the high air temperature, resulting in an increase in antioxidant activity and the development of protective mechanisms aimed at reducing oxidative stress. The increase in water-soluble protein content in needles from October to November is one of the cryoprotective mechanisms of the trees for the winter period. Individual differences in ascorbic acid and proline contents in yellow microspore-bearing pine needles at the establishment of minus temperatures in November were considerably higher than in red microspore-bearing pine needles. This is regarded as the norm of the reaction for different types of trees to the influence of negative temperatures. For citation: Tarkhanov S.N., Pinaevskaya E.A., Aganina Y.E., Pakhov A.S. Variability of Biochemical Properties During Adaptation of Pinus sylvestris (Pinaceae) Forms to Excessive Moisture Conditions. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 4, pp. 58–75. (In Russ.). https://doi.org/10.37482/0536-1036-2023-4-58-75

Identification and sequence determination of a new chrysovirus infecting the phytopathogenic fungus Dothistroma septosporum

A new double-stranded (ds) RNA mycovirus has been identified in isolate Ds752-1 of the phytopathogenic fungus Dothistroma septosporum, the causal agent of Dothistroma needle blight, also known as red band needle blight or pine needle blight. Dothistroma septosporum chrysovirus 1 (DsCV-1) is a new member of the genus Alphachrysovirus in the family Chrysoviridae. The DsCV-1 genome comprises four dsRNA elements designated 1, 2, 3, and 4 from largest to smallest. dsRNA1 encodes an RNA-dependent RNA polymerase (RdRP) that is most similar to the RdRP of Erysiphe necator associated chrysovirus 3. dsRNA2 potentially encodes two hypothetical proteins, one of which is small and has no homology to known proteins, and one of which is large with significant sequence similarity to the alphachryso-P3 of other alphachrysoviruses. dsRNA3 and dsRNA4 encode a coat protein (CP) and a putative cysteine protease, respectively. This is the first report of a mycovirus infecting the fungus D. septosporum, and DsCV-1 is one of three Chrysoviridae family members found to possess genomic dsRNAs potentially encoding more than one protein.

Composition of Essential Oils in Needles and Barks of Turkish Red Pine (Pinus brutia Ten.) Infested by Marchalina hellenica Genn.

The scale insect Marchalina hellenica Genn. plays a key role in pine honey production and is hosted mainly by Turkish red pine (Pinus brutia Ten.). The needles of Turkish red pine are rich in essential oils. Moreover, essential oils can affect the host selection of insects. The essential oils in the needles and barks of Marchalina hellenica-infested and non-infested Turkish red pine were obtained via water distillation and their composition was determined by GC-MS analyses. The composition of the essential oils was found to differ in the needles of non-infested Turkish red pine and in those of pine infested by Marchalina hellenica. The Mann-Whitney U test results showed that the β-caryophyllene level was higher in the needles of Turkish red pine infested by Marchalina hellenica, whereas the junipen level was higher in the essential oil of non-infested Turkish red pine bark. Pimaral and α-guaiene were detected only in the needles of infested trees, but were absent in the needles of non-infested trees. These components may be markers that can act on their own or as part of the whole in the host tree selection of Marchalina hellenica. In addition, the cis-verbenone component found in Turkish red pine bark might play a role in attracting Marchalina hellenica. This phenomenon should be further investigated through additional studies.

Investigation of mechanical properties of red pine needle fiber reinforced self-compacting ultra high performance concrete

With the increasing effects of global warming, the use of natural materials in engineering studies is increasing. In engineering construction, on the other hand, the use of natural fibers as concrete additives in order to reduce carbon emissions and protect the green environment is the focus of the studies. It is possible to increase ductility with the use of fiber in self-compacting ultra high performance concrete. The use of natural fibers provides an environmentally friendly approach. Therefore, in this study, the effect of red pine needles on the mechanical properties of self-compacting ultra high performance concrete was investigated. Pine needles were divided into 30, 40 and 50 mm length. The red pine needles were purified from organic matter with alkaline solution. It was added into the self-compacting ultra high performance concrete at the rates of 0.25%, 0.50%, 0.75% and 1.00% by volume. Slump-flow test, v-funnel test, compressive strength test, flexural strength test, freeze-thaw test, sulfate attack test were applied to examine the mechanical properties of the samples. In the sample with a length of 30 mm and a fiber content of 0.50%, the slump-flow test results decreased from 738 mm to 723 mm compared to the reference sample. According to the V-funnel test results, the closest results to the reference sample were obtained. The sample with a length of 30 mm and a fiber content of 0.50% provided a 15.6% increase in the 28-day compressive strength. On the other hand, the flexural strength increased from 8.60 MPa to 22.46 MPa according to the reference sample. In the sulfate attack test and freeze-thaw test, the closest results to the reference sample were obtained with the 30 mm length sample with 0.50% fiber content. With the results obtained, it was seen that the use of pine needles as a natural fiber in self-compacting concrete was appropriate.

Morphological Characteristics of Japanese Red Pine Needles from the Areas of the Fukushima NPP Accident

Morphological Characteristics of Japanese Red Pine Needles from the Areas of the Fukushima NPP Accident

홍고추 또는 솔잎 초임계 이산화탄소 추출물이 들기름의 산화안정성에 미치는 영향

The objective of this study was to determine the effects of supercritical carbon dioxide (SC-CO2) extracts from red pepper (RP) or pine needles (PN) on the physicochemical properties of perilla oil (PO). Subsequently, the physicochemical properties of the perilla oil containing SC-CO2 extract at 0.1% and PO without extract were compared. Oxidative stability was measured based on viscosity, acid value (AV), peroxide value (POV), antioxidant (2,2-diphenyl-1-picrahydrazyl) activity, p-anisidine value (p-AV), and fatty acid composition. All the samples were studied under medium temperature (65°C) accelerated oxidation conditions for 24 h. The viscosities of PO with PN extract and PO without extract significantly increased with increasing storage time, but that of PO added with RP extract was not significantly different (p<0.05). The oxidative stability properties, such as AV, POV, and p-AV, indicated that PO with RP or PN extracts exhibited superior oxidative stabilities than PO without extract. The antioxidant activities of all samples was significantly decreased with increasing the oxidation time (p<0.05). No significant differences in fatty acid composition between PO with and without extract were observed (p<0.05). Thus, the SC-CO2 extracts affect the lipid oxidative stability in perilla oil and may be used as natural antioxidant for food preservation.

Quantitative Changes of Flavonol Glycosides from Pine Needles by Cultivar, Harvest Season, and Thermal Process

Five flavonol glycosides including quercetin 3-O-β-D-glucoside (QG), kaempferol 3-O-β-D-glucoside (KG), quercetin 3-O-(6″-O-acetyl)-β-D-glucoside (QAG), kaempferol 3-O-(6″-O-acetyl)-β-D-glucoside (KAG), and quercetin 3-O-(3″-O-p-coumaroyl)-β-D-glucoside (QCG) were isolated and purified from red pine (Pinus densiflora Sieb. et Zucc.) nee-dles, and identified by nuclear magnetic resonance and mass spectrometer spectral analyses. In addition, the quantification of the five flavonol glycosides in pine needles was performed by high-performance liquid chromatography analysis according to cultivar, growing district, harvest season, and thermal processing. The red pine needles had higher amounts of the five flavonol glycosides than the black pine needles except for QCG. There were no large differences in flavonoid composition and content among pine needles grown in three different areas. Levels of the five flavonol glycosides in red pine needles harvested during Spring ranged from 6.13 to 27.03 mg/100 g dry weight. Levels of two flavonol glycosides, QG and KG, gradually decreased with increasing harvest time, whereas the acylated flavonol glycoside, QCG, a predominant flavo-noid in pine needles, increased gradually with increasing harvest time. Two acetyl flavonol glycosides, QAG and KAG, increased steadily through Spring to Autumn, and then decreased gradually by Winter. Meanwhile heat treatments, such as roasting and steaming, increased the five flavonol glycosides during heating for 3 min, but then slowly decreased these when heating for 10 min. Microwave processing increased to some extent the five flavonol glycosides when heating for 3 min, and remained unchanged during the 10 min heating. These results suggest that the pretreated red pine needles with enhanced flavonoid content may be useful as potential sources for nutraceuticals and cosmeceuticals.

Antihypertensive Effects of Dehydroabietic and 4-Epi-Trans-Communic Acid Isolated from Pinus densiflora.

Korean red pine needle (RPN) exhibits various biological and pharmacological activities. Among the various compounds of RPN, we isolated dehydroabietic and 4-epi-trans-communic acid. At first, we confirmed that two compounds inhibited angiotensin converting enzyme (ACE) and induced p-Akt in human umbilical vein endothelial cells (HUVEC). RPN extract powder significantly reduced systolic blood pressure in spontaneous hypertensive rats (SHRs) through the reduced expression of ACE and angiotensin type I receptors in the lungs of SHRs. The Lineweaver-Burk plots suggested that the two compounds were noncompetitive inhibitors of ACE. Using docking analysis, we found that two compounds showed the best returned pose at ACE active sites, and formed hydrogen and hydrophobic bonds with ACE residues. These results demonstrate that RPNs may be a source of compounds effective for preventing hypertension and may be useful in the development of antihypertensive drugs.

Multifaceted effects of chronic radiation exposure in Japanese red pines from Fukushima prefecture

Despite many studies carried out to date, the long-term effects of chronic exposure on plants and animals inhabiting the territories affected by the Fukushima Dai-Ichi NPP accident remain the subject of scientific discussions. Our investigations were performed on Japanese red pine, the native tree species that is widely spread in the radioactive contaminated areas. Earlier observations revealed the radiation-induced cancellation of the apical dominance in young trees of this species. To understand the mechanism of such transformation, we evaluated the morphometric parameters of needles, the frequency of cytogenetic abnormalities, and the concentrations of the major classes of phytohormones in several natural populations of young red pine trees growing under different exposure conditions in Fukushima prefecture. No significant relationships between the morphometric parameters of needles and dose rates at the experimental sites were revealed. The frequencies of aberrant cells in the needle's intercalary meristem and the frequencies of cancellation of the apical dominance in the young pine populations in the radioactive contaminated areas were significantly higher than in the reference population. However, only cytogenetic abnormalities increased with the dose rate. We have not found the relation between the frequency of cytogenetic abnormalities in needles and cancellation of the apical dominance in the individual trees. In this paper, for the first time, it is shown that chronic radiation exposure changes the concentration ratio of the major classes of phytohormones in the needles of Japanese red pine. Given the complete lack of information about the most important regulatory system of plants in chronically irradiated populations, this study fills a substantial gap in our knowledge. Finally, our findings indicated that the most probable causes of the cancellation of apical dominance observed in chronically exposed Japanese red pines are radiation damage to the apical meristems of the trees and changes in their phytohormonal balance.

Profiling Patterns of Volatile Organic Compounds in Intact, Senescent, and Litter Red Pine (Pinus densiflora Sieb. et Zucc.) Needles in Winter

This study was aimed to investigate the changes of chemical composition of the volatile organic compounds (VOCs) emitted from red pine needles in the process of needle abscission or senescence. The VOCs in intact, senescent, and litter red pine needle samples were analyzed by headspace-solid phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS). And then, multivariate statistical interpretation of the processed data sets was conducted to investigate similarities and dissimilarities of the needle samples. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to investigate the dataset structure and discrimination between samples, respectively. From the data preview, the levels of major components of VOCs from needles were not significantly different between needle samples. By PCA investigation, the data reduction according to classification based on the chlorophyll a / chlorophyll b (Ca/Cb) ratio were found to be ideal for differentiating intact, senescent, and litter needles. The following OPLS-DA taking Ca/Cb ratio as y-variables showed that needle samples were well grouped on score plot and had the significant discriminant compounds, respectively. Several compounds had significantly correlated with Ca/Cb ratio in a bivariate correlation analysis. Notably, the litter needles had a higher content of oxidized compounds than the intact needles. In summary, we found that chemical compositions of VOCs between intact, senescent, and litter needles are different each other and several compounds reflect characteristic of needle.

δ13C, δ15N, N concentration, C/N, and Ca/Al of Pinus densiflora foliage in Korean cities of different precipitation pH and atmospheric NO2 and SO2 levels

Forest decline due to atmospheric pollution is a consequence of long-term chronic exposure, and thus chemical proxies that are sensitive to the pollution are helpful in estimating the impact of atmospheric pollution on forest health. In this study, we explored changes in the isotopic and elemental compositions of needles of red pine (Pinus densiflora) with varying precipitation pH and concentrations of NO2 and SO2 across 18 cities to identify isotopic and chemical signatures that are sensitive to acid deposition. The cities had different intensity of traffic and industrial activities, and thus were expected to have varying levels of atmospheric pollution. The pine needles were analyzed for carbon (δ13C) and nitrogen (δ15N) isotope ratios, N concentrations, C-to-N ratio (C/N), and calcium-to-aluminum ratio (Ca/Al). Analysis of variance, simple linear correlation, and redundancy analysis were used to investigate the variations in foliar chemistry with atmospheric variables. Neither NO2 nor SO2 concentration was correlated with foliar δ13C, δ15N, N concentration, and C/N; whereas precipitation pH was correlated with the foliar parameters, suggesting that foliar chemistry is more sensitive to total acidifying materials than to individual pollutant. The foliar δ13C decreased with lowered precipitation pH, reflecting the increased 13C-depleted CO2 that was co-emitted with acidifying materials from fossil fuel combustion. Foliar δ15N decreased and foliar N concentration increased with lowered precipitation pH, indicating tree uptake of 15N-depleted N from acid deposition. Accordingly, the C/N ratio also decreased with lowered precipitation pH. However, there was no relationship between foliar Ca/Al and precipitation pH; rather. Our result suggests that δ13C, δ15N, N concentration, and C/N of pine needle samples are associated with the level of precipitation pH and thus pine needles could be used as bio-indicators of the impacts of total acidifying pollutants on forest.

Effects of Sho-ju-sen, a Japanese herbal medicine, on catechoamine secretion induced by acetylcholine in cultured bovine adrenal medullary cells

Sho-ju-sen is a Japanese herbal medicine which has been used as a nourishing tonic. It is composed of a water extract of Kumazasa leaves (Sasa kurinensis Makino et Sibata) and ethanol extracts of Japanese red pine needles (Pinus densiflora Sieb. Et Zucc) and ginseng roots (Panax ginseng C. A. Meyer). Previous studies showed that Sho-ju-sen has antidepressant and anxiolytic effects in mice (Phytother Res., 15: 142-147, 2001 and 18: 173-176, 2004). Here we report that the effects of Sho-ju-sen on catecholamine secretion in cultured bovine adrenal medullary cells. Adrenal medullary cells have provided a good material for the detailed analysis of a drug's actions on catecholamine secretion and have been used as a model of the sympathetic neurons. We found that Sho-ju-sen (0.5 - 1 %) and extract of Kumazasa leaves (0.5-1 %), but not ethanol extract of Japanese red pine needles or ginseng roots, concentration-dependently inhibited the secretion of catecholamines induced by acetylcholine, a physiological secretagogue and agonist of nicotinic acetylcholine receptors. In Xenopus oocytes expressing α3β4 nicotinic acetylcholine receptors, Sho-ju-sen (0.5 - 1 %) directly inhibited Na+ current evoked by acetylcholine. Sho-ju-sen (0.3 - 1 %) also inhibited catecholamine secretion induced by veratridine, an activator of voltage-dependent Na+ channels, but not by 56 mM K+ which depolarizes cell membranes. The present findings demonstrate that Sho-ju-sen inhibits acetylcholine- and veratridine-induced catecholamine secretion by suppression of nicotinic acetylcholine receptor-ion channels and voltage-dependent Na+ channels in adrenal medulla cells and probably sympathetic neurons, and also suggest that Sho-ju-sen has an anti-stress effect.

Seasonal Variation in Allelopathic Activity of Japanese Red Pine Needles

Seasonal Variation in Allelopathic Activity of Japanese Red Pine Needles

Size distribution of water-soluble components in particulate matter emitted from biomass burning

Size-resolved measurements of particulate matter (PM) emissions from 10 biomass materials (rice straw, soybean stem, green perilla stem, red pepper stem, pine needles, cherry leaves, cherry stem, maple leaves, gingko leaves and gingko stem) were conducted in a laboratory hood chamber environment using a 10-stage MOUDI. Samples were analyzed to determine the mass, water soluble organic carbon (WSOC), and water soluble inorganic species. This study examines how particle emissions and size distributions of chemical components vary with biomass materials. Mass fractions of water soluble organic mass (WSOM) (=1.6 × WSOC) and ionic species to the PM1.8 emissions varied significantly depending on the biomass type burned. The percent mass of WSOM in PM1.8 emissions ranged from 19.8% (green perilla stem) to 41.9% (red pepper stem) for agricultural crop residues, while the tree category accounted for 9.6% (gingko leaves) to 44.0% (gingko stem) of the PM1.8 emissions. Total ionic species contents in the PM1.8 mass ranged from 7.4% (rice straw) to 26.9% (green perilla stem) for the agricultural waste category, and 5.8% (maple leaves) to 23.5% (gingko stem) for the tree category. The ionic species fraction of the PM1.8 emission was dominated by K+, Cl−, and SO42−, while Ca2+ was important in the coarse mode particles (>3.1 μm). PM1.8 emissions of K+, Cl−, and SO42− were as high as 16.9%, 9.0%, and 5.8%, respectively, and were from the green perilla stem, red pepper stem, and gingko stem emissions.Normalized size distributions of mass, WSOC, K+, Cl−, SO42−, and oxalate in the biomass burning emissions showed a unimodal size distribution, peaking in the size ranges of 0.32–0.55 μm and 0.55–1.0 μm. Size-resolved PM mass fractions of WSOM, K+, Cl−, and SO42− showed fairly consistent distributions for each biomass type, with higher fractions in the ultrafine mode (<0.10 μm) and lower fractions in the accumulation mode of 0.32–1.0 μm. The size distributions of WSOC were strongly correlated (mostly R2 > 0.90) with those of K+ in the particle size range of <0.1 μm and 0.1–1.8 μm and the biomass types. Strong correlations between the concentrations of K+–Cl− and K+−SO42− were observed for the following size ranges; <0.1 μm, 0.1–1.0 μm, 1.0–1.8 μm, and 1.8–3.1 μm for most biomass burning emissions. Regression line slopes for K+/WSOC (i.e., mass of K+/mass of WSOC from biomass burning emissions) were not significantly changed for particle size and biomass type, but slopes for Cl−/K+ and SO42−/K+ varied significantly with the particle size (ultrafine, condensation, droplet, and coarse modes) and biomass type.

Contact and fumigant toxicity of Pinus densiflora needle hydrodistillate constituents and related compounds and efficacy of spray formulations containing the oil to Dermatophagoides farinae

The toxicity of red pine needle hydrodistillate (RPN-HD), 19 RPN-HD constituents and another 12 structurally related compounds and the control efficacy of four experimental spray formulations containing RPN-HD (0.5. 1, 2 and 3% sprays) to adult Dermatophagoides farinae were evaluated. RPN-HD (24 h LC50 , 68.33 µg cm(-2) ) was toxic to mites. Menthol was the most toxic compound (12.69 µg cm(-2) ), and the toxicity of this compound and benzyl benzoate did not differ significantly. High toxicity was also produced by α-terpineol, bornyl acetate, geranyl acetate, thymol, linalyl acetate, terpinyl acetate, citral, linalool and camphor (18.79-36.51 µg cm(-2) ). These compounds were more toxic than either deet or dibutyl phthalate. In vapour-phase mortality tests, these compounds were consistently more toxic in closed versus open containers, indicating that their mode of delivery was largely a result of vapour action. RPN-HD 3% experimental spray provided 95% mortality against adult D. farinae, whereas permethrin (cis:trans, 25:75) 2.5 g L(-1) spray treatment resulted in 0% mortality. In the light of global efforts to reduce the level of highly toxic synthetic acaricides in indoor environments, RPN-HD and the compounds described merit further study as potential biocides for the control of Dermatophagoides populations as fumigants with contact action.

Organ-specific-active allelopathic substance in red pine needles

An organ-specific-growth inhibitory substance was isolated from an aqueous methanol extract of red pine needles and determined by spectral data as 1-mono(16-hydroxyhexadecanoyl)glycerol. This substance inhibited root growth of cress (Lepidium sativum L.) and barnyard grass (Echinochloa crus-galli (L.) Beauv) seedlings at concentrations greater than 0.01 and 0.03 μM, respectively. The concentrations required for 50 % growth inhibition on roots of cress and barnyard grass were 0.16 and 3.4 μM, respectively. However, the inhibitory activity of the substance on shoots of cress and barnyard grass was very weak. The endogenous concentration of 1-mono(16-hydroxyhexadecanoyl)glycerol in the pine needles was 4.6 μmol kg−1. Two related compounds, 1-monohexadecanoylglycerol and 16-hydroxyhexadecanlic acid had no activity up to 1,000 μM on cress roots and shoots. The effectiveness of 1-mono(16-hydroxyhexadecanoyl)glycerol on root growth inhibition and the occurrence of 1-mono(16-hydroxyhexadecanoyl)glycerol in pine needles suggest the substance may play an important role in the allelopathy of red pine. Root-specific-growth-inhibition by the substance may be one of the strategies for red pine to compete with neighboring plants for nutrients and space because root growth of competitive plants may be very important for their whole plant development.

Impact of pine processionary moth (Thaumetopoea wilkinsoni Tams) on growth of Turkish red pine (Pinus brutia Ten.)

One of the most important damaging insects on Turkish red pine (Pinus brutia Ten.) forests in the coastal Mediterranean Region of Turkey is pine processionary moth (PPM), Thaumetopoea wilkinsoni Tams. The larvae of PPM feed on needles of Turkish red pine and on some other Mediterranean conifers such as cedar. This study covers the impact of defoliation caused by PPM on growth of red pine. Three test sites were taken on different plantations in the coastal Mediterranean region of Turkey, near Antalya city. The heights and diameters at breast height (dbh) of individual trees both in the control group and the treatment groups were measured. The trees defoliated over 40% in the test sites were considered as the treatments. The results indicated that, compared to the control, the losses in defoliated trees in terms of dbh increment were 55, 50 and 35% in the three test sites, respectively. The corresponding losses in the three test sites in terms of volume increment were 44, 37 and 17%, respectively. Test results also showed that effects of defoliation and site on both diameter and volume increment were statistically significant at 0.000 probability level.

Effects of an aqueous red pine (Pinus densiflora) needle extract on growth and physiological characteristics of soybean (Glycine max)

The effect of allelochemicals on growth, root nodule nitrogen fixation activity, and ion patterns of soybeans were investigated. We prepared 50 g/L (T50), 100 g/L (T100), and 200 g/L (T200) extract concentrations by soaking fresh red pine needles in a nutrient solution. Adding needles to the nutrient solution increased the content of total phenolic acids, osmolality, and total ions. The total phenolic content in the T50, T100, and T200 extracts were <TEX>$206{\pm}12.61$</TEX>, <TEX>$335{\pm}24.16$</TEX>, and <TEX>$603{\pm}12.30$</TEX> mg gallic acid equivalents, respectively. The <TEX>$K^+$</TEX>, <TEX>$Mg^{2+}$</TEX>, <TEX>$Ca^{2+}$</TEX>, and <TEX>$PO_4^{3-}$</TEX> content increased by adding needles to the nutrient solutions, whereas <TEX>$SO_4^{2-}$</TEX> content decreased. The growth inhibition of soybeans was proportional to the needle extract concentrations, and the T100 and T200 concentrations resulted in remarkable growth inhibition. On day 20 after treatment, dry weight and nitrogen fixation activity of the root nodules were reduced by the T100 and T200 treatments, whereas the T50 treatment was not difference from the control. After day 10, total ion content in all treatment groups was not different in comparison with the control. However, total ionic content in all treatment groups decreased significantly compared with that in the control after day 20. The lowest total ion value was found for the T200 concentration. The T200 treatment also resulted in significantly reduced <TEX>$SO_4^{2-}$</TEX> content. The amounts of <TEX>$Mg^{2+}$</TEX>, <TEX>$Ca^{2+}$</TEX>, and <TEX>$Mn^{2+}$</TEX> were higher than those of the control for the T50 treatment on day 10 and for T100 on day 20 after treatment. A significant increase in osmolality was observed in the T200 treatment on day 10 and in the T100 treatment on day 20. These results suggest that under severe allelochemical stress conditions, a remarkable reduction in nodule formation, nitrogen fixation activity, and ion uptake eventually resulted in a decrease in leaf production. Furthermore, increased <TEX>$K^+$</TEX>, <TEX>$Mg^{2+}$</TEX>, <TEX>$Ca^{2+}$</TEX>, <TEX>$Mn^{2+}$</TEX>, and osmolality in soybeans exposed to lower concentrations of allelochemicals than the critical stress level helped overcome the stress.

Allelopathy of red pine: isolation and identification of an allelopathic substance in red pine needles

Since red pine (Pinus densiflora Sieb. et Zucc.) often forms sparse forest floors where herbaceous plants do not grow well, allelopathy of red pine was investigated. A growth inhibitory substance was isolated from an aqueous methanol extract of red pine needles and determined by spectral data as abscisic acid-β-d-glucopyranosyl ester (ABA-GE). This substance inhibited root and shoot growth of cress and E. crus-galli seedlings at concentrations greater than 0.1 μM. The concentrations required for 50% growth inhibition on roots and shoots of cress were 0.23 and 0.61 μM, respectively, and those of E. crus-galli were 1.1 and 2.8 μM, respectively. The activity of ABA-β-d-glucosidase, which liberates free ABA from ABA-GE, in cress and E. crus-galli seedlings was 13–29 nmol mg−1 protein min−1. Endogenous concentration of ABA-GE in the pine needles was 4.1–21.5 μmol kg−1 and the concentration in soil water of the pine forest was 2.5 μM. The effectiveness of ABA-GE on growth inhibition and the occurrence of ABA-GE in pine needles and soil water suggest ABA-GE may play an important role in the allelopathy of red pine resulting in the formation of sparse forest floors.