Effects of 60 Hz 14 microT magnetic field on the apoptosis of testicular germ cell in mice

We recently reported that continuous exposure, for 8 weeks, of extremely low frequency (ELF) magnetic field (MF) of 0.1 or 0.5 mT might induce testicular germ cell apoptosis in BALB/c mice. In that report, the ELF MF exposure did not significantly affect the body weight or testicular weight, but significantly increased the incidence of testicular germ cell death. In the present study, we aimed to further characterize the effect of a 16-week continuous exposure to ELF MF of 14 or 200 microT on testicular germ cell apoptosis in mice. There were no significant effects of MF on body weight and testosterone levels in mice. In TUNEL staining (In situ terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick end labeling), germ cells showed a significantly higher apoptotic rate in exposed mice than in sham controls (P < 0.001). TUNEL-positive cells were mainly spermatogonia. In an electron microscopic study, degenerating spermatogonia showed condensation of nuclear chromatin similar to apoptosis. These results indicate that apoptosis may be induced in spermatogenic cells in mice by continuous exposure to 60 Hz MF of 14 microT.     

No effects of extremely low frequency magnetic fields found on cytotoxic activities and cytokine production of human peripheral blood mononuclear cells in vitro

Several epidemiologic studies have suggested an association between exposure to extremely low frequency (ELF) magnetic fields (MFs) and cancer in adults and children. A possible target of MFs is the immune system. The effects of the exposure to ELF MFs on the immunological functions of human peripheral blood mononuclear cells (PBMCs) obtained from healthy male volunteers were assessed by measuring the natural killer (NK) and lymphokine activated killer (LAK) activities and the production of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2), and interleukin-10 (IL-10). The PBMCs were exposed to three different MF: linearly polarized (vertical), circularly polarized, and elliptically polarized, at 50 and 60 Hz. Magnetic flux densities were set at 500, 100, 20, and 2 microT (rms) for vertical field and at 500 microT (rms) for the rotating fields. Using cytotoxicity assay and enzyme-linked immunosorbent assay (ELISA) for cytokine production, we could not find any effects of ELF MFs on the cytotoxic activities and the cytokines production of human PBMCs.     

Real-time measurement of cytosolic free calcium concentration in Jurkat cells during ELF magnetic field exposure and evaluation of the role of cell cycle

Extremely low frequency magnetic fields (ELF MF) have been reported to alter a number of cell signaling pathways, including those involved in proliferation, differentiation and apoptosis where cytosolic free calcium ([Ca(2+)](c)) plays an important role. To better understand the biological conditions under which ELF MF exposure might alter [Ca(2+)](c), we measured [Ca(2+)](c) by ratiometric fluorescence spectrophotometry during exposure to ELF MF in Jurkat E6.1 cells synchronized to different phases of the cell cycle. Suspensions of cells were exposed either to a near zero MF (Null) or a 60 Hz, 100 microT sinusoidal MF superimposed upon a collinear 78.1 microT static MF (AC + DC). An initial series of experiments indicated that the maximum increase in [Ca(2+)](c) above baseline after stimulation with anti-CD3 was significantly higher in samples exposed to AC + DC (n = 30) compared to Null (n = 30) with the largest difference in G2-M enriched samples. However, in a second study with G2-M enriched cells, samples treated with AC + DC (n = 17) were not statistically different from Null-treated samples (n = 27). Detailed analysis revealed that the dynamics in [Ca(2+)](c) before and after stimulation with anti-CD3 were dissimilar between Null samples from each study. From the results, we concluded (i) that the ELF MF increased [Ca(2+)](c) during an antibody-induced signaling event, (ii) that the ELF MF effect did not depend to a large degree on cell cycle, and (iii) that a field-related change in [Ca(2+)](c) signaling appeared to correlate with features in the [Ca(2+)](c) dynamics. Future work could evaluate [Ca(2+)](c) dynamics in relation to the phase of the cell cycle and inter-study variation, which may reveal factors important for the observation of real-time effects of ELF MF on [Ca(2+)](c).     

Influence of 50 Hz magnetic field on sex hormones and other fertility parameters of adult male rats

The effects of an extremely low frequency (ELF) magnetic field on the sex hormones and other fertility parameters of adult male Sprague-Dawley rats were investigated. Adult male rats were exposed to a 50 Hz sinusoidal magnetic field at approximately 25 microT (rms) for 18 consecutive weeks. There were no significant effects on the absolute body weight and the weight of the testes of the exposed rats. However, the weights of seminal vesicles and preputial glands were significantly reduced in the exposed male rats. Similarly, a significant reduction in sperm count was observed in the exposed group. Furthermore, there were no significant effects on the serum levels of male follicle stimulating hormone (FSH) during the 18 weeks of exposure period. On the other hand, there was a significant increase in the serum levels of male luteinizing hormone (LH) after 18 weeks of exposure (P < .005), while testosterone levels were significantly decreased only after 6 and 12 weeks of the exposure period. These results suggest that long term exposure to ELF could have adverse effects on mammalian fertility and reproduction.     

Absence of daytime 50 Hz, 100 microT(rms) magnetic field or bright light exposure effect on human performance and psychophysiological parameters

The purpose of this study was to reproduce and extend two earlier studies of the effects of human exposure to 50 Hz magnetic fields (MF). In a recent paper, we described results of two double-blind investigations performed to examine effects of 100 microT(rms) 50 Hz MF exposure on psychological parameters in the same group of healthy human volunteers. In each exposure session, at 1 week intervals, with sham, continuous, and intermittent (15 s ON/OFF cycles) MF conditions, mood ratings, performance measures, and electrophysiological measures were taken. In the first study, significant amplitude changes were observed in the event-related brain potentials (ERP) recorded during a dichotic listening task. In the second study, latency and reaction time (RT) slowing were seen on a visual discrimination task (P(300) paradigm). Although these results were little related to the number of parameters analysed, they indicate that low level 50 Hz MF might have a slight influence on ERP and RT under specific circumstances of sustained attention. Before concluding that moderately strong MF exposure can influence cognitive function, previous results should be replicated, using the same paradigms with another group of healthy volunteers. In the present study, 18 healthy subjects were exposed to three experimental sessions of 30 min each, given at 1 week intervals. The sessions consisted of continuous 100 microT(rms) 50 Hz MF exposure, sham condition, and bright light (5000 lux) exposure. The study was performed double-blind, with the exposure order counter-balanced. The data on mood, ERP, RT, and other performance measures did not show any differences among the sham exposure, light exposure, and MF exposure conditions. The results of this study do not support the hypothesis that extremely low frequency (ELF) MF exposure affects the brain's electrical activity or cognitive function at field strength (100 microT(rms)) similar to that found in very close proximity of some household and industrial electrical appliances and well in excess of the average MF strength (c. 0.1 microT) found in homes. The sensitivity of the experiment was possibly not sufficient to detect an effect at this relatively low MF, and larger sample sizes would be required in further studies.     

Studies of 50 Hz circularly polarized magnetic fields of up to 350 microT on reproduction and embryo-fetal development in rats: exposure during organogenesis or during preimplantation

Groups of mated female Sprague-Dawley rats were simultaneously exposed to 0 (sham exposed), 7, 70, or 350 microT (rms) circularly polarized 50 Hz magnetic fields (MF) for 22 h/day on gestational day 8-15, the period of rat fetal organogenesis (organogenesis study) or from day 0 to day 7 of gestation, the rat preimplantation period (preimplantation study). Developmental toxicity was assessed on gestational day 20. Identical experiments were repeated to confirm reproducibility of both studies. In both studies, statistically significant differences between exposed and sham exposed animals were observed in several measured parameters; however, these differences only appeared in one, but not both replicate experiments and generally at only an isolated exposure level. Because these differences were not reproducible and did not show a dose response relationship, they were not considered related to MF exposure. In the organogenesis study, lower kidney weights of dams were seen at 70 and 350 microT in Experiment 1. Lower dam liver weights and lower mean body weights of viable female and male fetuses were seen at 70 microT in Experiment 2. Otherwise, there were no differences in these parameters or in group means for fetal loss after implantation, number of viable fetuses, fetal body weight and sex ratio, incidences of external, visceral, and skeletal abnormalities or variations, or tissue abnormalities after histopathological examination. In the preimplantation study, dam health and indices for reproduction and embryo-fetal development, including pre or postimplantation loss, number and body weight of live fetuses, and sex ratio, external, skeletal abnormalities and variations, and skeletal ossification did not differ. Dam inorganic phosphorous concentration at 350 microT was elevated in one experiment and depressed in another. In one experiment, visceral abnormalities, primarily thymic remnant in neck and accessory liver lobe, were increased in the 7 microT group. Based on these results from two studies, we conclude that circularly polarized 50 Hz MF exposure of up to 350 microT during the fetal organogenesis or during the preimplantation period does not affect reproduction and embryo-fetal development in Sprague-Dawley rats.     

Development and evaluation of intermediate frequency magnetic field exposure system for studies of in vitro biological effects

We have developed an intermediate frequency (IF) magnetic field exposure system for in vitro studies. Since there are no previous studies on exposure to heating-frequency magnetic fields generated from an induction heating (IH) cook top, there is a strong need for such an exposure system and for biological studies of IF magnetic fields. This system mainly consists of a magnetic-field-generating coil housed inside an incubator, inside which cultured cells can be exposed to magnetic field. Two systems were prepared to allow the experiment to be conducted in a double-blind manner. The level of the generated magnetic field was set to 532 microT rms in the exposure space, 23 kHz, 80 times the value in the International Commission on Non-ionizing Radiation Protection (ICNIRP) guidelines, with a spatial field uniformity better than 3.8%. The waveforms were nearly sinusoidal. It was also confirmed that the parasitic electric field was 157 V/m rms and the induced electric field was 1.9 V/m rms. The temperature was maintained at 36.5 +/- 0.5 degrees C for 2 h. Furthermore, leaked magnetic flux density was 0.7 microT rms or lower at extremely low frequency (ELF) and IF in the stopped system when the other system was being operated, and the environmental magnetic flux density was 0.1 microT rms or lower at the center of the coils. As a result, it was confirmed that this system could be successfully used to evaluate the biological effects of exposure to IF magnetic fields.     

Changes in human EEG alpha activity following exposure to two different pulsed magnetic field sequences

The present study investigates the effects of a weak (+/-200 microT(pk)), pulsed, extremely low frequency magnetic field (ELF MF) upon the human electroencephalogram (EEG). We have previously determined that exposure to pulsed ELF MFs can affect the EEG, notably the alpha frequency (8-13 Hz) over the occipital-parietal region of the scalp. In the present study, subjects (n = 32) were exposed to two different pulsed MF sequences (1 and 2, used previously) that differed in presentation rate, in order to examine the effects upon the alpha frequency of the human EEG. Results suggest that compared to sham exposure, alpha activity was lowered over the occipital-parietal regions of the brain during exposure to Sequence 1, while alpha activity over the same regions was higher after Sequence 2 exposure. These effects occurred after approximately 5 min of pulsed MF exposure. The results also suggest that a previous exposure to the pulsed MF sequence determined subjects' responses in the present experiment. This study supports our previous observation of EEG changes after 5 min pulsed ELF MF exposure. The results of this study are also consistent with existing EEG experiments of ELF MF and mobile phone effects upon the brain.     

Developmental toxicity evaluation of ELF magnetic fields in Sprague-Dawley rats

To identify possible effects of horizontally polarized magnetic field (MF) exposure on maintenance of pregnancy and embryo-fetal development, an MF exposure system was designed and constructed and 96 time-mated female Sprague-Dawley (SD) rats (24/group) received continuous exposure to 60 Hz MF at field strengths of 0 (sham control) and 5, 83.3, or 500 microT (50, 833, or 5000 mG). Dams received MF or sham exposures for 22 h/day on gestational day 6-20. MF was monitored continuously throughout the study. There were no evidences of maternal toxicity or developmental toxicity in any MF exposed groups. Mean maternal body weight, organ weights, and hematological and serum biochemical parameters in groups exposed to MF did not differ from those in sham control. No exposure related differences in fetal deaths, fetal body weight, and placental weight were observed between MF exposed groups and sham control. External, visceral, and skeletal examination of fetuses demonstrated no significant differences in the incidence of fetal malformations between MF exposed and sham control groups. In conclusion, exposure of pregnant rats to 60 Hz at MF strengths up to 500 microT during gestation day 6-20 did not produce any biologically significant effect in either dams or fetuses.     

Factors confounding cytosolic calcium measurements in Jurkat E6.1 cells during exposure to ELF magnetic fields

Reported changes in the cytosolic calcium concentration ([Ca2+](c)) as a result of exposure to extremely low frequency (ELF) magnetic fields (MF) have been equivocal. In this study, we examine the possibility that some of these differences are attributable to variability associated with the cell cycle, pH of the suspension medium, and response to a calcium agonist. We used a custom designed spectrofluorimeter to measure [Ca2+](c) in Indo 1-AM loaded Jurkat E6.1 cells suspended in conditioned RPMI 1640 medium containing 10% fetal bovine serum. Four exposures were examined: zero static MF (Null), 60 Hz 100 microT(peak) sinusoidal MF (AC), 78 microT static MF (DC), and the combination of the 60 Hz and the 78 microT static MF (AD + DC). A significant decrease in normalized [Ca2+](c) values between 375-495 s for the DC and AC + DC groups was found in comparison to the Null group. However, statistical analysis indicated that cell cycle and quality of the alpha-CD3 monoclonal antibody response were significant covariates, while pH was not a significant covariate. When the effect of these covariates was taken into account, all exposure groups were significantly different from the control. Our results suggest that ELF MF effects may not be seen unless correction is made for biological variability of each cell preparation with respect to cell cycle and [Ca2+](c) response to antigen stimulation.     

Synergic effect of retinoic acid and extremely low frequency magnetic field exposure on human neuroblastoma cell line BE(2)C

The aim of the present study was to assess whether exposure to a sinusoidal extremely low frequency magnetic field (ELF‐MF; 50 Hz, 1 mT) can affect proliferation and differentiation in the human neuroblastoma cell line BE(2)C, which is representative of high risk neuroblastomas. Cells were subjected to ELF‐MF exposure in the presence or absence of a neuronal differentiating agent (all‐trans‐retinoic acid, ATRA) for 24–72 h. In each experiment, ELF‐MF‐exposed samples were compared to sham‐exposed samples. Cells exposed to ELF‐MF combined with retinoic treatment showed a decreased cellular proliferation and an increased proportion of G₀/G₁ phase cells compared to cells exposed to either treatment alone. Moreover, ELF‐MF‐ and ATRA‐treated cells showed more differentiated morphological traits (a higher neurite number/cell, an increased neurite length), together with a significant increase of mRNA levels of p21^WAF1/CIP1 and cdk5 genes, both involved in neuronal differentiation. In addition, the expression of cyp19 gene, which is involved both in neuronal differentiation and stress response, was evaluated; cyp19 gene expression was enhanced by ATRA treatment and significantly enhanced further by ELF‐MF exposure combined with ATRA. In conclusion, our data suggest that ELF‐MF exposure can strengthen ATRA effects on neuroblastoma cells. Bioelectromagnetics 31:425–433, 2010. © 2010 Wiley‐Liss, Inc.     

Long-term exposure of male and female mice to 50 Hz magnetic field: effects on fertility

The effect of an extremely low frequency (ELF) magnetic field on the fertility of adult male and female Swiss mice was investigated. Adult male and female mice were exposed to a 50 Hz sinusoidal magnetic field at approximately 25 microT (rms) for 90 days before they were mated with unexposed counterparts. There were no exposure related effects on the fertility of male or female mice. The number of implantation sites, viable fetuses, and the total number of resorptions were not significantly affected in females impregnated by males exposed to the 50 Hz magnetic field as compared with the control group. The number of implantation sites, viable fetuses and the total number of resorptions in exposed females were also not statistically different from the control group. There were no significant effects on the weights of the testes, seminal vesicles, preputial gland or body weights of males exposed to 50 Hz magnetic field. Furthermore, body and uterine weights were not affected in females exposed to 50 Hz field; however, ovarian weight was significantly increased in females exposed to the same field. These results suggest that exposure of male and female mice to low frequency magnetic field had no adverse effects on fertility and reproduction in mice.     

Lack of adverse effects in pregnant/lactating female rats and their offspring following pre- and postnatal exposure to ELF magnetic fields

We have recently reported that exposure of pregnant rats to 60 Hz at field strengths up to 0.5 mT during the entire period of pregnancy did not induce any biologically significant effects on both pregnant dams and embryo-fetal development. The present study was carried out to investigate the potential effects of gestational and lactational MF exposure on pregnancy, delivery, and lactation of dams and growth, behavior, and mating performance of their offspring in rats. Timed-pregnant female Sprague-Dawley (SD) rats (24/group) received continuous exposure to 60 Hz magnetic field (MF) at field strengths of 0 (sham control), 5 microT, 83.3 microT, or 0.5 mT. Dams received MF or sham exposures for 21 h/day from gestational day 6 through lactational day 21. Experimentally generated MF was monitored continuously throughout the study. No exposure-related changes in clinical signs, body weight, food consumption, pregnancy length, and necropsy findings were observed in dams. Parameters of growth, behavior, and reproductive performance of offspring showed no changes related to MF exposure. There were no adverse effects on embryo-fetal development of F2 offspring from dams exposed to MF. In conclusion, exposure of pregnant SD rats to 60 Hz at field strengths up to 0.5 mT from gestational day 6 to lactational day 21 did not produce biologically significant effects in dams, F1 offspring, or F2 fetuses.     

Investigation of protein expression in magnetic field-treated human glioma cells

We previously reported phenotypic changes in human breast cancer cells following low-level magnetic field (MF) exposure. Here proteomic methods were used to investigate the biochemical effect of MF exposure in SF767 human glioma cells. Protein alterations were studied after exposure to 1.2 microTesla (microT) MF [12 milliGauss (mG), 60 Hertz (Hz)] +/- epidermal growth factor (EGF). SF767 cells were exposed for 3 h to sham conditions (<0.2 microT ambient field strength) or 1.2 microT MF (+/-EGF; 10 ng/ml). Solubilized protein fractions (sham; 1.2 microT; sham + EGF; 1.2 microT + EGF) were loaded for electrophoresis by 2D-PAGE and stained using a colloidal Coomassie blue technique to resolve and characterize the proteins. Protein patterns were compared across groups via Student's t-test using PDQUEST software. Cell profiles revealed significant alterations in the spot density of a subset of treated cells. Automated spot excision and processing was performed prior to peptide mass fingerprinting proteins of interest. Fifty-seven proteins from the detectable pool were identified and/or found to differ significantly across treatment groups. The mean abundance of 10 identified proteins was altered following 1.2 microT exposure. In the presence of EGF six proteins were altered after low magnetic field treatment by increasing (4) or decreasing (2) in abundance. The results suggest that the analysis of differentially expressed proteins in SF767 cells may be useful as biomarkers for biological changes caused by exposure to magnetic fields.     

Effects of Extremely Low Frequency Magnetic Fields on Blood Coagulation in Mice: An Initial Study

OF1 mice were chronically exposed to a 50‐Hz sinusoidal East–West magnetic field 15 µT (rms), in order to evaluate the blood coagulation variations related to the effect of this nonionizing radiation. Mating and pregnancy of ancestors (first generation), and birth, lactation, and development of second‐generation female mice until adulthood took place in the experimental field. A global blood coagulation study of both control and exposed 14‐ to 15‐week‐old and 50‐ to 52‐week‐old, second‐generation females was carried out. Plasma calcium content was determined by atomic absorption spectrophotometry. Different steps of blood coagulation were studied by thromboelastography (TEG) in whole blood (WB), platelet‐rich plasma (PRP), and platelet‐poor plasma (PPP). A significant decrease (approximately 34.5%) of calcium concentration was detected with aging; however, no change was induced by medium‐term or long‐term exposure to extremely low frequency magnetic field (ELF‐MF). Medium‐term exposure could not be related to noticeable changes in global coagulation. However, a great deterioration of fibrin clot formation in mature exposed female mice was detected as a result of the long‐term exposure that was strengthened by aging. These deficiencies seemed to be compensated by the discrete, although statistically not significant, decrease of platelet counts and the significant decrease of blood cells' mean corpuscular volume associated to ELF‐MF exposure of 50‐Hz, 15 µT. Consequently, whole blood TEG values of mature exposed female mice were similar to those from the young control group. In view of the obtained results, further studies on variations associated with ELF‐MF exposure in different coagulation parameters will be necessary.     

Human electrophysiological and cognitive effects of exposure to ELF magnetic and ELF modulated RF and microwave fields: a review of recent studies

The investigation of weak (<500 microT), extremely low frequency (ELF, 0-300 Hz) magnetic field (MF) exposure upon human cognition and electrophysiology has yielded incomplete and contradictory evidence that MFs interact with human biology. This may be due to the small number of studies undertaken examining ELF MF effects upon the human electroencephalogram (EEG), and the associated analysis of evoked related potentials (ERPs). Relatively few studies have examined how MF exposure may affect cognitive and perceptual processing in human subjects. The introduction of this review considers some of the recent studies of ELF MF exposure upon the EEG, ERPs and cognitive and perceptual tasks. We also consider some of the confounding factors within current human MF studies and suggest some new strategies for further experimentation.     

Extremely low frequency weak magnetic fields enhance resistance of NN tobacco plants to tobacco mosaic virus and elicit stress-related biochemical activities

Increasing evidence has accumulated concerning the biological effects of extremely low frequency magnetic fields (ELF-MFs) in different plant models. In the present study, effects of ELF-MFs in tobacco plants reacting to tobacco mosaic virus (TMV) with a hypersensitive response (HR) were evaluated. Plants were exposed for 8 or 24 h (either before or after TMV inoculation) to a static MF, at either -17 or 13 microT, combined with a 10 Hz sinusoidal MF with different intensities (25.6 or 28.9 microT). The working variables were the area and number of hypersensitive lesions in leaves. Following ELF-MFs exposure, an increased resistance was detected, particularly after an 8-h treatment, as shown by the decrease in lesion area and number. Moreover, two enzyme activities involved in resistance mechanisms were analyzed: ornithine decarboxylase (ODC) and phenylalanine ammonia-lyase (PAL). Uninoculated leaves previously exposed to ELF-MFs in general showed a significant increase relative to controls in ODC and PAL activities, in particular for 13 microT static MF plus 28.9 microT, 10 Hz sinusoidal MF (24 h) treatment. In conclusion, ELF-MFs seem to influence the HR of tobacco to TMV, as shown by the increased resistance and changes in ODC and PAL activities, indicating the reliability of the present plant model in the study of bioelectromagnetic interactions.     

Chronic exposure to ELF magnetic fields during night sleep with electric sheet: effects on diurnal melatonin rhythms in men

The possible effects of repeated night-time exposure to an extremely low frequency magnetic field (ELF-MF) on melatonin were investigated in nine healthy male subjects aged 23-37 yr. The 16-week experiment consisted of 3 weeks of pre-exposure, 11 weeks of night-time exposure to MF generated from a nonheated electric sheet (ES), and 2 weeks of post-exposure recovery observation. The average MF intensity (rms, mainly 50 Hz AC) on the surface of the sheet was 0.7 microT at the head, 8.3 microT at the waist, and 3.5 microT at the feet of the subject. For each of the urine samples collected 5 times a day on scheduled sampling days, the urinary excretion rate (ng/h) of melatonin was determined, and 24 h rhythms were extracted for each subject and each experimental period (pre-exposure, first half and latter half exposure, and post-exposure periods) by the method of complex cosine curve fitting. Although estimates of the peak height, acrophase, and total daily amount of melatonin were characterized by significant variations among individual subjects, they did not reveal any statistically significant difference between exposure periods and nonexposure periods. Thus, the present study indicates that any profound effect of the MF originating from an ES on nocturnal melatonin production and its circadian rhythm is unlikely.     

高CO2浓度下4种豆科乔木种子萌发和幼苗生长

 本文研究了高CO2浓度(550×10-6±50×10-6)对4种豆科乔木的种子萌发和幼苗生长的影响,结果如下：(1)高CO2浓度能使光叶红豆种子萌发率提高12％,对其它种的萌发没有明显影响。(2)高CO2环境能增加4种幼苗根瘤数量,提高根瘤的固氮活性和根瘤中可溶性糖的含量。(3)在高CO2环境下生长的幼苗叶片净光合速率比对照CO2环境(约350×10-6)下生长的幼苗提高66.7％～105.9％。在高CO2浓度和对照CO2浓度下生长的幼苗,移至相同C02浓度下测定时,光合速率无明显的差异。高CO2环境下生长并测定的幼苗叶片暗呼吸速率和对照CO2浓度下生长并测定的幼苗的测值差异不大,前者较后者低5.58％～l0.55％。(4)在高CO2环境下生长的4种幼苗干物质比对照的增加29.79％～50.30％,根系增加量较大,根冠比略上升。幼苗的相对生长速率和单位叶率上升,而叶面积比率下降。(5)幼苗对高CO2环境的反应和种的生态特性有关。喜光的大叶合欢幼苗对高CO2环境的反应较大,喜光而具一定耐荫性的猴耳环幼苗次之,而耐荫的光叶红豆和茸荚红豆幼苗则较小。