In vitro and ex vivo biofilms of dermatophytes: a new panorama for the study of antifungal drugs

Abstract

This study describes an ex vivo model that creates an environment for dermatophyte biofilm growth, with features that resemble those of in vivo conditions, designing a new panorama for the study of antifungal susceptibility. Regarding planktonic susceptibility, MIC ranges were 0.125-1?µg ml^?1 for griseofulvin and 0.000097-0.25?µg ml^?1 for itraconazole and terbinafine. sMIC50 ranges were 2->512?µg ml^?1 for griseofulvin and 0.25->64?µg ml^?1 for itraconazole and terbinafine. CLSM images demonstrated a reduction in the amount of cells within the biofilm, but hyphae and conidia were still observed and biofilm biomass was maintained. SEM analysis demonstrated a retraction in the biofilm matrix, but fungal structures and water channels were preserved. These results show that ex vivo biofilms are more tolerant to antifungal drugs than in vitro biofilms, suggesting that environmental and nutritional conditions created by this ex vivo model favor biofilm growth and robustness, and hence drug tolerance.     

An Evaluation of Risk Factors in Pregnant Women with <Emphasis Type="Italic">Candida</Emphasis> Vaginitis and the Diagnostic Value of Simultaneous Vaginal and Rectal Sampling

In this study, we investigated the epidemiological characteristics of VVC among pregnant women. We conducted a prospective survey among 372 pregnant women to investigate the prevalence, clinical forms, etiological agents, and predisposing factors of VVC. In addition, we determined the relationship between vaginal and rectal flora by simultaneously obtaining one high vaginal swab and one rectal swab from each patient using sterile cotton-tipped swabs. Furthermore, we compared the recovery and identification performances of chromID Candida agar to Sabouraud dextrose agar with gentamicin and chloramphenicol. Clinically and mycologically confirmed cases of VVC were detected in 139 (37.4%) and vaginal colonization described in 42 (11.3%) of 372 pregnant women. Rectal cultures were also positive in 98 of the 139 (70.5%) VVC cases. Candida albicans and C. glabrata were identified in vaginal samples in 58.0 versus 19.0% and from rectal samples in 49.0 versus 13.5%, respectively. Increases in gestational week and gravidae were identified to be statistically significant in patients with acute VVC (AVVC) and symptomatic recurrent VVC (RVVC), and asymptomatic RVVC (P = 0.04 and P = 0.03, respectively). In the laboratory diagnosis of VVC, specifically tailored chromogenic media are reliable tools for both the recovery and rapid identification of common Candida spp., particularly C. albicans, as well as for the detection of polyfungal populations in vaginal samples (P > 0.05). In addition, rectal colonization is a common finding in cases of AVVC and symptomatic-RVVC cases and corresponds well with the presence of the same yeast species in the vagina.     

The liquid Kangfuxin (KFX) has efficient antifungal activity and can be used in the treatment of vulvovaginal candidiasis in mice

Vulvovaginal candidiasis (VVC) is an infectious disease caused mainly by Candida albicans. Kangfuxin (KFX) is a traditional Chinese medicine preparation made from Periplaneta americana extracts, which promotes wound healing and enhances body immunity and also acts as an antifungal agent. Here, we evaluated the effect of KFX in the treatment of VVC in vitro and in vivo. The minimum inhibitory concentration (MIC₅₀) of KFX against C. albicans ranged from 7·65 to 20·57%. In addition, KFX was more efficient than fluconazole (FLC) in inhibiting the drug-resistant C. albicans, and the effect was more intense after 8 h. The KFX treatment also exhibited good activity in vivo. It restored the body weight and reduced the vulvovaginal symptoms in mice induced with VVC. It downregulated the expression of the hyphae-related gene, HWP1, thus inhibiting the growth and development of C. albicans hyphae. It also increased the number of neutrophils and promoted the secretion of interleukin-17A (IL-17A); however, the levels of interleukin-8 (IL-8) and interleukin-1β (IL-1β) decreased in mice with VVC. We deduce that KFX effectively treats vaginal candidiasis in two ways: by inhibiting the growth and development of mycelia to reduce colonization of C. albicans and by promoting the secretion and release of IL-17A and neutrophils in high numbers to fight C. albicans infection. This study provides a theoretical basis for the use of KFX for the clinical treatment of VVC.     

A New Model of Vaginal Infection by <Emphasis Type="Italic">Candida albicans</Emphasis> in Rats

Vulvovaginal candidiasis (VVC) is regarded as an important public health issue, and several aspects of its pathogenesis are not yet sufficiently clear. Experimental in vivo models of vaginal infection with Candida albicans have been extremely useful in the identification of factors concerning hormonal influences on the infection, the virulence of the yeasts, the susceptibility, and the treatment of the infection. The development of easily manageable, reproducible, and economically viable animal models of VVC is highly important. We describe a simple experimental model of VVC in rats, using a pharmaceutical brand of estradiol hexa-hydrobenzoate for human treatment. All the steps of this model were standardized; and after the experiments, the rats were euthanized for further examination of their tissues by scanning and transmission electron microscopy. Standardized features included the use of non-ovariectomized rats, sterile distilled water as the hormone vehicle, estradiol hexa-hydrobenzoate administered at 0.20 mg/week/rat fractionated three times/week, and a yeast suspension of 5 × 10⁸ yeasts/ml in a single vaginal administration 1 week after hormone induction. In this way, 100% of the rats were in pseudo-estrus and developed and maintained the infection until the third week of the experiment. Electron microscopy observation of the vagina of the rats confirmed the presence of both pseudo-estrus and vaginal infection. The standardized experimental model proved inexpensive, reproducible, and easily feasible for the induction of vaginal infection with C. albicans and may help to clarify important aspects of the pathogenesis and treatment of VVC.     

Protocols for Vaginal Inoculation and Sample Collection in the Experimental Mouse Model of Candida vaginitis

Vulvovaginal candidiasis (VVC), caused by Candida species, is a fungal infection of the lower female genital tract that affects approximately 75% of otherwise healthy women during their reproductive years^18,32-34. Predisposing factors include antibiotic usage, uncontrolled diabetes and disturbance in reproductive hormone levels due to pregnancy, oral contraceptives or hormone replacement therapies^33,34. Recurrent VVC (RVVC), defined as three or more episodes per year, affects a separate 5 to 8% of women with no predisposing factors³³.An experimental mouse model of VVC has been established and used to study the pathogenesis and mucosal host response to Candida^{3,4,11,16,17,19,21,25,37}. This model has also been employed to test potential antifungal therapies in vivo^13,24. The model requires that the animals be maintained in a state of pseudoestrus for optimal Candida colonization/infection^6,14,23. Under such conditions, inoculated animals will have detectable vaginal fungal burden for weeks to months. Past studies show an extremely high parallel between the animal model and human infection relative to immunological and physiological properties^3,16,21. Differences, however, include a lack of Candida as normal vaginal flora and a neutral vaginal pH in the mice.Here, we demonstrate a series of key methods in the mouse vaginitis model that include vaginal inoculation, rapid collection of vaginal specimens, assessment of vaginal fungal burden, and tissue preparations for cellular extraction/isolation. This is followed by representative results for constituents of vaginal lavage fluid, fungal burden, and draining lymph node leukocyte yields. With the use of anesthetics, lavage samples can be collected at multiple time points on the same mice for longitudinal evaluation of infection/colonization. Furthermore, this model requires no immunosuppressive agents to initiate infection, allowing immunological studies under defined host conditions. Finally, the model and each technique introduced here could potentially give rise to use of the methodologies to examine other infectious diseases of the lower female genital tract (bacterial, parasitic, viral) and respective local or systemic host defenses.     

Diverse Vaginal Microbiomes in Reproductive-Age Women with Vulvovaginal Candidiasis

Vulvovaginal candidiasis (VVC) is one of the most prevalent vaginal infectious diseases, and there are controversial reports regarding the diversity of the associated vaginal microbiota. We determined the vaginal microbial community in patients with VVC, bacterial vaginosis (BV), and mixed infection of VVC and BV using Illumina sequencing of 16S rRNA tags. Our results revealed for the first time the highly variable patterns of the vaginal microbiome from VVC patients. In general, the alpha-diversity results of species richness and evenness showed the following order: normal control < VVC only < mixed BV and VVC infection < BV only. The beta-diversity comparison of community structures also showed an intermediate composition of VVC between the control and BV samples. A detailed comparison showed that, although the control and BV communities had typical patterns, the vaginal microbiota of VVC is complex. The mixed BV and VVC infection group showed a unique pattern, with a relatively higher abundance of Lactobacillus than the BV group and higher abundance of Prevotella, Gardnerella, and Atopobium than the normal control. In contrast, the VVC-only group could not be described by any single profile, ranging from a community structure similar to the normal control (predominated with Lactobacillus) to BV-like community structures (abundant with Gardnerella and Atopobium). Treatment of VVC resulted in inconsistent changes of the vaginal microbiota, with four BV/VVC samples recovering to a higher Lactobacillus level, whereas many VVC-only patients did not. These results will be useful for future studies on the role of vaginal microbiota in VVC and related infectious diseases.     

Effect of pepstatin A on the virulence factors of Candida albicans strains isolated from vaginal environment of patients in three different clinical conditions

The aspartate proteinase inhibitor pepstatin A was used to study a possible correlation among proteinase activity and other virulence factors of Candida albicans strains isolated from the vaginal environment of patients in three different clinical conditions: asympthomatic, vulvovaginal candidiasis (VVC) and recurrent vulvovaginal candidiasis (RVVC). The addition of 1.0 μM pepstatin A did not have any significant effect on hyphae formation, biofilm production and in the cell surface hydrofobicity of isolates in the three different clinical conditions. However, pepstatin A reduced the adherence of C. albicans to vaginal mucosa epithelial cells (53.1, 48.7 and 59.9%, respectively to isolates from asymptomatic, VVC and RVVC patients). This result suggests that the secreted aspartate proteinases (Saps) of this fungal pathogen may have auxiliary roles in cellular adhesion.     

Modeling of growth kinetics for an isolated marine bacterium,Oceanimonas sp. BPMS22 during the production of a trypsin inhibitor

Abstract

Protease inhibitors significantly control physiologically relevant protease activities. Protease inhibitors from marine microbial sources are unique due to their rough living environmental conditions. In the present study, a protein protease inhibitor (PI) was produced from marine Oceanimonas sp. BPMS22. Seven different media were screened for the growth of the bacterium and production of PI. Different carbon and nitrogen sources were screened and optimized for the specific protease inhibitor activity. Three different growth models were checked for the best fit of the bacterial growth. A modified Gompertz model was selected as the best model for the growth of Oceanimonas sp. BPMS22 with the maximum specific growth rate of 0.165?hr^?1 and doubling time of 4.2?hr. The production of PI takes place during the non-growing phase of the bacterial growth. A kinetic model for the production of PI during non-growing phase was used for studying various process parameters. From the model, the maximum trypsin inhibitor formation rate of 0.3802?IU per mg of biomass per hour was observed at 49.91?hr.     

Physiological responses,tolerance efficiency,and phytoextraction potential of Hylotelephium spectabile (Boreau) H. Ohba under Cd stress in hydroponic condition

Abstract

A sand hydroponic experiment with different concentrations of 0, 5, 10, 20, 40?mg L^?1 Cd was used to study the growth and physiological response of Hylotelephium spectabile (Boreau) H. Ohba. and its phytoextraction potential for Cd. The results showed that total plant biomass under 5?mg L^?1 Cd treatment was slightly affected. The content of malondialdehyde (MDA) in leaf exposed to Cd was higher, and the POD and CAT activity exhibited a positive response to the low level of Cd addition (5?mg·L^?1). The photosynthesis pigments were slightly inhibited, and the ultrastructure of chloroplast remained intact after treatment with 10?mg L^?1 Cd. The maximum leaf Cd content (603?mg·kg^?1) was found in 5?mg L^?1 Cd treatment, then decreased with the Cd level increased. The maximum Cd content in the shoots far exceeds the threshold level (100?mg kg^?1) for a Cd-hyperaccumulator plant with the value of translocation factor (TF_shoot/root) for Cd reaching up to 5.62. In conclusion, H. spectabile showed normal growth and physiological response and high shoot Cd accumulation under 5?mg L^?1 Cd stress, which made it to be a good candidate for phytoextraction of low-level Cd polluted environment.     

Vulvovaginal candidiasis is associated with the production of germ tubes by <Emphasis Type="Italic">Candida albicans</Emphasis>

Twenty Candida albicans strains isolated from women attended at the Teaching and Research in the Laboratory of Teaching and Research in Clinical Analysis of the State University of Maringa, Paraná, Brazil, have been analyzed. Yeasts were identified by classical methods and patients subdivided into asymptomatic, vulvovaginal candidiasis(VVC) and recurrent vulvovaginal candidiasis (RVVC) groups. Yeasts were incubated in RPMI + fetal calf serum to analyze germ tubes every two hours, up to 10 h. In vitro sensitivity to fluconazole, itraconazole, ketoconazole, amphotericin B and nystatin was analyzed according to NCCLS-M27-A microdilution assay. Yeast isolated from symptomatic women produced significantly more germ tubes than asymptomatic women (P < 0.05). However, no significant difference between yeasts from VVC and RVVC occurred (P > 0.05). Variation between MIC₅₀ and MIC₉₀ of tested antifungal agents was slight among isolated yeasts, while no resistant yeasts were detected. Nevertheless, VVC yeasts were more DDS (reduced dose-dependent susceptibility) for nystatin and RVVC were more DDS for ketoconazole. Results suggest that colonization by yeast in the vagina and lack of symptoms may be partially explained by the yeast’s sparse capacity to form germ tubes, On the other hand, RVVC was not associated with antimicrobial resistance. DDS high frequency for nystatin and ketoconazole indicates that identification, and susceptibility of antifungals tests are important to management of VVC.     

The Role of 17β-Estrogen in Candida albicans Adhesion on Human Vaginal Epithelial Cells via FAK Phosphorylation

Purposes

To investigate the role of 17β-estrogen in Candida albicans (C. albicans) adhesion on human vaginal epithelial cells in vulvovaginal candidiasis (VVC).

Methods

The vaginal epithelial cell line, VK2/E6E7, was used to study the estrogen-induced molecular events between C. albicans and cells. An adhesion study was performed to evaluate the involvement of the estrogen-dependent focal adhesion kinase (FAK) activation in cell adhesion. The phosphorylation status of FAK and estrogen receptor α (ERα) upon estrogen challenge was assessed by western blotting. Specific inhibitors for ERα were used to validate the involvement of ERα–FAK signaling cascade.

Results

A transient activation of ERα and FAK was observed following the stimulation with 1000 nM estrogen for 48 h, as well as the increased average number of C. albicans adhering to each vaginal epithelial cell. Estrogen-induced activation of ERa and FAK was inhibited by the specific inhibitor of ERα, especially when the inhibitor reached a 10 μM concentration and allowed to act for 12 h. Simultaneously, a decrease in the number of adherent C. albicans was observed. However, this inhibitory effect diminished as the concentration of estrogen increased.

Conclusion

FAK and ERα signaling cascades were involved in the early interaction between the vaginal epithelial cells and C. albicans, which appeared to be linked with the enhanced cell adhesion leading to VVC and promoted by a certain concentration of estrogen.

     

Comparing the Recurrence of Vulvovaginal Candidiasis in Patients Undergoing Prophylactic Treatment with Probiotic and Placebo During the 6 Months

This is a randomized, double-blind, clinical/comparative trial study, involving the recurrence of vaginal candidiasis (VVC) after initial treatment with oral fluconazole in patients undergoing prophylactic management with a probiotic and placebo for 6 months. Fifty-nine VVC patients who were diagnosed based on their history, physical examination, and culture of vaginal discharge were initially treated by a single dose of 150 mg fluconazole. According to the table of random numbers, the sample was divided into two groups. The patients from one group took probiotics, while those from the other group took a placebo, with all of them being continuously monitored for 6 months. The patients complaining of vaginal candidiasis symptoms, such as burning, pruritus, and a vaginal (curd-like) discharge, were examined and the discharge was cultured for candida. The positive cultures were considered to be recurring for the patients in each group. Thirty-one cases from the placebo group and 28 cases from the probiotic group were carefully observed. In total, the 6-month recurrence in the control group was eleven (35.5 %) and in the research group was two (7.2 %). The results from Fisher’s exact test for the value p = 0.01 and OR 0.14 95 % CI (0.028–0.7) showed significant recurrence in the placebo group. The findings demonstrated that taking probiotics withazole antifungal drugs could be highly effective in treating VVC, resulting in a lower recurrence rate as well.     

Photoautotrophic cultivating options of freshwater green microalgal Chlorococcum humicola for biomass and carotenoid production

Photoautotrophic cultivation of Chlorococcum humicola was performed in batch and continuous modes in different cultivating system arrangements to compare biomass and carotenoids’ concentration and their productivities. Batch result from stirred tank and airlift photobioreactors indicated the positive effect of increasing light intensity on growth and carotenoid production, whereas the finding from continuous cultivation indicated that carotenoid enhancement preferred high light intensity and nitrogen-deficient environment. The highest biomass (1.31?±?0.04?g?L^?1) and carotenoid (4.59?±?0.06?mg?L^?1) concentration as well as the highest productivities, 0.46?g?L^?1 d^?1 for biomass and 1.61?mg?L^?1 d^?1 for carotenoids, were obtained when maintaining high light intensity of 10 klx, BG-11 medium and 2% (v/v) CO₂ simultaneously, while the highest carotenoid content (4.84?mg?g^?1) was associated with high light intensity and nitrogen-deficient environment, which was induced by feed-modified BG-11 growth medium containing nitrate 20 folds lower than the original medium. Finally, the cultivating system arranged into smaller stirred tank photobioreactors in series yielded approximately 2.5 folds increase in both biomass and carotenoid productivities relative to using single airlift photobioreactor with equivalent working volume and similar operating condition.     

<Emphasis Type="Italic">In vitro</Emphasis> susceptibility testing of <Emphasis Type="Italic">Microsporum gypseum</Emphasis> isolated from healthy cattle and soil samples against itraconazole,terbinafine, fluconazole and topical veterinarian drugs

The present study evaluated in vitro susceptibility testing of dermatophytes isolates from healthy cattle and soil samples against three antifungal agents and three topical veterinarian drugs. Itraconazole and terbinafine showed a higher in vitro fungicidal activity than fluconazole. The veterinarian drugs LEPECID^® and iodine 5% were more active in vitro than the UNGÜENTO^® spray. All drugs showed fungicidal activity against Microsporum gypseum, and they may be considered as efficient agents for the topical treatment of dermatophytoses in cattle.     

Phytodesalination of landfill leachate using Puccinellia nuttalliana and Typha latifolia

Abstract

Landfilling has been widely used for solid waste disposal; however, the generation of leachate can pose a major threat to the surrounding environment in the form of soil salinity. Two native plants of North America Puccinellia nuttalliana (alkaligrass) and Typha latifolia (cattail) were selected in this study to investigate bioaccumulation of sodium (Na⁺) and chloride (Cl^?) under controlled greenhouse conditions. The treatments include irrigation of the plants using fertilizer (F), landfill leachate (LL), and tap water (control, C). Plants cultivated after one season (12?weeks) were harvested by separating aboveground tissues and roots, and soil from each treatment was collected for analysis. The results show that alkaligrass irrigated with LL had 2.13% more biomass yield than control, but 17.63% less than that with F. However, cattail yielded 19.70% more biomass with the irrigation of LL than C and 3.04% less compared to F. Alkaligrass and cattail accumulated 6.85 and 7.00?g Na⁺/Kg biomass with the irrigation of LL, respectively. Alkaligrass and cattail irrigated with LL accumulated 120.14% and 94.47% more Cl^? than C. When alkaligrass and cattail were irrigated with LL, the electrical conductivity of soil was reduced by 71.70% and 45.36%, respectively. This study demonstrated that using North American native halophytes could be a cost-effective and promising approach for phytoremediation of landfill leachate.     

Prevalence of Candida nivariensis and Candida bracarensis in Vulvovaginal Candidiasis

Candida nivariensis and Candida bracarensis were isolated from patients with vulvovaginal candidiasis (VVC). Candida nivariensis and Candida bracarensis were found in presumptive Candida glabrata isolates, which were identified using the API Candida system. We retrospectively re-examined vaginal presumptive Candida glabrata isolates for Candida nivariensis and Candida bracarensis from January 1, 2003, through December 31, 2012, via detection of the ITS1 region and the 5.8S ribosomal RNA gene. Among 301 presumptive Candida glabrata isolates, 293 isolates were confirmed as C. glabrata (97.34 %), 7 isolates were identified as C. nivariensis (2.33 %) and 1 isolate was identified as C. bracarensis (0.33 %). The C. nivariensis and C. bracarensis isolates were confirmed by sequencing. All C. nivariensis isolates were susceptible to nystatin and susceptible or susceptible dose-dependent to fluconazole, itraconazole, miconazole, and clotrimazole. The C. bracarensis isolate was susceptible to nystatin and the tested azoles. Among the seven patients with VVC caused by C. nivariensis and who were treated with various antifungal agents, only one patient achieved mycological eradication at both the day 7–14 and day 30–35 follow-ups. The C. bracarensis isolate was isolated from a symptomatic pregnant woman; additional data for this patient were unavailable. We conclude that C. nivariensis and C. bracarensis existed in the vaginal samples of patients with VVC. Therapeutic efficacy in the patients with C. nivariensis was poor and inconsistent with the observed in vitro antifungal susceptibility, which requires further study.     

Diclofenac exhibits synergism with azoles against planktonic cells and biofilms of Candida tropicalis

Abstract

This study aimed to evaluate the effect of diclofenac on minimum inhibitory concentrations of antifungals against planktonic cells and biofilms of Candida tropicalis. Susceptibility testing of planktonic cells was evaluated using the broth microdilution assay and checkerboard method. Biofilm formation by C. tropicalis in the presence of diclofenac, alone or in combination with antifungals, was also evaluated, and scanning electron microscope (SEM) and confocal microscope (CLSM) analyses were performed. Diclofenac showed an MIC of 1024?μg?ml^?1 against planktonic cells. The MICs of fluconazole and voriconazole against azole-resistant isolates were reduced 8- to 32-fold and 16- to 256-fold, respectively, when in combination with diclofenac. When in combination with fluconazole or voriconazole, diclofenac reduced the antifungal concentration necessary to inhibit C. tropicalis biofilm formation. In conclusion, diclofenac presents synergism with fluconazole and voriconazole against resistant C. tropicalis strains and improves the activity of these azole drugs against biofilm formation.     

Application of hydrocyclone for separation of Pichia pastoris produced r-HBsAg from fermentation culture: impact of concentration and pressure on hydrocyclone performance

Abstract

Separation of biomass from culture media by centrifugation and then washing the biomass are mandatory steps in the fermentation process of recombinant Pichia pastoris expressed HBsAg intracellularly. Biomass has to be washed many times to eliminate the culture media residues thoroughly. In this study, we tried to develop the hydrocyclone as an alternative method for separation of biomass from fermentation culture, an attractive replacement for centrifugation processes. The advantages of using hydrocyclone in biomass separation could be summarized in its suitability for continuous separation and its low risk of contamination. To evaluate the performance of hydrocyclone, concentration ratio in underflow to feed stream, capacity, and centrifugal force by considering three parameters of pressure drop, concentration, and the type of hydrocyclone were investigated.

Using three level factorial design a concentration ratio equation was developed, with the correlation coefficient R² = 0.977 ensured the good fitness of the predicted data with the experimental results. In optimal conditions, maximum concentration ratio was 1.246, for flow rate 13.5 LPM and C-force equal to 1276.11 at maximum pressure drop (3?bar) and minimum concentration (0.5% w/w) in hydrocyclone 1. Herein, two different hydrocyclones with the cylindrical diameters of 19?mm and 21?mm were used for separating the yeast cells.     

Characterization of polymicrobial biofilms obtained from saliva or carious lesions in dentin

Abstract

This study aimed to compare the formation of polymicrobial biofilms using carious dentin or saliva as inoculum for application in in vitro microbiological studies on caries research. For biofilm growth, combined samples of infected dentin or saliva from three donors were used. The biofilms were grown on glass coverslips, under a regimen of intermittent exposure (6?h day^?1) to 1% sucrose for 4?days. Total bacterial loads, as well as specific aciduric bacteria and mutans streptococci loads were quantified and correlated with biofilm acidogenicity and susceptibility to chlorhexidine. The data were evaluated using the Student’s-t, Mann Whitney and Kruskal-Wallis tests. The two biofilms showed similar microbial loads (total bacteria, aciduric bacteria and mutans streptococci) on day 4, and high acidogenicity after 48?h and were susceptible to chlorhexidine at different time intervals. In conclusion, both dentin and saliva can be used as an inoculum in in vitro studies of processes related to biofilm formation.     

The influence of light conditions and interspecific competition on the root foraging traits and seedling growth of two tree species

Abstract

Enriched nutrient patches within natural soil represent an important source of nutrients for tree growth. In the present study, pot experiments in a heterogeneous nutrient environment were conducted to investigate the influence of light conditions and interspecific competition on the root foraging traits and seedling growth of Pinus massoniana and Schima superba. The root foraging scale and the whole-seedling biomass of both species were decreased by shading. The result of this treatment was a lower sensitivity to nutrient heterogeneity in plants that underwent the shading treatment than in plants that were exposed to full-light conditions. The above-ground biomass and whole-seedling biomass of S. superba were not affected by competition with P. massoniana. In contrast, the above-ground biomass and whole-seedling biomass of P. massoniana were negatively affected by competition with S. superba. The more rapid rate of root extension and the more efficient resource uptake of S.superba appear to explain this effect. The species-specific patterns of the influence of environmental factors on foraging ability and seedling growth should be given thorough consideration and should be applied to afforestation and to the management of tree plantations.