Changes In Microenvironmental Conditions Research Articles

Assessment of Growth and Yield Characteristics of a Greenhouse Hybrid and a Dual-Purpose Tomato Cultivar under Different Microclimatic Conditions

Tomato (Solanum lycopersicum L., family Solanaceae) represents one of the most cultivated horticultural crops worldwide. It contains various nutrients, providing health benefits. For better crop management strategies, especially with global warming, it is crucial to investigate how varieties or cultivars bred for different purposes respond to the changing macro or microenvironmental conditions. This research aimed to assess the growth, reproductive development and selected quality parameters of two tomato varieties, ‘Sylviana’ (a greenhouse hybrid) and ‘Bolseno’ (a dual-purpose variety), under a greenhouse environment. The study was conducted in the mid-country wet zone of Sri Lanka where the intensive-control greenhouse (T1) maintained a favourable air temperature (<33°C) for crop growth compared to high daytime temperatures of semi-intensive (T2) and less-intensive (T3) greenhouses (up to 36°C). In ‘Bolseno’, vegetative growth parameters were significantly affected (P<0.05) by different environments but not in ‘Sylviana’ (P>0.05). T1 resulted in the highest mean fruit weight and mean fruit diameter in both varieties. Since ‘Sylviana’ performed well in all three growing environments, the fruit quality was assessed by measuring the antioxidant activity (AOX) and total phenolic content (TPC) using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay and Folin–Ciocalteu method, respectively. Significantly higher AOX (P<0.05) was reported in T1 while T2 had a higher TPC. The results revealed that different tomato genotypes respond differently to changes in micro environmental conditions in terms of growth and some reproductive traits, and the same variety grown in different conditions had different TPC and AOX.

Applications of Exosome Vesicles in Different Cancer Types as Biomarkers.

One of the biggest challenges in the fight against cancer is early detection. Early diagnosis is vital, but there are some barriers such as economic, cultural, and personal factors. Considering the disadvantages of radiological imaging techniques or serological analysis methods used in cancer diagnosis, such as being expensive, requiring expertise, and being time-consuming, there is a need to develop faster, more reliable, and cost-effective diagnostic methods for use in cancer diagnosis. Exosomes, which are responsible for intercellular communication with sizes ranging from 30-120 nm, are naturally produced biological nanoparticles. Thanks to the cargo contents they carry, they are a potential biomarker to be used in the diagnosis of cancer. Exosomes, defined as extracellular vesicles of endosomal origin, are effective in cancer growth, progression, metastasis, and drug resistance, and changes in microenvironmental conditions during tumor development change exosome secretion. Due to their high cellular activity, tumor cells produce much higher exosomes than healthy cells. Therefore, it is known that the number of exosomes in body fluids is significantly rich compared to other cells and can act as a stand-alone diagnostic biomarker. Cancer- derived exosomes have received great attention in recent years for the early detection of cancer and the evaluation of therapeutic response. In this article, the content, properties, and differences of exosomes detected in common types of cancer (lung, liver, pancreas, ovaries, breast, colorectal), which are the leading causes of cancer-related deaths, are reviewed. We also discuss the potential utility of exosome contents as a biomarker for early detection, which is known to be important in targeted cancer therapy.

Microbiome of the skin: The good and the bad

Microbiome of the skin: The good and the bad Chronic wounds are a significant burden to patients and health systems; Manuela Martins-Green from the University of California tells us how her research in understanding the dynamics of wound healing could aid new approaches to wound care. The skin is the largest organ in the human body. It is the barrier that protects the organs from the environment, functioning as an interface between the environment and the inside of the body. Residing on the skin is a complex and diverse community of microbes called the microbiome. Trillions of microbes across bacterial and fungal families use a wide range of aerobic and anaerobic metabolic pathways to survive. Considerable effort is being put into studying the role of the microbiome in skin infections, disorders, and disease. Host- microbiome interactions are particularly important during wound healing because changes in microenvironmental conditions in the tissue can change commensal bacteria into pathogens that infect the wound chronically, including forming biofilm.

The role of dung beetles in seed dispersal in an arid environment

Dung beetles can influence seedling emergence and survival. However, the direction and magnitude of this effect will depend on the functional traits of the dung beetle community and on the prevailing environmental conditions. We studied the role of dung beetles in seed dispersal of Prosopis flexuosa DC. in an arid environment. We conducted an experimental study to assess how different dung beetle species differ in their effectiveness as secondary seed dispersers. To evaluate this question, we selected four species belonging to three functional groups: lifters, tunnelers, and rollers. Dung beetles removed 0.7%-7.5% of the seeds embedded in cow dung. The net effect of beetles on seedling emergence and survival varied markedly among species: Malagoniella puncticollis (roller) had neutral effects on seedling emergence and positive in their survival. Sulcophanaeus imperator, Digitonthophagus gazella (tunneler) and Eucranium arachnoides (lifters) species had positive effect on seedling emergence. However, the effect of S. imperator on seedling survival was negative, and those of D. gazella and E. arachnoides, neutral. Our results indicate that although dung beetles remove few seeds of P. flexuosa, their main role consisted in producing changes in micro-environmental conditions for the seeds that remained in the dung pile.

P73 isoforms meet evolution of metastasis.

Cancer largely adheres to Darwinian selection. Evolutionary forces are prominent during metastasis, the final and incurable disease stage, where cells acquire combinations of advantageous phenotypic features and interact with a dynamically changing microenvironment, in order to overcome the metastatic bottlenecks, while therapy exerts additional selective pressures. As a strategy to increase their fitness, tumors often co-opt developmental and tissue-homeostasis programs. Herein, 25years after its discovery, we review TP73, a sibling of the cardinal tumor-suppressor TP53, through the lens of cancer evolution. The TP73 gene regulates a wide range of processes in embryonic development, tissue homeostasis and cancer via an overwhelming number of functionally divergent isoforms. We suggest that TP73 neither merely mimics TP53 via its p53-like tumor-suppressive functions, nor has black-or-white-type effects, as inferred by the antagonism between several of its isoforms in processes like apoptosis and DNA damage response. Rather, under dynamic conditions of selective pressure, the various p73 isoforms which are often co-expressed within the same cancer cells may work towards a common goal by simultaneously activating isoform-specific transcriptional and non-transcriptional programs. Combinatorial co-option of these programs offers selective advantages that overall increase the likelihood for successfully surpassing the barriers of the metastatic cascade. The p73 functional pleiotropy-based capabilities might be present in subclonal populations and expressed dynamically under changing microenvironmental conditions, thereby supporting clonal expansion and propelling evolution of metastasis. Deciphering the critical p73 isoform patterns along the spatiotemporal axes of tumor evolution could identify strategies to target TP73 for prevention and therapy of cancer metastasis.

How wind acclimation impacts Pinus pinaster growth in comparison to resource availability

Abstract Key message Anthropic and natural disturbances in Pine pinaster forests may induce changes in tree wind exposure and resource availability. The wind acclimation has consequences on P. pinaster growth comparable to resource acquisition after sudden changes in micro-environmental conditions. Context More disturbances occur within the forest, resulting in the creation of inter-tree space. This increases resource availability for the remaining trees but also their wind exposure. Trees have the ability to acclimate to these changes in their micro-environmental conditions by modifying their development. Increase in both resource availability and wind-induced deformations (strains) are known to promote tree radial growth but their relative importance has not been previously analysed in field conditions. Aims This paper aims to study the Pinus pinaster growth in response to a sudden change in wind loading in comparison to a rapid increase in resource availability. Methods An experiment was established in a 16-year-old P. pinaster to create different conditions of wind loading and resources by guying trees with wires and removing their neighbours. The increase in trunk volume below 4 m was monitored for 3 years by measuring the stem radial growth at three stem heights. Results Acclimation to wind has important consequences for stem growth, comparable to that of the effect of greater resource availability after an increase in inter-tree spacing. The increase in trunk volume below 4 m induced by wind and by having more resources were quantitatively close and were equivalent after 3 years of treatment, to the trunk volume increase during the year before experiment. The observed wind acclimation was interpreted in terms of tree mechanical reinforcement by calculating the gain in the stem flexural rigidity: mechanical strength gains of 13.8 and 20.3% of swaying trees were observed in comparison to guyed trees for both high and low resource levels, respectively. Our analysis suggests that the relative effects of wind loading or higher resource are not modified over time by seasonable growth modulation. Both the effects of the wind acclimation and the higher resource were found to be independent and are likely to be cumulative. Conclusion This study highlights the importance of considering wind acclimation in the regulation of growth in forests after a sudden change in environmental conditions.

Initial cell density encodes proliferative potential in cancer cell populations

Individual cells exhibit specific proliferative responses to changes in microenvironmental conditions. Whether such potential is constrained by the cell density throughout the growth process is however unclear. Here, we identify a theoretical framework that captures how the information encoded in the initial density of cancer cell populations impacts their growth profile. By following the growth of hundreds of populations of cancer cells, we found that the time they need to adapt to the environment decreases as the initial cell density increases. Moreover, the population growth rate shows a maximum at intermediate initial densities. With the support of a mathematical model, we show that the observed interdependence of adaptation time and growth rate is significantly at odds both with standard logistic growth models and with the Monod-like function that governs the dependence of the growth rate on nutrient levels. Our results (i) uncover and quantify a previously unnoticed heterogeneity in the growth dynamics of cancer cell populations; (ii) unveil how population growth may be affected by single-cell adaptation times; (iii) contribute to our understanding of the clinically-observed dependence of the primary and metastatic tumor take rates on the initial density of implanted cancer cells.

Effects of environmental variables and foliar traits on the transpiration rate of cocoa (Theobroma cacao L.) under different cultivation systems

The response of plant species to environmental conditions influences changes in functional traits associated with the process that determines biological fitness and ecosystem processes. However, documenting these responses remain largely elusive in cultivation systems. We analyzed how environmental variables and leaf traits have effects on the transpiration rate of cocoa (Theobroma cacao L.) trees compared among different cultivation systems. Fieldwork was carried out at the Sara Ana experimental station in Alto Beni, La Paz, Bolivia. We sampled four trees in each of eight plots; four plots for each cultivation system (organic monoculture vs. organic agroforestry). From each tree, two mature, sunlit and healthy leaves were collected to make measurements of foliar traits and environmental variables. We found that canopy cover was higher in the agroforestry system. The specific leaf area was greater in agroforestry but the stomata size was significantly higher in the monoculture system. Temperature had a positive relationship with transpiration, whereas canopy cover and specific leaf area had a negative relationship in the agroforestry system. Cultivation system caused changes in microenvironmental conditions and on the expression of leaf traits that regulate water flow through the plant. Thus, the mutual effects of canopy cover, larger leaves and smaller stomatal size may drive a more efficient water use by reducing the transpiration rate of plants growing in agroforestry systems.

Hypoxia-Induced Adaptations of miRNomes and Proteomes in Melanoma Cells and Their Secreted Extracellular Vesicles.

Reduced levels of intratumoural oxygen are associated with hypoxia-induced pro-oncogenic events such as invasion, metabolic reprogramming, epithelial–mesenchymal transition, metastasis and resistance to therapy, all favouring cancer progression. Small extracellular vesicles (EV) shuttle various cargos (proteins, miRNAs, DNA and others). Tumour-derived EVs can be taken up by neighbouring or distant cells in the tumour microenvironment, thus facilitating intercellular communication. The quantity of extracellular vesicle secretion and their composition can vary with changing microenvironmental conditions and disease states. Here, we investigated in melanoma cells the influence of hypoxia on the content and number of secreted EVs. Whole miRNome and proteome profiling revealed distinct expression patterns in normoxic or hypoxic growth conditions. Apart from the well-known miR-210, we identified miR-1290 as a novel hypoxia-associated microRNA, which was highly abundant in hypoxic EVs. On the other hand, miR-23a-5p and -23b-5p were consistently downregulated in hypoxic conditions, while the protein levels of the miR-23a/b-5p-predicted target IPO11 were concomitantly upregulated. Furthermore, hypoxic melanoma EVs exhibit a signature consisting of six proteins (AKR7A2, DDX39B, EIF3C, FARSA, PRMT5, VARS), which were significantly associated with a poor prognosis for melanoma patients, indicating that proteins and/or miRNAs secreted by cancer cells may be exploited as biomarkers.

Glucose Depletion Enhances the Stem Cell Phenotype and Gemcitabine Resistance of Cholangiocarcinoma Organoids through AKT Phosphorylation and Reactive Oxygen Species.

Cancer cells are strongly dependent on the glycolytic pathway for generation of energy even under aerobic condition through a phenomenon known as the Warburg effect. Rapid proliferation of cancer cells is often accompanied by high glucose consumption and abnormal angiogenesis, which may lead to glucose depletion. In the present study, we investigated how cholangiocarcinoma cells adapt to glucose depletion using a 3D organoid culture system. We cultured organoids derived from cholangiocarcinoma under glucose-free condition and investigated cell proliferation, expression of stem cell markers and resistance to gemcitabine. Cholangiocarcinoma organoids cultured under glucose-free condition showed reduced proliferation but were able to survive. We also observed an increase in the expression of stem cell markers including LGR5 and enhancement of stem cell phenotypic characteristics such as resistance to gemcitabine through AKT phosphorylation and reactive oxygen species. These findings indicate that cholangiocarcinoma cells are able to adapt to glucose depletion through enhancement of their stem cell phenotype in response to changes in microenvironmental conditions.

STEM-09. INTRINSIC TUMOR PLASTICITY IN GLIOBLASTOMA ALLOWS FOR RECREATION OF STEM LIKE-STATES AND EFFICIENT TUMOR CELL ADAPTATION TO NEW MICROENVIRONMENTS

Abstract BACKGROUND Cellular heterogeneity is a hallmark of numerous cancer types, including Glioblastoma (GBM). Cancer stem cells (CSC) have been accounted for the generation of phenotypic heterogeneity and tumor progression in GBM. Recent data, however, suggest that CSCs may not represent a stable entity and intrinsic plasticity plays a key role in tumor adaptation to changing microenvironments. The question arises whether CSCs are a defined subpopulation of GBM or whether they represent a cellular state that any cancer cell can adopt. METHODS We interrogated intra-tumoral phenotypic heterogeneity at the single cell transcriptomic and proteomic level in GBM biopsies, patient-derived stem-like cultures and orthotopic xenografts (PDOXs). Tumor cell subpopulations, classified based on their expression of four proposed stem cell markers (CD133, CD15, A2B5 and CD44), were FACS isolated and functionally characterized under various microenvironmental conditions. Mathematical Markov modelling was applied to calculate state transitions. RESULTS GBM patient biopsies, PDOXs and stem-like cell cultures displayed remarkable stem cell-associated intra-tumoral heterogeneity. However independent of marker expression, all analysed tumor subpopulations carried stem-cell properties and recreated phenotypic heterogeneity. Mathematical modeling revealed a different propensity in reforming heterogeneity over time, which was independent of the proliferation index but linked to in vivo tumorigenic potential. Although GBM subpopulations varied in their potential to adapt to new environments, all were able to reach a steady state microenvironment-specific equilibrium. CONCLUSIONS Our results suggest that phenotypic heterogeneity in GBM results from intrinsic plasticity allowing tumor cells to adapt to changing microenvironmental conditions. Cellular states are non-hierarchical, reversible and occur via stochastic state transitions, striving towards a microenvironment-instructed equilibrium. Our data provides evidence that CSCs do not represent a defined clonal entity, but rather a cellular state determined by environmental conditions, which has implications for the design of treatment strategies targeting CSC-like states.

Microenvironment-Driven Dynamic Heterogeneity and Phenotypic Plasticity as a Mechanism of Melanoma Therapy Resistance.

Drug resistance constitutes a major challenge in designing melanoma therapies. Microenvironment-driven tumor heterogeneity and plasticity play a key role in this phenomenon. Melanoma is highly heterogeneous with diverse genomic alterations and expression of different biological markers. In addition, melanoma cells are highly plastic and capable of adapting quickly to changing microenvironmental conditions. These contribute to variations in therapy response and durability between individual melanoma patients. In response to changing microenvironmental conditions, like hypoxia and nutrient starvation, proliferative melanoma cells can switch to an invasive slow-cycling state. Cells in this state are more aggressive and metastatic, and show increased intrinsic drug resistance. During continuous treatment, slow-cycling cells are enriched within the tumor and give rise to a new proliferative subpopulation with increased drug resistance, by exerting their stem cell-like behavior and phenotypic plasticity. In melanoma, the proliferative and invasive states are defined by high and low microphthalmia-associated transcription factor (MITF) expression, respectively. It has been observed that in MITFhigh melanomas, inhibition of MITF increases the efficacy of targeted therapies and delays the acquisition of drug resistance. Contrarily, MITF is downregulated in melanomas with acquired drug resistance. According to the phenotype switching theory, the gene expression profile of the MITFlow state is predominantly regulated by WNT5A, AXL, and NF-κB signaling. Thus, different combinations of therapies should be effective in treating different phases of melanoma, such as the combination of targeted therapies with inhibitors of MITF expression during the initial treatment phase, but with inhibitors of WNT5A/AXL/NF-κB signaling during relapse.

Fibronectins: Structural-functional relationships

This review summarized current data on the structure of fibronectin (FN), a multifunctional glycoprotein of vertebrates. FN is not only a permanent component of the extracellular matrix (ECM) but also an important regulator of cell functions via transformation of the ECM composition and organization and/or interaction with receptor and other membranebound cell proteins. Multifunctionality of FN owes hierarchical relationships between its structuralfunctional determinants, which comprise the linear ones (FN peptide fragments), association zones (surface contacts between the FN molecule and a FN-associated protein) and functional domains (those binding fibrin, heparin, gelatin and integrins). The modular architectonic principle of FN organization is pivotal to intrinsic adaptation of this glycoprotein to changing microenvironmental conditions. We also discuss the issue of key stages of FN fibrillogenesis with a special focus on the molecular mechanisms that underlie polymerization of FN molecules.

Tree species diversity affects decomposition through modified micro-environmental conditions across European forests.

Different tree species influence litter decomposition directly through species-specific litter traits, and indirectly through distinct modifications of the local decomposition environment. Whether these indirect effects on decomposition are influenced by tree species diversity is presently not clear. We addressed this question by studying the decomposition of two common substrates, cellulose paper and wood sticks, in a total of 209 forest stands of varying tree species diversity across six major forest types at the scale of Europe. Tree species richness showed a weak but positive correlation with the decomposition of cellulose but not with that of wood. Surprisingly, macroclimate had only a minor effect on cellulose decomposition and no effect on wood decomposition despite the wide range in climatic conditions among sites from Mediterranean to boreal forests. Instead, forest canopy density and stand-specific litter traits affected the decomposition of both substrates, with a particularly clear negative effect of the proportion of evergreen tree litter. Our study suggests that species richness and composition of tree canopies modify decomposition indirectly through changes in microenvironmental conditions. These canopy-induced differences in the local decomposition environment control decomposition to a greater extent than continental-scale differences in macroclimatic conditions.

Vegetation response to logging residue removals in Great Lakes aspen forests: Long-term trends under operational management

Conservation of vegetation diversity has been integrated into forest management regimes as stands with high levels of diversity have been shown to possess enhanced ecological services and resilience to disturbance. Effects of intensified forest management and harvesting practices such as logging residue removals for bioenergy on vegetation diversity and community dynamics has been largely overlooked, however. We examined forest vegetation communities under residue removal treatments along a unique 40-yr chronosequence of commercial aspen (Populus spp.) in Upper Michigan to examine potential impacts on species abundance metrics, community structure, and heterogeneity. We hypothesized that residue removals would negatively impact species diversity of both the over- and understory communities, and that these patterns would occur in parallel with shifts in community structure of both strata. Our results show no effect of residue treatment on overstory tree communities; however we did observe an increase in understory species richness, diversity, and evenness in stands where residues were harvested. The understory community structure was correlated with soil total nitrogen levels, yet this pattern was independent of harvest residue treatment. In addition, we observed higher levels of variance in species representation of the understory community when residues were removed, but did not detect any difference in community organization. Overall, our results suggest that the removal of harvest residues can increase variability in vegetation community relationships. We believe that these patterns can be attributed to increased site disturbance and soil scarification through additional equipment trafficking and subsequent changes in micro environmental conditions when residues are harvested.

An Emerging Allee Effect Is Critical for Tumor Initiation and Persistence.

Tumor cells develop different strategies to cope with changing microenvironmental conditions. A prominent example is the adaptive phenotypic switching between cell migration and proliferation. While it has been shown that the migration-proliferation plasticity influences tumor spread, it remains unclear how this particular phenotypic plasticity affects overall tumor growth, in particular initiation and persistence. To address this problem, we formulate and study a mathematical model of spatio-temporal tumor dynamics which incorporates the microenvironmental influence through a local cell density dependence. Our analysis reveals that two dynamic regimes can be distinguished. If cell motility is allowed to increase with local cell density, any tumor cell population will persist in time, irrespective of its initial size. On the contrary, if cell motility is assumed to decrease with respect to local cell density, any tumor population below a certain size threshold will eventually extinguish, a fact usually termed as Allee effect in ecology. These results suggest that strategies aimed at modulating migration are worth to be explored as alternatives to those mainly focused at keeping tumor proliferation under control.

Differences in the facilitative ability of two Mediterranean shrubs on holm-oak seedling recruitment in Mediterranean savanna-forest ecosystems

This paper analyses the nurse effect of Cistus salvifolius and Myrtus communis on holm-oak seedling recruitment in Mediterranean savanna-like ecosystems. Changes in microenvironmental conditions beneath the shrubs canopies, leaf phenology and nurse effect of the two shrubs on holm-oak seedlings emergence and survival in the field were studied. C. salvifolious exhibited a null effect on holm-oak seedlings recruitment in the field, showed a high seasonal variability in leaf area (52% decrease during summer), and high variability in photosynthetic photon flux density (PPF) beneath the understory. By contrast, M. communis exhibited the opposite characteristics: had a positive effect on holm-oak seedlings recruitment in the field and showed big changes on air temperature and PPF beneath the understory (94% reduction), small seasonal variability in leaf area, and small variability in PPF beneath the understory. It is discussed that grazing abandonment that leads to the expansion of C. salvifolus and other early succesional chamephites does not guarantee sexual self-regeneration of holm-oaks in dehesas. Strategies to enhance late-successional evergreen and some different potentially occurring, pioneer shrub species that facilitate holm-oak seedling recruitment should be taken into account.

Glucose-Based Regulation of miR-451/AMPK Signaling Depends on the OCT1 Transcription Factor

In aggressive, rapidly growing solid tumors such as glioblastoma multiforme (GBM), cancer cells face frequent dynamic changes in their microenvironment, including the availability of glucose and other nutrients. These challenges require that tumor cells have the ability to adapt in order to survive periods of nutrient/energy starvation. We have identified a reciprocal negative feedback loop mechanism in which the levels of microRNA-451 (miR-451) are negatively regulated through the phosphorylation and inactivation of its direct transcriptional activator OCT1 by 5' AMP-activated protein kinase (AMPK), which is activated by glucose depletion-induced metabolic stress. Conversely, in a glucose-rich environment, unrestrained expression of miR-451 suppresses AMPK pathway activity. These findings uncover miR-451 as a major effector of glucose-regulated AMPK signaling, allowing tumor cell adaptation to variations in nutrient availability in the tumor microenvironment.

RETRACTED: Macrophage phenotypic plasticity in atherosclerosis: The associated features and the peculiarities of the expression of inflammatory genes

Macrophages are essential players in induction and progression of atherosclerotic inflammation. The complexity of macrophage phenotypes was observed in human plaques and atherosclerotic lesions in mouse models of atherosclerosis. Plaque macrophages were shown to exhibit a phenotypic range that is intermediate between two extremes, M1 (pro-inflammatory) and M2 (anti-inflammatory). Indeed, in atherosclerosis, macrophages demonstrate phenotypic plasticity to rapidly adjust to changing microenvironmental conditions. In the plaque, serum lipids, serum lipoproteins and various pro- or anti-inflammatory stimuli such as cytokines, chemokines and small bioactive molecules could greatly influence the macrophage phenotype inducing switch towards more proinflammatory or anti-inflammatory properties. Dynamic plasticity of macrophages is achieved by up-regulation and down-regulation of an overlapping set of transcription factors that drive macrophage polarization. Understanding of mechanisms of macrophage plasticity and resolving functional characteristics of distinct macrophage phenotypes should help in the development of new strategies for treatment of chronic inflammation in atherosclerosis and other cardiovascular diseases.

Descomposición de hojarasca de las especies leñosas nativas y exóticas más abundantes del pedemonte de las Yungas, Tucumán, Argentina

Ecologia Austral, 24:286-293 (2014) Exotic species may influence the process of decomposition, either directly (through differences in the quality and/or quantity of leaf-litter) or indirectly (by altering microclimatic conditions and the abundance and/or activity of decomposers). The aims of our study were: I) to compare the decomposability of the most abundant exotic and native species in secondary forests of the Sierra de San Javier, Tucuman, II) to assess the effect of the environment on the rate of decomposition of an homogeneous substrate and III) to evaluate the effect of the litterbags mesh size on the decomposition process. To do this, we incubated leaf-litter of 7 native and 7 exotic species under standard conditions for one year and also leaf-litter of Populus deltoides (homogeneous substrate) in native and invaded by Ligustrum lucidum secondary forest patches in bags with two mesh sizes. Native and exotic species did not differ in their weight loss rates, but there were interspecific differences. The decay constant of the homogeneous substrate was lower in invaded patches so it is possible that L. lucidum modify the composition and /or activity of decomposing organisms and generate changes in micro-environmental conditions. In addition, decomposition was higher in bags with larger mesh size. This pattern may be explained by the differential access of macro invertebrates. Our results suggest the absence of a pattern of decay in native and exotic species as groups, and the potential influence that L. lucidum would have over the factors controlling littler decomposition.