Progesterone (P4) antagonizes estradiol (E2) in synaptic remodeling in the hippocampus during the rat estrous cycle. To further understand how P4 modulates synaptic plasticity, we used entorhinal cortex lesions, which induce E2-dependent neurite sprouting in the hippocampus. In young ovariectomized rats, the E2-dependent entorhinal cortex lesion-induced sprouting was attenuated by concurrent treatment with P4 and E2. Microglial activation also showed the E2-P4 antagonism. These findings extend reports on the estrous cycle synaptic remodeling without lesions by showing the P4-E2 antagonism during simultaneous treatment with both E2 and P4. Glial mechanisms were analyzed with the wounding-in-a-dish model of cocultured glia and embryonic d-18 cortical neurons from rat. In cocultures of mixed glia (astrocytes plus 30% microglia), P4 antagonized the E2-dependent neurite outgrowth (number and length) and neuron viability in the presence of E2, as observed in vivo. However, removal of microglia (astrocyte-neuron coculture) abolished the antagonism of E2 by P4 on neuron sprouting. The P4 receptor antagonists ORG-31710 and RU-486 blocked the antagonism of P4 on E2-dependent sprouting. These findings suggest a new role for microglia in P4 antagonism of E2 in neuronal plasticity and show its dependence on progesterone receptors. These findings are also relevant to the inclusion of progestins in hormone therapy, which is controversial in relation to cognitive declines during aging and in Alzheimer's disease.

Global changes have altered the distribution pattern of the plant communities, including invasive species. Anthropogenic contamination may reduce native plant resistance to the invasive species. Thus, the focus of the current review is on the contaminant biogeochemical behavior among native plants, invasive species and the soil within the plant-soil ecosystem to improve our understanding of the interactions between invasive plants and environmental stressors. Our studies together with synthesis of the literature showed that a) the impacts of invasive species on environmental stress were heterogeneous, b) the size of the impact was variable, and c) the influence types were multidirectional even within the same impact type. However, invasive plants showed self-protective mechanisms when exposed to heavy metals (HMs) and provided either positive or negative influence on the bioavailability and toxicity of HMs. On the other hand, HMs may favor plant invasion due to the widespread higher tolerance of invasive plants to HMS together with the “escape behavior” of native plants when exposed to toxic HM pollution. However, there has been no consensus on whether elemental compositions of invasive plants are different from the natives in the polluted regions. A quantitative research comparing plant, litter and soil contaminant contents between native plants and the invaders in a global context is an indispensable research focus in the future.

Nitrogen (N) is one of the essential nutrients for plant growth. Appropriate application of N can improve the N use efficiency (NUE) and significantly promote plants’ growth. However, under N toxic conditions, the relationship between the growth and antioxidant system of invasive plants under different N forms and competitive treatments is not fully understood. Therefore, in this study, the performance of invasive species Wedelia trilobata and its native species Wedelia chinensis was evaluated under two sets of N forms and ratios, namely, NH4+-N(AN)/NO3–-N(NN) = 2:1 and NH4+-N(AN)/NO3–-N(NN) = 1:2 along with two intraspecific and interspecific competitions under without N and high N level of 15 g N⋅m–2 year–1, respectively. Data regarding the growth indices, antioxidant enzyme activities, including peroxidase (POD) and catalase (CAT), malondialdehyde (MDA), and proline contents were determined. Results showed that for competitive treatments, growth status was better for interspecific competition than intraspecific competition. The plant biomass of W. trilobata was significantly higher than that of W. chinensis. N significantly promoted the plants’ growth in terms of leaf area and biomass yield, and the antioxidant enzyme activities were significantly increased under a high N treatment than that of the control. Among N forms/ratios, ammonium N (AN)/nitrate N (NN) = 2:1 significantly enhanced the enzyme activity, particularly in W. trilobata. Furthermore, for intraspecific competition, MDA contents of W. trilobata were significantly decreased compared to that of W. chinensis. In conclusion, our results showed that W. trilobata adapted well under competitive conditions through better growth and antioxidant defense system.

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Aims Invasive alien plants cannot only decrease riparian vegetation diversity but also alter wetland ecosystem carbon processes, especially when they displace the original vegetation. Invasive Canada goldenrod (Solidago canadensis) has colonized large areas of disturbed and undisturbed land in southeastern China, yet little is known regarding how it affects soil carbon cycling. To explore the response patterns of soil respiration following S. canadensis invasion and their driving mechanisms, an observational field study and a greenhouse experiment simulating invasion were performed. Methods In the field study, soil respiration was measured weekly from 21 th of July to 15 th of December 2018. In the greenhouse experiment, soil respiration, autotrophic and heterotrophic respiration was measured every 1 st and 15 th of the month 15 th of July to 15 th of December 2019. Soil, autotrophic and heterotrophic respiration were measured using a closed-chamber system with the deep gauze collar root exclusion method. Important Findings Solidago canadensis invasion appeared to decrease the total soil CO2 emissions in both the field study and the greenhouse experiment. The suppressive effects on soil respiration may be attributed to S. canadensis invasion-induced alterations in the quality and quantity of available soil substrate, suggesting that S. canadensis invasion may impact soil carbon cycling via plant-released substrates and by competing for the soil available substrate with native plant and/or soil microbes. These results have substantial implications for estimations of the effects of invasive plants on belowground carbon dynamics and their contribution to the warming world.

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