Background This study was performed to characterize the metabolic, functional, and structural cardiac changes in a canine model of radiation‐induced heart disease by serial in vivo imaging and ex vivo analyses. Methods and Results Thirty‐six dogs were randomly assigned to control or irradiated groups at 3 time points (months 3, 6, and 12 after radiation; each group comprised 6 dogs). The left anterior myocardium of dogs in irradiated groups was irradiated locally with a single dose of 20‐Gy X‐ray. The irradiated myocardial regions showed increased myocardial uptake of 18 F‐FDG ( 18 F‐fludeoxyglucose) in the irradiated beagles, but the increased uptake area decreased at months 6 and 12 compared with month 3 after radiation. Abnormality of myocardial perfusion and cardiac function were detected at month 6 after radiation. Compared with the control groups, the protein expression of GLUT4 (glucose transporter 4) was upregulated in the irradiated groups, correlating with significantly decreased CPT1 (carnitine acyltransferase 1) expression. Mitochondria degeneration, swelling, and count reduction in the irradiated groups were observed. The difference in CD68 of macrophage markers and the inflammatory cytokines (IL‐6 [interleukin 6], TNF‐α [tumor necrosis factor α]) between the irradiation and control groups was not significant. Furthermore, the progressive aggravation of apoptosis and fibrosis was displayed. Conclusions Elevated 18 F‐FDG uptake occurred after irradiation and subsequently led to ventricular perfusion defects and dysfunction. The process was associated with myocardial metabolic substrate remodeling, cardiac muscle cell apoptosis, and myocardial fibrosis rather than inflammation.

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Allelochemicals released by invasive plants contribute to the successful invasion of new habitats. However, the relationship between allelopathic effects and competitive ability of invasive plants has not been characterized. We quantified the neighbor effects of Wedelia trilobata (family: Asteraceae) and the allelopathic effects of its leaf litter on two Asteraceae competitor species (invasive Eupatorium catarium and non‐invasive Lactuca sativa) and on its own ramet growth. The seed germination rate and seedling biomass of the two competitor species decreased following treatment with W. trilobata leaf extracts. When co‐cultured with W. trilobata, the total biomass of the two competitor species significantly decreased regardless of whether leaf extracts were present. Under low plant density co‐culture conditions, W. trilobata leaf extracts enhanced the inhibitory effects on E. catarium. In contrast, W. trilobata leaf extracts promoted the growth of W. trilobata adventitious roots, resulting in increased competitive ability. Therefore, W. trilobata growth was promoted by its own allelochemicals in leaf extracts, whereas the growth of the invasive and non‐invasive competitors was inhibited by the same chemicals. These responses facilitated the invasion by W. trilobata. Our study demonstrates that leaf litter of invasive plants may inhibit the growth of neighboring species to enhance the competitive ability of the invasive plants during the early stages of invasion.

The role of the interactions between endophytes and alien plants has been unclear yet in plant invasion. We used a completely germ-free culture system to quantify the plant growth-promoting (PGP) effects of endophytic bacteria Bacillus sp. on aseptic seedlings of Wedelia trilobata and of its native clonal congener W. chinensis. The endophytic bacteria did not affect the growth of W. chinensis, but they significantly promoted the growth of W. trilobata. With the PGP effects of endophytic bacteria, relative change ratios of the clonal traits and the ramets’ growth traits of W. trilobata were significantly greater than those of W. chinensis. Our results indicate that the growth-promoting effects of endophytes may differ between invasive and native clonal plants, and the endophytes of invasive plant may be host-specific to facilitate plant invasion.

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