Data for: Nanoparticles alter the nature and strength of intraploidy and interploidy interactions in plants
Description
Engineered nanoparticles have profound impacts on organisms, yet there is limited understanding of how nanoparticle exposure shapes species interactions that are key for natural community dynamics. By growing plants of the same (intraploidy) and different ploidy levels (interploidy) of Fragaria in axenic microcosms, we examined the influence of nanoparticles on species interactions in polyploid and diploid plants. Under copper oxide (CuO) nanoparticle exposure, polyploids experienced reduced competition and a shift towards facilitation, when growing with both polyploids (the effect of polyploids on polyploids measured by the relative interaction index, RII8x,8x) and diploids (the effect of diploids on polyploids, RII8x,2x). This reduction in competitive interactions in polyploids, in line with the stress gradient hypothesis, was primarily caused by nanoscale effects. In contrast, the strength of competitive interactions (RII8x,8x and RII8x,2x) increased under CuO bulk particles compared to control conditions. Different from polyploids, diploids experienced neutral interactions (RII2x,2x and RII2x,8x) under both nanoparticles and bulk particles. These findings underscore ploidy specific interaction dynamics and the need of considering species interactions when predicting organismal responses to nanoparticle pollution in ecological communities.
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To examine the intraploidy and interploidy interactions, we focused on diploid (2x) Fragaria viridis and octoploid (8x) Fragaria virginiana, two closely related wild strawberry species. F. viridis is thought to contribute to one of the four subgenomes of F. virginiana, as well as to the other octoploids including F. chiloensis and the cultivated strawberry (F. × ananassa), although this remains a subject of ongoing debate. Aseptic propagation of the plants was conducted in Murashige and Skoog Basal medium with vitamins and sucrose within glass culture tubes (25 mm × 150 mm) before the start of the competition experiment. The basic unit of the competition experiment consisted of five plant combinations: diploid growing alone (2x), diploid growing with intraploidy level (2x–2x), diploid and polyploid growing together (2x–8x), polyploid growing with intraploidy level (8x–8x), and polyploid growing alone (8x). The basic units of the competition experiment were subject to stress treatments (CuO nanoparticles, ‘NPs’; CuO bulk particles, ‘Bulk’; and control), with five replicates each treatment: 5 plant combinations × 3 stress treatments × 5 replicates, resulting in 75 total experimental microcosms. Before the start of the experiment, individual microcosms (55 mL glass tubes, 25 mm × 150 mm) were filled with 4 g Sunshine Redi-Earth Plug & Seedling Potting Mix and 4 mL of deionized (DI) water. These microcosms were autoclaved three times for 45 min each time. Then 1 mL of CuO nanoparticles (particle size <50 nm) or 1 mL of CuO bulk particles (particle size ~2000 nm), suspended in autoclaved DI water, was added into the NPs treatment (resulting in a final concentration of 100 ppm in microcosms, i.e., 100 mg kg-1) and the Bulk treatment (100 ppm), respectively. For the control treatment, 1 mL of autoclaved DI water was added. Following the preparation of microcosms, diploid and polyploid plants were transferred into individual microcosms under a sterile laminar flow hood. The microcosms were capped, and plants were grown under a light intensity of 50 μmol m-2 s-1 for 16 hours a day at 24 ºC. We ended the experiment after three weeks, because axenic microcosms without additional added water could experience increased evaporation over time. In this study, we measured the height of individual plants in the microcosms at both the beginning and end of the experiment. We evaluated the nature and intensity of plant–plant interactions using the relative interaction index (RII) that ranges between -1 and 1. A negative RII (< 0) indicates competition (with more negative values reflecting stronger competition), while a positive RII (> 0) indicates facilitation (with higher positive values reflecting stronger facilitation).