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. We found that, under copper oxide (CuO) nanoparticle exposure, polyploids experienced reduced competition when growing with polyploids (the effect of polyploids on polyploids, RII8x,8x), and a shift towards facilitation when growing with 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, because the strength of competitive interactions (RII8x,8x and RII8x,2x) remained relatively unchanged under CuO bulk particles compared to the control. In contrast, diploids experienced a shift from facilitation (RII2x,2x and RII2x,8x) under the control to neutrality under CuO nanoparticle exposure, with a similar reduction in facilitation observed with 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. 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. To minimize the potential influence of microenvironmental variation, microcosms were randomized daily. Because microcosms in sterile microcosms without additional added water could experience increased evaporation over time, we ended the experiment after three weeks to prevent potential stress confounding due to water loss. 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). The RII compares plant growth with competitors (Bw) and without competitors (Bo): RII = (Bw – Bo)/(Bw + Bo). In this study, we assessed plant growth using plant height as a proxy.