Data are from publication: Lenda, M., Steudel, B., Skórka, P. et al. Multiple invasive species affect germination, growth, and photosynthesis of native weeds and crops in experiments. Sci Rep 13, 22146 (2023). https://doi.org/10.1038/s41598-023-48421-w
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The study titled "Multiple invasive species affect germination, growth, and photosynthesis of native weeds and crops in experiments" aimed to investigate the combined effects of two invasive plant species—Persian walnut (Juglans regia) and Canadian goldenrod (Solidago canadensis)—on the germination, growth, and photosynthetic performance of native weeds and crops in European agricultural fields.
Aim of the Study The primary objective was to test the hypothesis that extracts from these invasive species, both individually and in combination, would have detrimental effects on crops and weeds, potentially exhibiting additive or synergistic interactions.
Methods
The study comprised three main experimental stages designed to evaluate the effects of walnut and goldenrod extracts on native and crop plants, conducted between May and July 2014.
1. Petri Dish Germination Experiment Objective: To assess how walnut, goldenrod, and combined extracts affect the germination rate of seeds.
Procedure: Seeds of four crop species (Brassica oleracea, Fagopyrum esculentum, Lupinus albus, and Triticum aestivum) and four weed species (Campanula patula, Coronilla varia, Matricaria chamomilla, and Trifolium repens) were placed in Petri dishes lined with blotting paper. Each dish received 3 ml of one of four treatments: distilled water (control), goldenrod extract, walnut extract, or a combination of goldenrod and walnut extracts. Petri dishes were maintained with regular watering using filtered tap water.
Data Collection:
The we monitored daily for germination, defined as radicle growth of 1 mm or more. Germination percentage was calculated for each species and treatment.
2. Greenhouse Flowerpot Experiment Objective: To assess seedling growth in response to walnut, goldenrod, and mixed extracts in a controlled greenhouse environment.
Procedure:
This phase involved three crop species (Fagopyrum esculentum, Lupinus albus, Triticum aestivum) and four weed species (Agrostemma githago, Cichorium intybus, Matricaria chamomilla, and Trifolium repens). Seeds were planted in 5x5x5 cm flowerpots containing commercially available soil and watered with 25 ml of the respective treatment once.
Data Collection: Growth metrics, including seedling height and number of leaves, were recorded at two and four weeks. After four weeks, seedlings were thinned to one per pot, and both above- and below-ground biomass were measured. The soil and environmental conditions in the greenhouse were controlled, with natural light exposure and temperature regulation to reflect outdoor conditions.
3. Photosynthetic Efficiency Measurements Objective: To assess the impact of allelopathic compounds on photosynthetic health.
Procedure:
Following the four-week growth period, chlorophyll fluorescence parameters and total chlorophyll content were measured. This included: Maximum Efficiency of PS II (Fv/Fm): Indicates the plant's photosynthetic efficiency.
Photochemical Quenching (qP) and Non-Photochemical Quenching (NPQ): Reflect how plants manage light energy.
Greenness Index: Measured chlorophyll content to indicate the health and vitality of the plants.
Equipment: Measurements were conducted with an FMSII pulse-amplitude-modulated fluorometer, using specific light conditions to simulate natural settings.
Dataset The data collected includes various plant performance indicators from both crop and weed species under different treatments:
Petri Dish Experiment Data: Seed germination rates for each species under each treatment. The dataset includes both the raw number of germinated seeds and calculated germination percentages for each species and treatment combination.
Greenhouse Flowerpot Experiment Data: Measurements of seedling height, leaf count, and biomass (above- and below-ground) at multiple time points. Survival rates, noting whether seedlings survived at two and four weeks. Relative root biomass (calculated as the root biomass divided by the total plant biomass) to provide insight into root-to-shoot allocation as a response to allelopathic stress.
Photosynthetic Efficiency Data: Measurements of chlorophyll fluorescence indicators (Fv/Fm, qP, NPQ) and the greenness index for each species and treatment group. These metrics provide insight into photosynthetic health and the biochemical responses of plants exposed to allelopathic compounds.
Statistical Analyses
Data were analyzed using Generalized Linear Mixed Models (GLMMs), which allowed for the assessment of treatment effects on variables like germination, growth, and photosynthetic efficiency. Random factors included species nested within plant type (crop or weed), and flowerpot identity was also considered in the greenhouse data analysis. This dataset, with recorded growth, survival, and physiological measurements, enables a thorough analysis of how allelopathic compounds impact both native weeds and crop species, revealing potential management strategies for invasive species in agricultural landscapes.
Results:
The study results highlighted how walnut and goldenrod extracts, individually and in combination, affected the germination, growth, biomass, and photosynthetic efficiency of both crop and weed species. Here’s a breakdown of the findings:
1. Germination (Petri Dish Experiment) Decreased Germination: Both goldenrod and walnut extracts individually reduced germination rates in all species compared to the control. No Synergistic Effect: The combined treatment (goldenrod + walnut) did not have a stronger effect on germination rates than the individual extracts alone. This suggested that the two extracts did not interact synergistically to increase allelopathic effects. Crop vs. Weed Response: Crops generally had lower germination rates than weeds under all treatments, indicating that crops might be more susceptible to allelopathic effects.
2. Seedling Growth and Biomass (Greenhouse Flowerpot Experiment) Reduced Growth: Seedlings treated with walnut, goldenrod, or combined extracts grew shorter and had fewer leaves compared to the control group. This effect was consistent across both crop and weed species. Biomass Reduction: Total Biomass: Both aboveground and root biomass were significantly lower in plants exposed to the extracts than in the control group, with goldenrod having a slightly stronger effect than walnut. Root Biomass: The extract-treated plants generally showed reduced root biomass. However, this reduction was less pronounced in weeds than in crops. Root-to-Shoot Allocation: Some species exhibited a higher proportion of root biomass relative to total biomass when treated with extracts, suggesting an adaptive response to the stress induced by allelopathic compounds.
3. Photosynthetic Efficiency Chlorophyll Fluorescence Indicators: Maximum Efficiency of PS II (Fv/Fm): The Fv/Fm ratio increased in extract-treated plants, indicating that the plants might be altering their photosynthetic mechanisms in response to allelopathic stress. Photochemical (qP) and Non-Photochemical Quenching (NPQ): The results for qP and NPQ varied by species, with crops showing higher photochemical quenching (qP) than weeds, suggesting a stress-induced enhancement in photosynthetic efficiency. Non-photochemical quenching (NPQ) also increased, indicating energy dissipation as a stress response. Greenness Index: The chlorophyll content, as measured by the greenness index, was slightly elevated in treated crops compared to weeds, likely as a compensatory mechanism in response to reduced growth.
4. Comparison of Crop and Weed Responses Greater Vulnerability of Crops: Crops generally exhibited stronger reductions in germination, growth, and photosynthetic performance than weeds across treatments, indicating a higher sensitivity to allelopathic effects. Resilience in Weeds: Weeds showed greater resilience, with relatively less reduction in biomass and photosynthetic performance compared to crops. This resilience may stem from their natural exposure to allelopathic interactions in their environments.
5. Lack of Synergistic Effects in Combined Extracts The combined goldenrod and walnut extracts did not exhibit a stronger inhibitory effect than the individual extracts alone. This suggests that, although both invasive species affect growth and physiology, their effects are not additive when they coexist.
