Invasive plants often express above-ground traits, such as higher growth than native plants, which promote their success. This may reflect low levels of invertebrate herbivory and/or high rates of arbuscular mycorrhizal fungi (AMF) association. However, the root traits that contribute to invasive success are less well known. Moreover, the combined roles of above-ground herbivory, AMF, and root traits in the invasion process are poorly understood. We conducted field surveys at 17 sites along a latitudinal gradient in China (22.77 degrees N to 42.48 degrees N) to investigate the relationships among above-ground herbivory, AMF colonization, and root traits for five pairs of closely related invasive and native Asteraceae plant species. We experimentally manipulated above-ground insect feeding for two of these pairs of plant species in a middle latitude (34.79 degrees N) common garden. We measured above-ground invertebrate abundance, leaf damage, AMF colonization, root morphological traits associated with nutrient uptake, and root soluble sugar concentrations. In the field survey, invasive plants had lower leaf damage and Hemiptera abundances plus higher AMF colonization, thinner roots with more surface area and higher concentrations of root soluble sugars than native plants. Leaf damage decreased with increasing latitude for native plants. In the common garden, invasive plants had lower leaf damage and Hemiptera abundances plus higher AMF and greater surface area of fine roots than native plants. Leaf damage and Hemiptera reduced AMF colonization via a phenotypic effect of reduced fine root soluble sugars. Synthesis: Our results indicate that low above-ground invertebrate herbivory on invasive plants contributes to their success directly by increasing their growth and indirectly via root soluble sugars that increase their AMF colonization. Invasive plants appear to benefit from greater root volume and surface area, but this did not vary with latitude or above-ground invertebrate herbivory. These results highlight the importance of considering above- and below-ground processes simultaneously to understand how they interact to determine plant invasion success.

Exploring the saline-adapted species and the mechanisms by which they have evolved in saline conditions would be a feasible way to utilize saline soils. Based on this approach, this study aimed to evaluate the seed germination and seedling responses of the five abundant Asteraceae species to salinity stress and determine the antioxidant and non-antioxidant defense strategies by which these species demonstrated variations in salinity tolerance. Milk thistle (Silybum marianum), blessed thistle (Cnicus benedictus), pot marigold (Calendula officinalis), safflower (Carthamus tinctorius), and cardoon (Cynara cardunculus) were subjected to 0 (control), 50, 100, 150, 200 and 250 Mm NaCl concentrations. Calendula officinalis (CO) showed the highest, Silybum marianum (SM) and Cnicus benedictus (CB) moderate, and Carthamus tinctorius (CT) followed by Cynara cardunculus (CC) the least inhibition of seed germination and seedling growth at all given salinity levels. Each species utilized different antioxidant mechanisms in response to salinity. Peroxidase (POX) was the major antioxidative enzyme in resistance species, CT and CC, while catalase and superoxide dismutase were more pronounced in moderate, SM and CB, and susceptible, CO, species, respectively. Besides, all species accumulate a considerable amount of proline in response to salinity, which was more evident in the 150 and 200 Mm NaCl concentrations. From the results, it can be concluded that CT and CC had superior saline-tolerance capacity compared to other species due to their longer seedling roots, higher POX activity, and proline accumulation associated with reduced cellular damage.

Selenium (Se) plays a crucial role in ameliorating the negative impact of abiotic stress. The present study was performed to elucidate the efficacy of soil treatment of Se in reducing salt-induced stress in Carthamus tinctorius L. In this study, three different levels of Na2SeO4 (0, 0.01, and 0.02 g kg- 1) and four levels of NaCl (0, 0.5, 1.5, and 2.5 g kg- 1) were applied. The findings revealed that while NaCl decreased seed germination parameters, growth characteristics, K+ content, relative water content (RWC), and photosynthetic pigments, it increased Na+ content, soluble carbohydrates, H2O2 content, and malondialdehyde (MDA) level. The application of Se showed a positive effect on seed germination and growth characteristics under salinity conditions, which is linked to alterations in anatomical, biochemical, and physiological factors. Anatomical studies showed that treatment with Se led to increased stem diameter, cortical parenchyma thickness, and pith diameter under salinity stress. However, variations in the thickness of the xylem and phloem did not reach statistical significance. The application of Se (0.02 g kg- 1) raised Na+ content (7.65%), K+ content (29.24%), RWC (15%), Chl a (17%), Chl b (21.73%), Chl a + b (16.9%), Car (4.22%), and soluble carbohydrates (11%) in plants subjected to NaCl (2.5 g kg- 1) stress. Furthermore, it decreased H2O2 (25.65%) and MDA (11.9%) in the shoots. The findings of the current study advocate the application of the Se-soil treating technique as an approach for salt stress mitigation in crops grown in saline conditions.