Michal Gruntman’s research while affiliated with Tel Aviv University and other places

Plant chemical composition is a trait gaining increasing importance in plant ecology. However, there is limited research on the patterns and drivers of its variation among different plant functional groups and bioclimatic regions. We conducted an analysis of ionomes utilising X‐ray fluorescence on 83 plant species from four distinct functional groups (grasses, legumes, forbs and woody species); we marked plots across 15 sites located in both the desert and Mediterranean bioclimatic regions. The primary factors influencing variations in ionomes are predominantly attributed to bioclimatic factors rather than soil composition. Across all functional groups, plants from the Mediterranean region are characterised by greater association with calcium, whereas desert plants exhibit a higher affinity for strontium (Sr), suggesting its potential role in drought tolerance. Among functional groups, grasses uniquely exhibit distinct ionomic features, primarily due to their higher silicon (Si) concentrations. Plant species' affinities for certain elements and their interactions are likely driven by physiological constraints, whereas variations within a functional group are mostly driven by environmental conditions. We conclude that interactions among elements form physiological phenotypes shaped by natural selection under large‐scale environmental variability, making plant ionome composition an important plant functional trait.

In urban environments, attention has traditionally been paid to public open spaces. However, private open spaces constitute a significant percentage of the urban area and can thus play a significant role in enhancing biological diversity and facilitating direct interactions between humans and nature within urban settings. According to the 2018 European Union report, 46% of homeowners across Europe live in apartment buildings and yet, most studies that examine the effect of private open spaces on biodiversity focus primarily on yards of single-family housing. The objective of this study is to examine the biodiversity potential offered by shared residential yards focusing exclusively on wild plant species, with the aim of offering planning guidelines that address both the management practices of these lot spaces and their spatial arrangement and qualities. The study was conducted in the city of Givatayim, Israel, in shared residential yards. The basic units (lots and buildings on them) in the city were delineated using a novel approach through a separate characterization of lot sizes and building types, as well as their combination. This process resulted in typologies that cover all residential fabric in the city, allowing systematic sampling. In the spring of 2022, plant surveys were conducted in 56 randomly chosen yards. In these lots, potential open area was measured, and the level of non-maintenance (neglection) was also rated. 74 species of wild plants were found, representing a quarter of all wild plant species in the city. Our results show the combined positive effect of available open space and levels of non-maintenance in these yards on the richness and diversity of wild species. This study highlights the substantial area occupied by residential yards in the city and its role in maintaining biodiversity in urban environments. This study indicates the importance of considering these aspects in architectural and management policies in cities.

Trichomes play a key role in both heavy metal tolerance and herbivory defense, and both stressors have been shown to induce increased trichome density. However, the combined effect of these stressors on trichome density in general, and specifically on metal-hyperaccumulating plants, has yet to be examined. The aim of this study was to test the effect of cadmium availability and herbivory on leaf trichome density and herbivore deterrence in the metal hyperaccumulator Helianthus annuus. To test this, H. Annuus plants were grown in control pots or pots inoculated with 10 mg/kg cadmium and were subjected to either no herbivory or simulated herbivory using mechanical damage and foliar jasmonic acid application. Herbivore deterrence was tested in a feeding assay using Spodoptera littoralis caterpillars. Interestingly, while the trichome density of H. annuus increased by 79% or 53.5% under high cadmium availability or simulated herbivory, respectively, it decreased by 26% when the stressors were combined. Furthermore, regardless of cadmium availability, simulated herbivory induced a 40% increase in deterrence of S. littoralis. These findings suggest that the combination of metal availability and herbivory might present excessive stress to hyperaccumulators. Moreover, they suggest that the risk of metal bioaccumulation in phytoremediation can be reduced by simulated herbivory.

Belowground plant competition has been shown to induce varying responses, from increases to decreases in root biomass allocation or in directional root placement. Such inconsistencies could result from the fact that root allocation and directional growth were seldom studied together, even though they might represent different strategies. Moreover, variations in belowground responses might be due to different size hierarchies between plants, but this hypothesis has not been studied previously. In a greenhouse rhizobox experiment, we examined the way both root allocation and directional root placement of Pisum sativum are affected by the size and density of Festuca glauca neighbours, and by nutrient distribution. We found that root allocation of P. sativum increased with the density and size of F. glauca. By contrast, directional root placement was unaffected by neighbour size and increased either towards or away from neighbours when nutrients were patchily or uniformly distributed, respectively. These results demonstrate that directional root placement under competition is contingent on the distribution of soil resources. Interestingly, our results suggest that root allocation and directional placement might be uncoupled strategies that simultaneously provide stress tolerance and spatial responsiveness to neighbours, thus highlighting the importance of measuring both when studying belowground plant competition.

Stress experienced during development in organisms with bilateral structures could result in developmental instability, which is expressed as subtle non‐directional deviations from perfect symmetry, known as fluctuating asymmetry (FA). As such, FA has been proposed, and extensively used, as a trait indicating stress for many organisms with bilateral structures and many types of stress. However, while this concept may apply to animals, the evidence for plants' main vegetative structures, that is, leaves, remains equivocal, and a comprehensive synthesis on this topic is still missing. We designed observational field and controlled greenhouse studies, combining different growth and leaf forms across multiple stress gradients, comprising 21 species and 80 populations. We measured FA as the difference between the left and right area of the leaf, an approach that accommodates diverse leaf forms. We used high‐precision, blind, single‐person measurements and tested for other forms of symmetry and the effect of leaf size. We further complemented our study with a systematic literature review of FA in plant leaves, compiling 51 studies comprising 72 species, 23 stress types and 131 unique entries (species × stress type). We consistently found no effect of stress on leaf FA in any of the studied species in both our field and experimental gradients. In the systematic literature review, only 39% of the unique entries showed the expected increase in FA with stress, 53% showed no effect, 9% showed an opposite trend of a decrease in FA with stress and 1% showed a unimodal relationship. Importantly, only 40% of all entries fulfilled the crucial step of controlling for a high‐precision measurement, and of these 49% reported the expected increase in FA with stress. Both the results of our observational and experimental approaches and the systematic literature review failed to support a clear relationship between stress and FA in plant leaves. These results clearly show that FA in plant leaves cannot be used as a reliable trait indicating stress during development. Read the free Plain Language Summary for this article on the Journal blog.

The success of invasive species is often attributed to rapid post-introduction evolution, due to novel selection pressures at the introduced range. However, evolutionary shifts in invasion-promoting traits can also take place within the introduced range over time. Here, we first present a review of the proposed hypotheses regarding the selection pressures and trait divergence along gradients of invasion history and the studies that examined them. In addition, we present the results of a meta-analysis aimed to provide a more general overview of current knowledge on trait evolution with time since introduction. Invasion-promoting traits, including growth, competitive ability and dispersal ability, were proposed to decline in more established populations with a long invasion history due to the attenuation of selection pressures, such as enemy release or interspecific competition, while herbivore defence was suggested to increase. Our meta-analysis results reveal a general indication for the evolution of invasive plants with residence time for most of the studied traits. However, this divergence did not have a consistent direction in most traits, except for growth, which, in contrast with our prediction, increased with residence time. The lack of empirical support for the predicted change in most of the studied traits over time suggests trait evolution might be affected by other context-dependent factors such as climatic gradients along invasion routes. Similarly, the increased allocation to size in older and more established populations may be driven by increased conspecific competition pressure experienced in these populations. The general temporal effect found in our meta-analysis stresses the need to consider population age when comparing attributes of invasive plants between native and invasive ranges. Moreover, the increased size of invasive plants in older populations, suggests that the dominance of these plants might not attenuate with time since introduction, thus highlighting the need to further explore the long-term dynamics between invasive plants and their recipient native communities.

Accessible urban nature is a key component of creating sustainable urban communities and promoting human health and well-being. To balance the economic, social, and environmental dimensions of sustainable development, the United Nations adopted several sustainable developmental goals (SDGs), such as SDG 11 for sustainable cities and communities, which aims to improve urban planning and management, including equitable access to urban nature. However, more information is still needed regarding how planners and managers can promote urban nature visitation and equitable access during health and environmental crises, such as the COVID-19 pandemic. The purpose of this study was to examine trends in urban nature visitation during the pandemic and then to determine if the effect of the pandemic on the frequency of urban nature site visitation varied by distance to home, using an innovative approach of analyzing both publicly available large-scale mobility data and a web-based survey of urban residents of Tel Aviv-Yafo, Israel. The mobility data results showed that there was a negative mean % difference in park visits compared to baseline during the first and third lockdowns, but an increase compared to baseline between lockdowns and even during the second lockdown. This suggests that urban residents had greater need to reconnect with urban nature during and after periods of intense stress. In addition, the survey results showed an increasing negative effect of distance on urban nature site visitation during the pandemic, specifically for urban nature sites located more than 1 km from home. Altogether, the mobility data and survey results suggest that people who lived within 1 km of their preferred urban nature site had disproportionate access to the benefits of urban nature during and after lockdowns than others. To effectively make social and ecological transitions toward urban sustainability, it is vital that cities promote urban nature accessibility during current and future environmental and health crises. Cities should collaborate with diverse stakeholders to create/maintain accessible urban nature sites nearby all sociodemographic groups, provide sustainability education and training to convey the benefits of urban nature, and pursue participatory solutions for understanding urban nature needs and preferences. In this manner, it will be possible to address the growing influence of proximity/travel distance and additional factors that affect urban nature visitation and ultimately, human health and urban sustainability.

Can you think of places in the city where you enjoy nature? Urban nature may include parks and even backyards! Urban nature provides habitats for plants and animals and helps to promote human health. Our study examined how visiting urban nature sites may have changed during the COVID-19 pandemic, and which factors played a role in this change. We used map-based data and an online survey to answer our question for the city of Tel Aviv-Yafo in Israel. We found that visits to urban nature sites decreased for most of our participants. Participants who increased their visits to urban nature sites indicated that the sites helped their physical and mental health, were easy to get to, and were well maintained. We recommend that communities continue managing urban nature sites to improve accessibility and promote human health—both in normal times and in case of future pandemics.