Food security is threatened by co-occurring stresses (e.g. salinity and drought) under global climate change. To circumvent major impacts on food production, the vulnerabilities and tolerances to these threats need to be characterized. Traditionally, the tolerance of crops is evaluated in highly controlled small-scale experiments involving only a limited number of crop types. To increase our understanding in actual agricultural tolerances, plant functioning, as observed by functional traits, need to be performed in real-life scenarios for as many crops as possible. Remote sensing is presently the only tool capable of monitoring such plant functional traits simultaneously over large areas.

The aim of this research therefore is to evaluate the crop tolerances to combined drought and salinity stress across various plant functions in real-life conditions. We evaluated drought and salinity tolerance impacts on different types of crops across the entire US continent, using five traits representative of different plant functions. Given crop tolerance highly depended on the moments, we evaluated the dominant stress and the onset among individual and combined effects of drought and salinity for five traits from March to October.

We found strong interaction effects between stress and time using two-way ANOVAs. In general, crops were more sensitive to combined drought and salinity, although they differ significantly between species and moments. Of the individual traits, LAI was triggered first by stresses, followed by FAPAR and FVC, and Cab and Cw were the last to respond to stresses. This implies that plants reduce primary production before reducing water content.

Our study provides a way of evaluating the tolerance of diverse crops to co-occurrence stresses both separately and in combination. Through applications to other vegetation types and stresses, our approach creates a quantitative backbone to inform sustainable food production.

How to cite: Wen, W., Timmermans, J., Chen, Q., and van Bodegom, P. M.: Diverse responses of multiple crops to drought and salinity stress , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1175, https://doi.org/10.5194/egusphere-egu23-1175, 2023.

Agricultural lands provide a near-term opportunity to address climate change, food, and water security challenges. Addressing these complex challenges will require the integration of empirical data on the natural variation of vegetation traits with computational approaches that can integrate this empirical information toward an understanding of canopy-scale impacts. The relationships between leaf chlorophyll content, leaf optical properties, and biochemical photosynthetic capacity were measured in a collection of soybean (Glycine max) accessions showing large variations in leaf chlorophyll content (Chl). These relationships were integrated into a biophysical model of canopy-scale photosynthesis to simulate the within-canopy light environment, carbon dioxide assimilation and water use. Simulations were conducted for each accession to identify possible opportunities for improving canopy photosynthesis through foliar chlorophyll modification. These simulations demonstrate that canopy photosynthesis may not increase as Chl is reduced due to increases in leaf reflectance and nonoptimal distribution of canopy nitrogen. However, similar rates of canopy photosynthesis can be maintained with a 9% savings in leaf nitrogen resulting from decreased Chl. Additionally, analysis of these simulations indicates that the inability of Chl reductions to increase photosynthesis arises primarily from the connection between Chl and leaf reflectance and secondarily from the mismatch between the vertical distribution of leaf nitrogen and the light absorption profile. These simulations motivated the use of numerical optimization to quantify the extent to which low Chl mutations can be used to improve canopy performance by adapting the distribution of the “saved” nitrogen within the canopy to take greater advantage of the more deeply penetrating light. We conclude with a discussion of the impact of the re-distribution of nitrogen vertically through the canopy to improve photosynthesis and canopy water use.

How to cite: Drewry, D.: Simulating the field-scale potential of natural variation in soybean leaf optical properties on carbon assimilation and water use, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4045, https://doi.org/10.5194/egusphere-egu23-4045, 2023.

Efficient and safe water transport in plants depends on specific wood anatomical structures. Comparing the hydraulic vulnerability among tree species and individuals can be biased by differences in the sampling procedure resulting in unjustified conclusions. In fact, water-transporting conduits of the xylem widen from the tree-tip toward the base potentially influencing xylem vulnerability to embolism formation.

The resistance to cavitation and embolism formation (hydraulic vulnerability curves) was empirically tested at different positions from the tree-tip to the trunk base in a mature Norway spruce and a silver fir tree. Anatomical analyses (conduit diameter, pit traits) were performed on the same material used for hydraulic measurements.

Substantial intra-plant variation in xylem anatomy and vulnerability to embolism was observed in both species scaling with the distance from the apex. The P50 values (i.e. the water potential resulting in 50% loss of hydraulic conductivity) were about 3 MPa more negative at the tip than at the trunk base. Tracheid diameters and pit dimensions increased from the apex downwards, confirming the tip-to-base conduit widening. The highest variability of both anatomical and physiological traits was observed within the first 3 m from the apex. We propose a method for the prediction of drought vulnerability based on hydraulically weighed conduit diameter distribution.

A clear pattern of anatomical traits’ variation along the longitudinal axes of the tree was observed, likely playing a role in the increase of vulnerability to embolism. In comparative studies, we thus recommend to standardize the sampling of material according to the distance from the apex.

How to cite: Savi, T., Zambonini, D., Zagudaeva, K., Rosner, S., and Petit, G.: From tree-tip to trunk-base: interplay of resistance to embolism formation and wood anatomy in two conifers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5633, https://doi.org/10.5194/egusphere-egu23-5633, 2023.

The increasing occurrence and intensity of climate extremes, such as droughts, threaten forests and the many services they provide to society. Mixed-species forests are promoted as a forest management strategy for climate change adaptation, but whether they are generally more resistant to drought than monospecific forests remains unresolved. Particularly, the trait-based mechanisms driving tree resistance to drought remain elusive, making it difficult to predict which functional identities of species best improve tree growth and decrease tree physiological water stress under drought.

Here, we investigated tree growth and physiological stress responses (i.e. increase in wood carbon isotopic ratio; δ¹³C) to changes in climate-induced water availability (wet-to-dry years) along gradients in neighbourhood tree species richness and drought-tolerance traits. For this purpose, we sampled tree cores in a large-scale forest biodiversity experiment (BEF-China experiment). We tested the overarching hypothesis that neighbourhood species richness increases growth and decreases δ¹³C. We further hypothesized that the abiotic (i.e. climatic conditions) and the biotic context modulate these biodiversity-ecosystem functioning relationships. We characterized the biotic context using drought-tolerance traits of focal trees and their neighbours. These traits are related to cavitation resistance vs. resource acquisition and stomatal control.

We found that tree growth increased with neighbourhood species richness. However, we did not observe a universal relief of water stress in species-rich neighbourhoods, nor an increase in the strength of the relationship between richness and growth and between richness and δ¹³C from wet-to-dry years. Instead, these relationships depended on both the traits of the focal trees and their neighbours. At either end of the resistance-acquisition and stomatal control trait gradient, species responded in opposing directions during drought and non-drought years.

We report that the biotic context can determine the nature of biodiversity-ecosystem functioning relationships in experimental tree communities. We derive two key conclusions: (1) drought-tolerance traits of focal trees and their neighbours can explain divergent tree responses to drought and diversity, and (2) contrasting, trait-driven responses of tree species to wet vs dry climatic conditions can promote forest community stability. Mixing tree species with a range of drought-tolerance traits may therefore increase forest productivity and stability but may not universally relieve drought stress.

How to cite: Schnabel, F., Barry, K. E., Eckhardt, S., Guillemot, J., Geilmann, H., Kahl, A., Moossen, H., Bauhus, J., and Wirth, C.: Species richness and drought-tolerance traits explain opposing tree growth and δ13C responses to climate extremes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6187, https://doi.org/10.5194/egusphere-egu23-6187, 2023.

Breeding drought resilient crops requires understanding the mechanisms underlying plant physiological responses to different drought patterns and how these vary within species.Two main plant water use strategies are distinguished in the literature, referred to as “risk – taking” (anisohydric) and “conserving” (isohydric). Under well-watered conditions, risk takers exhibit a higher transpiration rate (TR) associated with a greater CO₂ assimilation rate, and hence, greater dry matter production than conserving plants which have a tighter stomatal control. Depending on the root traits the transpiration-limiting soil moisture level (θ_crit) can differ between plants with similar shoot traits. A high θ_crit (e.g. due to shallow roots) entails early stomata closure. This study aimed at examining the drought response of four high-yielding European spring barley cultivars considered to exhibit different response behavior.

We collected detailed plant physiological data with a high- throughput functional phenotyping platform (Plantarray®, Plant-Ditech) and analyzed final yield parameters. Around flowering cv. Chanelle (CHAN), RGT Planet (RGT), Formula (FORM), and Baroness (BAR) were exposed to 12 days of drought. Based on higher TR, higher biomass and grain yield under well-watered conditions and the faster TR reduction below θ_crit ,CHAN ranked as very risk taking and RGT as risk taking in contrast to conserving FORM and very conserving BAR.

Drought effects on final yield are closely linked to the plants recovery potential, i.e. the ability to increase TR to control plant levels upon re-irrigation. The highest yielding cultivar under ample water supply, CHAN, showed a significantly impaired recovery potential and suffered notable yield penalties under drought (24%). The very conserving response behavior of BAR resulted in good recovery, minimal yield loss (-2% yield) and a final grain yield that was almost similar to very risk taking CHAN (Δ 5g/pot). FORM produced the lowest yields under control and stress conditions yet suffered no drought induced yield penalties, probably due to a better adapted root system. The lower θ_crit of FORM delayed stomata closure and the breakdown of assimilation. FORM and RGT had similar recovery rates.

RGT produced the second highest yield under well-watered conditions and drought did not cause any yield losses. Under ample water supply, RGT behaved like a risk taker, whereby the high TR allowed it to be more productive than the conserving cultivars. RGT switched to a more conserving behavior under drought where it only gradually (same slope as FORM) decreased TR below θ_crit and was thereby more productive than very risk taking CHAN. This rather dynamic water use behavior made RGT the best performing cultivar in the here examined drought scenario.

A higher number of seeds per spike (along with reduced kernel size) likely contributed to the yield stability observed under drought in FORM and RGT the exact physiological mechanisms of which still require more investigation. Prospective studies will examine different drought patterns and durations and implement the gained knowledge into crop simulation models for upscaling.

Keywords: water-response behavior, isohydric; anisohydric; spring barley, drought

How to cite: Appiah, M., Abdulai, I., Dewi, E. S., Daszkowska-Golec, A., Bracho-Mujica, G., Schulman, A., Moshelion, M., and Rötter, R. P.: Drought response behavior of risk-taking and conserving spring barley cultivars, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7999, https://doi.org/10.5194/egusphere-egu23-7999, 2023.

The presence of unique environmental factors such as ionizing radiation (IR) in Space may be a major hindrance to the survival of terrestrial organisms. Therefore, understanding the impact of Space radiation on organisms is an essential part of exploration research to successfully inhabit Moon and Mars.

Given the pivotal role of plants in sustainable closed artificial ecosystems in Space (i.e. Bioregenerative Life Support Systems) as food producers and bio-regenerators of environmental resources such as oxygen and water, and, plant resistance to IR is undoubtedly one of the first trait to consider. Indeed, IR may influence plants growth and development, potentially affecting their bioregenerative performance, jeopardizing astronaut survival and in turn the success of future Space missions. Notwithstanding, available information on plants' responses to IR remain unclear, and intrinsic IR and plant factors (e.g., type of radiation, dose, plant species, cultivar, and developmental stage at the time of irradiation) interactions must be considered.

The purpose of this study was to test the radio resistance of the Salanova® lettuce (Lactuca sativa L. var. capitata) to different doses of high-LET (Linear Energy Transfer) radiation, in terms of morpho-anatomical and nutritional traits. At the GSI Helmholtzzentrum für Schwerionenforschung GmbH, dry seeds were exposed to increasing doses (0-control, 0.3, 1, 10, 20, and 25 Gy) of iron ions (56^Fe) (one of the most damaging ions in the galactic cosmic ray spectrum). Following irradiation, plants were grown in a growth chamber under controlled light, temperature, and relative humidity conditions.

Seed germination percentage, as well as plant growth and leaf photosynthesis performances were monitored during cultivation.

Morpho-biometric parameters such as plant total leaf area, number of leaves, and fresh and dry biomass were quantified at harvest. Leaf functional anatomical traits (e.g., lamina thickness, stomatal frequency and size, vein density) were also analyzed using light and epifluorescence microscopy and digital image analysis. Finally, to assess the phytochemical and nutritional profile, the antioxidant capacity, chlorophylls, carotenoid, and mineral composition content were determined.

Results showed that responses of Salanova lettuce from irradiated seeds changed depending on the IR dose delivered, with the occurrence of both hormetic and detrimental outcomes, as well as possible plant radioprotective strategies. This information will be helpful to unveil the mechanisms behind plant radiotolerance and to define the shielding requirements for Space cultivation facilities.

Part of the results presented here is based on the experiment Bio_08_DeMicco, which was performed at the SIS18 at the GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany) in the frame of FAIR Phase-0.

How to cite: De Francesco, S., Amitrano, C., Tinganelli, W., Durante, M., De Pascale, S., Arena, C., and De Micco, V.: Morpho-anatomical and biochemical modifications in Lactuca sativa L. plants in response to increasing doses of High-LET ionizing radiation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8395, https://doi.org/10.5194/egusphere-egu23-8395, 2023.

Although evidence of the incidence of foliar water uptake has previously been documented in white spruce (Picea glauca), its eco-physiological importance remains unclear. Our aim was to evaluate the ecological significance of functional differences in foliar water uptake between populations relative to their climate of origin, foliar anatomy, and aquaporin expression.

To investigate needle radial anatomies, micrographs were made using new growth needles collected from 11 provenances growing in a range-wide common garden experiment near Athabasca Alberta. Correlations were then performed to determine relationships between the anatomies and climatic parameters of origin. A foliar water uptake experiment was then conducted on twigs with new growth needles from 6 representative provenances, 3 pairs, each from a different climatic ecozone to best capture a gradient of differences in latitude and marked differences in climate of origin and needle anatomy. The experiment was run using two initial desiccation levels on the 3 ecozones selected—mild, and severe—and mass measurements and tissue samples for RT-qPCR of PIP aquaporins were taken before dehydration, and at t=0, 30, 60, and 240 minutes.

Provenances with thinner Casparian strips and hypodermis layers lost more water during needle dehydration but were also able to take up water faster when wet. Dry climate, Boreal Plains provenances, were anatomically maladapted to drought but had a greater water influx than the others over the first 30 minutes of wetting, which may be explained by their greater aquaporin expression levels during uptake. Expression rates of PIP aquaporins 1;1, and 2;2 were strongly positively correlated with RWC and 1;2 was negatively correlated with the hypodermis thickness.

We conclude that population level differences in foliar water uptake are facilitated by needle anatomy and mediated by aquaporin expression. Our results suggest that there are inherent trade-offs between productivity maintenance in cold climates, drought tolerance, and foliar water uptake. Colder climate populations are anatomically maladapted to drought, but some may be able to compensate with foliar water uptake.

How to cite: Fleurial, K. G., Sebastián Azcona, J., Hamann, A., and Zwiazek, J. J.: Threading the white spruce needle: hydraulic foliar adaptive traits stitch a story of diffusion trade-offs between growth maintenance, drought resistance, and needle water uptake, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13695, https://doi.org/10.5194/egusphere-egu23-13695, 2023.

Extraordinary changes in alpine fire regimes have been often associated with heat waves, which are generally regarded as an indication of a changing climate that will lead to new fire regimes in the Alps. Fine roots function of absorbing water and nutrients is crucial to plant survival and their traits such as biomass, length, specific root length, production, death, and decomposition can inform how trees interact with their environments and provide ecological functions in response to exogenous stresses. After an unusual, late-fall wildfire in a European beech (Fagus sylvatica L.) forest in the pre-Alps of northern Italy, the response of fine roots (< 2 mm diameter) was analysed and appeared more evident when fine roots were further subdivided by diameter size and soil depth. The finest roots (0‒0.3 mm diameter) were generally the most responsive to fire, with the effect more pronounced at the shallowest soil depth. While roots 0.3‒1 mm in diameter had their length and biomass at the shallowest soil depth reduced by fire, fire stimulated more length and biomass at the deepest soil depth compared to the control. Fire elevated the total length of dead roots and their biomass immediately and this result persisted through the first spring, after which control and fire-impacted trees had similar fine root turnover. Our results add to the paucity of data concerning fire impacts on beech roots in a natural condition and provide the basis for understanding fine-root morphological traits approach to assess plant species vulnerability and resilience to unusual fire occurrence due to climate changes. Changes in disturbance regimes might be most realized by distribution of the finest of fine roots at differing soil depths, and the dynamics of these roots may provide the most resilience to disturbance.

How to cite: Montagnoli, A., Terzaghi, M., Miali, A., Chiatante, D., and Dumroese, K.: Fine-root morphological traits may improve understanding of the vulnerability of Fagus sylvatica natural forests to late-fall unusual wildfire, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17297, https://doi.org/10.5194/egusphere-egu23-17297, 2023.

In the current scenario of decreasing in precipitation and water resources, and increasing in temperature,   it is pivotal to define multiple strategies to cope with the negative consequences on the crop production and food security. Hazelnut (Corylus avellana L.) is an important nut tree crop grown in several countries all over the world and mainly in the Mediterranean Basin area. Among the producer countries Italy is the second main worldwide producer, soon after Turkey. Despite the long-lasting and traditional cultivation of hazelnut in the hilly areas and a recent wider spread of its orchards to newly cultivated fertile plains, hazelnut is well known as a very sensitive species to both water stress and high temperatures. The main aim of this study was to evaluate growth performances and morpho-physiological adaptive responses to prolonged water stress in potted young hazelnut plants. Secondarily, the effect of biostimulant treatments in mitigating the effects of water and heat stresses were evaluated. The research was conducted on one-year-old cultivar micro propagated plants of cv “Tonda di Giffoni” grown in a cold polycarbonate greenhouse at the Department of Agricultural Sciences of the University of Naples “Federico II” during two consecutive growing seasons. Three irrigation levels (i.e. 100, 80, and 60% of the daily water requirement) were applied in combination with two different biostimulant treatments. In particular, they consisted in the application near the roots of protein hydrolysate or mycorrhizae inoculation. The first one was applied every two weeks with a dosage of 2.5 ml/l according to the chemical characteristics of the product, during the whole growing season; instead, the second one was applied with a single-dose of 15 g per plant at the beginning of each growing season. During the two seasons, growth rate (i.e. basal diameter, branch length, leaf number, leaf area, and buds), eco-physiological behaviour (i.e. gas exchanges measurements, Chlorophyll a fluorescence emission, SPAD index, and leaf water potential), and leaf functional traits were investigated. Results   showed that the use of biostimulant and mycorrhizae positively influenced physiological behaviour and growth of plants by counteracting deficit irrigation stress effects. In conclusion, our study demonstrate how these type of treatments help to improve the quality of plants.

How to cite: Vanacore, L., Modarelli, G. C., El-Nakhel, C., Pannico, A., Rouphael, Y., and Cirillo, C.: Biostimulant applications to mitigate multiple summer stress effects on potted Corylus avellana L. young plants, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9556, https://doi.org/10.5194/egusphere-egu23-9556, 2023.