A return to the wild : root exudates and food security

Challenges to food security under conditions of global change are forcing us to increase global crop production. Focussing on belowground plant traits, especially root exudation, has great promise to meet this challenge. Root exudation is the release of a vast array of compounds into the soil. These exudates are involved in many biotic and abiotic interactions. Wild relatives of crops provide a large potential source of information and genetic material and have desirable traits that could be incorporated into modern breeding programs. However, root exudates are currently underexploited. Here, we highlight how the traits of root exudates of crop wild relatives could be used to improve agricultural output and reduce environmental impacts, particularly by decreasing our dependence on pesticides and fertilisers

Focus EMU, January 13, 1987

The drivers of global change, such as increasing drought and nutrient deposition, are affecting soils and their microbial communities in many different habitats, but how these factors interact remains unclear. Quercus ilex and Pinus sylvestris are two important tree species in Mediterranean montane areas that respond differently to drought, which may be associated with the soils in which they grow. We measured soil respiration and physiologically profiled microbial communities to test the impact of drought and subsequent recovery on soil function and diversity for these two species. We also tested whether the addition of nitrogen and phosphorus modified these effects. Drought was the stronger driver of changes to the soil communities, decreasing diversity (Shannon index), and evenness for both species and decreasing soil respiration for Q. ilex when N was added. Soil respiration for P. sylvestris during the drought period was positively affected by N addition but was not affected by water stress. P addition during the drought period did not affect soil respiration for either tree species but did interact with soil-water content to affect community evenness for P. sylvestris. The two species also differed following the recovery from drought. Soil respiration for Q. ilex recovered fully after the drought treatment ended but decreased for P. sylvestris, whereas the soil community was more resilient for P. sylvestris than Q. ilex. Nutrient addition did not affect respiration or community composition or diversity during the recovery period. Soil respiration was generally weakly positively correlated with soil diversity. We demonstrate that short-term water stress and nutrient addition can have variable effects on the soil communities associated with different tree species and that the compositions of the communities can become uncoupled from soil respiration. Overall, we show that drought may be a stronger driver of changes to soil communities than nitrogen or phosphorus deposition

Rhizodeposition under drought and consequences for soil communities and ecosystem resilience

Background: Rhizodeposition is the release of organic compounds from plant roots into soil. Positive relationships between rhizodeposition and soil microbial biomass are commonly observed. Rhizodeposition may be disrupted by increasing drought however the effects of water stress on this process are not sufficiently understood. - Scope: we aimed to provide a synthesis of the current knowledge of drought impacts on rhizodeposition. The current scarcity of well-defined studies hinders a quantitative meta-analysis, but we are able to identify the main effects of water stress on this process and how changes in the severity of drought may produce different responses. We then give an overview of the links between rhizodeposition and microbial communities, and describe how drought may disrupt these interactions. - Conclusions: overall, moderate drought appears to increase rhizodeposition per gram of plant, but under extreme drought rhizodeposition is more variable. Concurrent decreases in plant biomass may lessen the total amount of rhizodeposits entering the soil. Effects on rhizodeposition may be strongly species-dependant therefore impacts on soil communities may also vary, either driving subsequent changes or conferring resilience in the plant community. Advances in the study of rhizodeposition are needed to allow a deeper understanding of this plant-soil interaction and how it will respond to drought

Effects of past and current drought on the composition and diversity of soil microbial communities

Drought is well known to have strong effects on the composition and activity of soil microbial communities, and may be determined by drought history and drought duration, but the characterisation and prediction of these effects remains challenging. This is because soil microbial communities that have previously been exposed to drought may change less in response to subsequent drought events, due to the selection of drought-resistant taxa. We set up a 10-level drought experiment to test the effect of water stress on the composition and diversity of soil bacterial and fungal communities. We also investigated the effect of a previous long-term drought on communities in soils with different historical precipitation regimes. Saplings of the holm oak, Quercus ilex L., were included to assess the impact of plant presence on the effects of the drought treatment. The composition and diversity of the soil microbial communities were analysed using DNA amplicon sequencing of bacterial and fungal markers and the measurement of phospholipid fatty acids. The experimental drought affected the bacterial community much more than the fungal community, decreasing alpha diversity and proportion of total biomass, whereas fungal diversity tended to increase. The experimental drought altered the relative abundances of specific taxa of both bacteria and fungi, and in many cases these effects were modified by the presence of the plant and soil origin. Soils with a history of drought had higher overall bacterial alpha diversity at the end of the experimental drought, presumably because of adaptation of the bacterial community to drought conditions. However, some bacterial taxa (e.g. Chloroflexi) and fungal functional groups (plant pathogens and saprotrophic yeasts) decreased in abundance more in the pre-droughted soils. Our results suggest that soil communities will not necessarily be able to maintain the same functions during more extreme or more frequent future droughts, when functions are influenced by community composition. Drought is likely to continue to affect community composition, even in soils that are acclimated to it, tending to increase the proportion of fungi and reduce the proportion and diversity of bacteria

Assessment of the response of photosynthetic activity of Mediterranean evergreen oaks to enhanced drought stress and recovery by using PRI and R690/R630

Agraïments: Chao Zhang gratefully acknowledges the support from the Chinese Scholarship Council.The photochemical reflectance index (PRI) and red-edge region of the spectrum are known to be sensitive to plant physiological processes, and through measurement of these optical signals it is possible to use non-invasive remote sensing to monitor the plant photosynthetic status in response to environmental stresses such as drought. We conducted a greenhouse experiment using Quercus ilex, a Mediterranean evergreen oak species, to investigate the links between leaf-level PRI and the red-edge based reflectance ratio (R690/R630) with CO2 assimilation rates (A), and photochemical efficiency (FV/FM and Yield) in response to a gradient of mild to extreme drought treatments (nine progressively enhanced drought levels) and corresponding recovery. PRI and R690/R630 both decreased under enhanced drought stress, and had significant correlations with A, FV/FM and Yield. The differential values between recovery and drought treatments of PRI (DPRIrecovery) and R690/R630 (DR690/R630recovery) increased with the enhanced drought levels, and significantly correlated with the increases of DArecovery, DFV/FMrecovery and DYieldrecovery. We concluded that both PRI and R690/R630 were not only sensitive to enhanced drought stresses, but also highly sensitive to photosynthetic recovery. Our study makes important progress for remotely monitoring the effect of drought and recovery on photosynthetic regulation using the simple physiological indices of PRI and R690/R630

Generation of mice with a conditional Foxp2 null allele

Disruptions of the human FOXP2 gene cause problems with articulation of complex speech sounds, accompanied by impairment in many aspects of language ability. The FOXP2/Foxp2 transcription factor is highly similar in humans and mice, and shows a complex conserved expression pattern, with high levels in neuronal subpopulations of the cortex, striatum, thalamus, and cerebellum. In the present study we generated mice in which loxP sites flank exons 12–14 of Foxp2; these exons encode the DNA-binding motif, a key functional domain. We demonstrate that early global Cre-mediated recombination yields a null allele, as shown by loss of the loxP-flanked exons at the RNA level and an absence of Foxp2 protein. Homozygous null mice display severe motor impairment, cerebellar abnormalities and early postnatal lethality, consistent with other Foxp2 mutants. When crossed to transgenic lines expressing Cre protein in a spatially and/or temporally controlled manner, these conditional mice will provide new insights into the contributions of Foxp2 to distinct neural circuits, and allow dissection of roles during development and in the mature brain. genesis 45:440–446, 2007. Published 2007 Wiley-Liss, Inc

Quan les fonts s’assequen. Situació dramàtica de les fonts de la Serralada Litoral davant la crisi climàtica

Deu anys després de l’inici del Projecte Fonts s’han visitat 31 fonts de la Serralada Litoral ja estudiades fa una dècada per tal de comparar els seus cabals antics amb els actuals. A totes les 31 fonts brollava aigua amb més o menys cabal el 2013. A data d’avui, 14 d’aquestes fonts (45,2%) estan totalment eixutes i a la resta s’han mesurat uns cabals molt inferiors als de fa deu anys. El 2013 el sumatori dels cabals de les 31 fonts era de 1.891,6 ml/s, mentre que el 2023 és només de 152,5 ml/s, la qual cosa representa una pèrdua de 1.739,1 ml/s, és a dir el 91,9% del cabal d’aigua. A la majoria de fonts on s’ha perdut el flux d’aigua, s’han perdut també les comunitats de briòfits i en conseqüència tota la microbiota associada. Atès que moltes d’aquestes comunitats són pràcticament encara desconegudes, la pèrdua podria ser especialment rellevant en uns hàbitats que han estat considerats punts calents de biodiversitat.Ten years after the start of the Projecte Fonts, 31 springs from the Serralada Litoral, previously studied a decade ago, have been visited in order to compare their current water discharge with those from ten years go. All 31 springs presented water discharge in 2013. Today, 14 of these springs (45.2%) are completely dry and the rest have discharge rates that are much lower than ten years ago. In 2013 the sum of the water discharge of the 31 springs was 1,891.6 ml/s, while in 2023 it is only 152.5 ml/s, which represents a loss of 1,739.1 ml/s, a reduction of 91.9% of the water. In most springs where water flow has been completely lost, bryophyte communities have also been lost and, consequently, all associated microbiota. Given that many of these communities are still largely unknown, the loss of biodiversity could be particularly relevant in habitats that have been considered biodiversity hotspots.info:eu-repo/semantics/publishedVersio

Were Fertile Crescent crop progenitors higher yielding than other wild species that were never domesticated?

During the origin of agriculture in the Fertile Crescent, the broad spectrum of wild plant species exploited by hunter-gatherers narrowed dramatically. The mechanisms responsible for this specialization and the associated domestication of plants are intensely debated. We investigated why some species were domesticated rather than others, and which traits they shared. We tested whether the progenitors of cereal and pulse crops, grown individually, produced a higher yield and less chaff than other wild grasses and legumes, thereby maximizing the return per seed planted and minimizing processing time. We compared harvest traits of species originating from the Fertile Crescent, including those for which there is archaeological evidence of deliberate collection. Unexpectedly, wild crop progenitors in both families had neither higher grain yield nor, in grasses, less chaff, although they did have larger seeds. Moreover, small-seeded grasses actually returned a higher yield relative to the mass of seeds sown. However, cereal progenitors had threefold fewer seeds per plant, representing a major difference in how seeds are packaged on plants. These data suggest that there was no intrinsic yield advantage to adopting large-seeded progenitor species as crops. Explaining why Neolithic agriculture was founded on these species, therefore, remains an important unresolved challenge

Efecte de les variables ambientals i hidrològiques sobre la riquesa i distribució dels briòfits fontinals a la Catalunya oriental

Els briòfits tenen uns trets funcionals que fan d'ells uns dels indicadors més sensibles als canvis ambientals. En aquest treball vam estudiar si la riquesa d'espècies de briòfits i llurs distribucions es podien predir fent servir variables macroecològiques (p. ex., el clima, l'altitud i la conductivitat i el pH de l'aigua) a partir del mostreig de les comunitats de briòfits de 198 fonts distribuïdes entre la Serralada Litoral Central, el massissos del Montseny-Guilleries, el Lluçanès i la Garrotxa. Fent servir regressions lineals, vam relacionar les variables ambientals amb la riquesa d'espècies per font. Seguidament, mitjançant un anàlisi de components principals (ACP), vam agrupar les variables ambientals en tres eixos descriptius de la variabilitat ambiental de les fonts. Fent servir les variables ambientals i els tres eixos extrets de la ACP, vam comprovar la influència d'aquestes sobre la distribució d'espècies fent servir anàlisis de la variància (ANOVA). Els nostres resultats suggereixen que la riquesa d'espècies està positivament relacionada amb la precipitació anual, el pH de l'aigua de la font i l'altitud a la que es troba la surgència. Tanmateix, la variància explicada pel model va ser força baixa (Bryophytes have biological traits that make them some of the most sensitive indicators of environmental change. Springs have a significant presence of bryophytes and hence they are ideal habitats for studying their relationship with the environment. We tested whether bryophyte species richness and distribution can be predicted with macroecological variables (i.e., climate, altitude, water pH and conductivity) sampling bryophytes from 198 springs distributed along montane regions in NE Iberian Peninsula. Regressions were used to relate species richness with selected environmental variables. A PCA analysis was performed to reduce the environmental variables to three principal coordinates. We tested the influence of environmental variables and PCA axis on species distribution using ANOVAs. Our results suggest that species richness is related to mean annual precipitation, water pH and altitude. However, total variance explained by the model is low

Thirsty tree roots exude more carbon

Root exudation is an important input of carbon into soils and affects plant and soil communities, but little is known about the effect of climatic factors such as drought on exudation, and its ability to recover. We studied the impact of increasing drought on root exudation and its subsequent recovery in the Mediterranean tree species Quercus ilex L. in a greenhouse study by measuring the amount of total organic carbon in exudates. The amount of exudation per unit root area increased with drought duration and was 21% higher under the most extreme drought scenario compared with the non-droughted control. The amount of root exudation did not differ between the treatments following 6 weeks of re-watering, indicating a strong capacity for recovery in this species. We concluded that drought could affect the amount of root exudation, which could in turn have a large impact on microbial activity in the rhizosphere, and alter these microbial communities, at least in the short term. This tree species may be able to return to normal levels of root exudation after a drought event, but long-term exudate-mediated impacts on Mediterranean forest soils may be an unforeseen effect of drought