Root exudation in tomatoes under drought and pathogen attack
Drought increased the exudation of carbon and nitrogen per unit of root area, however, due to the reduction in plant and root biomass caused by drought, the total exudation per plant remained similar between control and water-limited plants. Simulated pathogen attack reduced the carbon-to-nitrogen ratio of exudates and increased the total exudation of nitrogen. A collaboration with the Research Unit Environmental Simulation (Helmholtz Munich).
Preece et al., (2023), Plant and Soil, doi.org/10.1007/s11104-023-06421-9
Competition traits in crop progenitors
Cereal crop progenitors in our greenhouse study had greater germination success, germinated more quickly and had greater aboveground biomass when grown in competition with other species, and seed size was positively correlated with a number of traits. In mixtures, the positive effect of seed mass on germination success and speed of germination was even more beneficial for crop progenitors than for other wild species, suggesting greater fitness. Competition within plant communities surrounding human settlements may have benefited progenitor species, favouring their success as crops.
Preece et al., (2021), Ecology and Evolution, 11(7), 3300-3312.
The origins of agriculture
This synthesis paper brings together data from a number of our previous experiments, finding that: (1) Southwest Asian crop progenitors did not have greater total seed yield than other wild species; (2) seed enlargement in vegetable crops due to domestication was comparable with that of grain crops; (3) crop progenitors germinate faster and have larger seedlings than other wild species. Ecological processes, and unintended selection due to competition between growing plants within anthropogenic environments, may have played a larger role in the emergence of agriculture than previously supposed.
Jones et al., (2021), Journal of Archaeological Science, 125, 105290.
Root exudates and food security
Achieving food security under conditions of global change requires us to re-think global food production. A new focus on belowground plant traits, especially root exudation, can help us to meet this challenge. Root exudates are a cocktail of different compounds that roots release into the soil. They are involved in important interactions with other plants, soil microbes and nutrient availability. In this paper, we highlight how crop wild relatives contain different root exudate traits compared with crops, which offers opportunities to reduce the use of fertilisers and pesticides.
Preece and Peñuelas (2020), Trends in Plant Science, 25(1), 14-21.
Drought and nutrient effects on soils
Soils, and their microbial communities, are being affected my multiple drivers of global change. In the Mediterranean region, drought and nutrient deposition are two important problems. We measured soil respiration and physiologically profiled microbial communities to test for the impacts of drought, and subsequent recovery, and how nitrogen and phosphorus addition affected this. Drought was a larger driver of changes to soil communities than N or P deposition. There were also differences in recovery capacity depending on the plant species growing in the soil.
Preece et al., (2020), Science of the Total Environment, 735, 139554.
Nitrate pollution and bryophyte diversity
Human activities are increasing nitrate pollution in groundwater. These aquifers are drained by springs which act as refugia for preserving biodiversity in the Mediterranean region. We studied 338 springs across a gradient of climate, nitrate and water conductivity. Nitrate pollution reduced the likelihood of finding a rare species in springs, and decreased diversity of mosses and liverworts at the regional scale. Warmer and drier springs also presented fewer bryophyte species. We show that the combination of nitrate pollution, increasing temperature and drought could severely threaten bryophyte diversity in Mediterranean springs.
Fernández-Martínez et al., (2020), Science of the Total Environment, 705, 135823.
Effects of past and current drought on soil communities
Drought impacts on soil microbes may depend both on current water stress and the history of previous drought. We set up a 10-level drought experiment to test the effect of water stress on 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. The current drought had greater negative effects on bacteria than fungi. Bacterial diversity was higher in soil with a history of drought than control soil, however, during new drought, abundance of some taxa fell more in historically droughted soil.
Preece et al., (2019), Soil Biology and Biochemistry, 131, 28-39.
Metabolites of root exudates under drought
Plants release a large variety of compounds into the soil, including primary metabolites (such as sugars, amino acids and organic acids) and secondary metabolites (such as phenolics, flavonoids and terpenoids). Exudate composition can vary due to abiotic stress such as drought. Using an ecometabolomics approach we identified the compounds in the exudates of Quercus ilex (holm oak) under an experimental drought gradient and subsequent recovery. Under drought, plant exudates consisted mainly of secondary metabolites, associated with plant responses to drought stress, whereas the metabolite composition under recovery shifted towards a dominance of primary metabolites. Changes in root exudation composition, both during drought and recovery, were highly dependent on the severity of water stress.
Gargallo-Garriga and Preece et al., (2018), Scientific Reports 8, 12696.
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