H2020 AgroPHYS Project: Understanding how plants overcome drought by controlling stomatal function: applicability and impacts in agriculture
- Type Project
- Status Filled
- Execution 2017 -2020
- Assigned Budget 263.440,8 €
- Scope Europeo
- Main source of financing H2020
- Project website AgroPHYS
Drought can cause significant economic losses due to decreased productivity. Therefore, the new insights into how plants cope with drought resulting from AgroPHYS results will have a major impact on reducing these economic losses by optimizing water use in agriculture and even improving the quality of the final product. For example, in agriculture, there is an irrigation strategy called Regulated Deficit Irrigation (RDI), which is based on applying exactly the water required by a crop at each phenological stage. It is known that depending on the stage of the crop, it will be more or less resistant to drought.
These strategies can be greatly optimized by improving the physiological understanding behind these different resistances at different phenological stages. Furthermore, this knowledge will allow us to place the outputs of plant sensors in a physiological context, allowing us to monitor these physiological variables over time and use them as inputs to improve climate change predictions in plants through mechanistic models and to provide new hypotheses for testing. However, this will only be possible if there is good communication between physiologists and agronomists to improve irrigation strategies, between them and engineers and companies to minimize the costs of agricultural technologies, and between these and mathematicians and modelers to translate physiological mechanisms into equations.
The first results obtained during the Exit Phase were: (1) the optical technique was used for the first time to simultaneously monitor xylem embolism formation in roots, stems, and leaves in whole, intact olive seedlings; (2) roots were identified as the organs most resistant to the formation of these embolisms, in contrast to previous studies that pointed to roots as more vulnerable tissues than central tissues (stems); and (3) a relatively high variation in resistance was found among individuals, between tissues, and within tissues.
Since the impact of plant hydraulics on stomatal function was not assessed in this work, a specific experiment was also conducted in olive to determine whether the hydraulic pathway from soil to leaf is dynamic or static during stomatal closure. Outcomes included: (1) the development of a novel hydraulic method to partition soil-to-leaf hydraulic pathways, and (2) an observed decrease in root water transport capacity under moderate drought conditions that functioned as a hydraulic signal to limit stomatal opening, helping the plant conserve water and isolating it from the drying soil.
Directly related to AgroPHYS, we expanded our knowledge of how hydraulic traits can be decisive in protecting plants against the negative effects of drought by working with different olive genotypes. Furthermore, we also addressed the application perspective of AgroPHYS through the development of robust, physiologically based tools for irrigation management, demonstrating that the combination of the three main research fields of AgroPHYS is not only possible but fundamental to advance the optimization of water use in agriculture. In addition to these direct AgroPHYS results, and thanks to participation in Synchrotron-based campaigns, we demonstrated that the optical technique was as effective as hydraulic and microtomography techniques in measuring hydraulic resistance thresholds of water stress.
Throughout the Incoming Phase, experiments focused primarily on applying the new plant physiological knowledge acquired during the Outgoing Phase in the IRNAS-CSIC experimental orchard "La Hampa." Six fruit tree species were extensively physiologically characterized and monitored with meteorological, soil, and plant sensors.
As a summary of the overall results of AgroPHYS, we can say that (1) knowing the resistance of agricultural species to water stress is fundamental in a context of global change; (2) however, these levels of water stress should not be reached in fruit tree orchards and, in fact, plants avoid it by closing their stomata; (3) the limitations in productivity derived from this stomatological closure seem to be related to the underground water absorption capacity; and (4) we demonstrated that stomatal conductance should be our target for monitoring water stress in fruit orchards.
The exploitation and dissemination of these results has been addressed through their presentation at several International Xylem Meetings, in seminars at both the University of Tasmania and Research Centers in Spain, initiating a collaboration with soil scientists at the University of Bayreuth (Germany), and publishing several articles in high-level journals, giving additional support to our conclusions.
We are currently experiencing a global crisis where the growing world population and, consequently, the demand for food are placing agriculture in a context of urgency because it will need to produce this food without wasting the water needed for its production. Furthermore, the climate crisis and increasing water scarcity, considering that agricultural water use can account for up to 80% of available freshwater, make it essential to improve agricultural practices and develop more efficient irrigation strategies.
Increasingly frequent and severe drought events cause plant water stress, a functional and structural response of plants to low water availability that reduces crop productivity. Therefore, understanding the impact, mechanisms, and characteristics underlying drought tolerance in agricultural plant species is essential to increasing the efficiency of irrigation strategies and improving productivity. The impacts of this on society are direct and represent key European priorities: optimizing agriculture in a changing climate with reduced water availability and a growing population.
The AgroPHYS project aims to combine three important areas of research (diagram attached) to address this urgent need: a fundamental understanding of the physiological mechanisms of plant responses to drought, the use of plant sensors to monitor these responses in real time, and the implementation of physiologically based models to predict the impacts of global change on plants and provide new hypotheses for testing.
The conclusions of the action can be summarized as follows: (1) the use of an optical technique to visualize in vivo airlock formation within the vascular system as olive seedlings dehydrate, allowed to demonstrate that roots were the most resistant organs to hydraulic dysfunction; (2) the results obtained from this easy-to-use and low-cost optical technique are in agreement with the most common hydraulic techniques and with synchrotron-based high-resolution techniques; (3) stomatal opening limitations appear to be related to a decrease in soil-root hydraulic conductance under moderate levels of water stress in olive trees; (4) abscisic acid production in leaves is crucial to protect vessels from airlock formation, as it plays a key role in triggering stomatal closure; and (5) with a combination of mechanistic models and leaf turgor pressure sensors, automatic and continuous monitoring of stomatal conductance in fruit tree species is possible, which will improve the water used by these fruit orchards.
Terrestrial plants have coped with drought since they first colonized dry land. Drought is the most common cause of water stress, a functional and structural response of plants to low water availability. Understanding the impact, mechanisms, and traits underlying drought tolerance in agricultural plant species is essential for improving productivity and furthermore represents a major European priority (SFS-01-2016): optimizing agriculture in a changing climate with reduced water availability and a growing population.
To address this urgent need, it is necessary to first understand how stomata regulate gas exchange in leaves, as stomata are the main limitation of photosynthesis in crops under water stress. Both hydraulic and non-hydraulic or hormonal signals are the main drivers of stomatal regulation. Therefore, AgroPHYS proposes to investigate how these signals interact to protect plants against harmful desiccation. This project will generate physiological knowledge, at UTAS, from a series of experimental techniques and apply it to a physiologically based model and a plant-based automatic sensor to guide both irrigation management and research, at IRNAS-CSIC.
The objectives of AgroPHYS are (i) to assess the relative importance and coordination of hydraulic and hormonal signals in plant stomatal responses to drought and recovery, and (ii) to apply this knowledge, using a mechanistic model and a plant sensor, to predict productivity relative to water consumption in agricultural plant species with different water use strategies.
The outgoing research group is at the forefront of physiological research, and the learning environment will provide the candidate with maximum benefit and excellent opportunities to interact with researchers from around the world. These skills and knowledge will be transferred back to IRNAS-CSIC, providing essential data not only for scientific research on plant function but also for precision agriculture and optimal irrigation management.
The global population growth rate far outpaces any increase in agricultural production. Agriculture cannot keep pace, and a key reason is water availability. To meet the projected population by 2050, agriculture will require 70% more water than it does today. However, that water will generally not be available. Many parts of the world, including Europe, face reduced water availability due to climate change. In arid and semi-arid countries, agriculture already consumes around 80% of available freshwater, and it will consume even more as climate change takes hold. Therefore, agriculture must become more efficient. Europeans will have to start irrigating crops—and irrigate them precisely.
However, current irrigation management practices are limited when it comes to determining optimal crop water quantities under dry conditions. New irrigation methods will be necessary. Achieving this will require a thorough understanding of the physiological response of crop plants to drought.
Water stress and drought response. The EU-funded AgroPHYS project investigated this response and used mechanical sensors to monitor it in real time. The research was carried out with support from the Marie Skłodowska-Curie program. Key to studying the physiological response of plants to drought is the concept of water stress. Basically, this means that the plant is thirsty but cannot obtain enough water.
The plant will then not grow optimally. "It's essential to have the best indicator of plant water stress for accurate irrigation scheduling," explains project coordinator Celia Rodríguez Domínguez. "This would indicate how much water to apply for irrigation and when." Improving Water Stress Control However, understanding water stress is complicated. Standard monitoring devices are ambiguous and difficult to relate to specific physiological responses.
Most current indicators are unsatisfactory. To find a better one, AgroPHYS researchers used a series of pre-existing plant monitoring instruments to determine physiological processes. The most important and innovative were special cameras and microscopes, used to monitor the formation of air bubbles within the vascular system of olive seedlings as the plants dehydrate. In addition, the team developed a novel combination of rehydration techniques, used to measure the movement of water from the root in the soil to the leaf.
The new physiological insights gained from these observations were the most significant results of the project. Other important outcomes included the demonstration that understanding the resistance of agricultural species to water stress is important in the context of climate change. However, high levels of stress are unlikely to occur in fruit trees, which avoid it by closing their stomata. The researchers concluded that the degree to which stomatal closure limits productivity depends on a plant's belowground water uptake capacity. "We demonstrated that stomatal conductance should be the target variable for monitoring water stress in fruit trees," adds Rodríguez Domínguez.
In practice, if scientists could detect water stress in plants earlier, crops would require less water, making irrigation more efficient. Furthermore, being able to relate water stress to the physiology of productivity allows researchers to customize irrigation strategies based on growth stages. With sensors, smallholder farmers will be able to increase crop yield and quality while saving water and improving water efficiency.
- AGENCIA ESTATAL CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS (CSIC)
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