The world’s rate of population growth far exceeds any increase in agricultural production. Agriculture cannot keep up, and a key reason is water availability. To meet the population projected for 2050, agriculture will require 70 % more water than at present. Yet, 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 about 80 % of available fresh water, 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 in precise ways. Yet current irrigation management practices are limited when it comes to determining the optimal amounts of water for cropping under dry conditions. New irrigation methods will be necessary. Achieving this will require a full understanding of crop plants’ physiological response 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 undertaken with the support of the Marie Skłodowska-Curie programme. Key to studying plants’ physiological drought response is the concept of water stress. This essentially means that the plant is thirsty yet unable to get enough water. Then the plant will not be growing optimally. “It is essential to have the best indicator of plant water stress for precise irrigation scheduling,” explains project coordinator, Celia Rodriguez Dominguez. “This would indicate how much water should be applied for irrigation and at which times.”
Improving water stress monitoring
However, understanding water stress is complicated. Standard monitoring devices are ambiguous, also difficult to link with specific physiological responses. Most current indicators are unsatisfactory. To find a better one, AgroPHYS researchers used an array of pre-existing plant monitoring instruments to determine physiological processes. Most important and innovative of these were special cameras and microscopes, used to monitor the formation of air bubbles within olive tree seedlings’ vascular system as the plants dehydrate. Additionally, the team developed a novel combination of rehydration techniques, used to measure the movement of water from the soil-root to the leaf. New physiological insights from these observations were the most significant of the project’s results. Other major outcomes included demonstration that knowledge of agricultural species’ resistance to water stress is important under a climate change context. Nevertheless, high levels of stress would be unlikely in fruit trees, which avoid it by closing their stomata. Researchers concluded that the extent to which stomatal closure limits productivity depends on a plant’s underground capacity for water uptake. “We showed that stomatal conductance should be the target variable to monitor water stress in fruit trees,” adds Rodriguez Dominguez. In practice, if scientists could detect water stress in plants earlier, the crop would need less water, making irrigation more efficient. Furthermore, being able to relate water stress to the physiology of productivity enables researchers to customise irrigation strategies depending on the stages of growth. Using the sensors, small farmers will be able to increase yields and crop quality, while also saving water and improving water efficiency.
AgroPHYS, water stress, irrigation, agriculture, drought, crop plant, stomata, olive tree