Electrophysiological assessment of water stress in fruit-bearing woody plants

Abstract

Development and evaluation of a real-time plant water stress sensor, based on the electrophysiological behavior of fruit-bearing woody plants is presented. Continuous electric potentials are measured in tree trunks for different irrigation schedules, inducing variable water stress conditions; results are discussed in relation to soil water content and micro-atmospheric evaporative demand, determined continuously by conventional sensors, correlating this information with tree electric potential measurements. Systematic and differentiable patterns of electric potentials for water-stressed and no-stressed trees in 2 fruit species are presented. Early detection and recovery dynamics of water stress conditions can also be monitored with these electrophysiology sensors, which enable continuous and non-destructive measurements for efficient irrigation scheduling throughout the year. The experiment is developed under controlled conditions, in Faraday cages located at a greenhouse area, both in Persea americana and Prunus domestica plants. Soil moisture evolution is controlled using capacitance sensors and solar radiation, temperature, relative humidity, wind intensity and direction are continuously registered with accurate weather sensors, in a micro-agrometeorological automatic station located at the experimental site. The electrophysiological sensor has two stainless steel electrodes (measuring/reference), inserted on the stem; a high precision Keithley 2701 digital multimeter is used to measure plant electrical signals; an algorithm written in MatLab(®), allows correlating the signal to environmental variables. An electric cyclic behavior is observed (circadian cycle) in the experimental plants. For non-irrigated plants, the electrical signal shows a time positive slope and then, a negative slope after restarting irrigation throughout a rather extended recovery process, before reaching a stable electrical signal with zero slope. Well-watered plants presented a continuous signal with daily maximum and a minimum EP of similar magnitude in time, with zero slope. This plant electrical behavior is proposed for the development of a sensor measuring real-time plant water status.

Plant-Based Methods for Irrigation Scheduling of Woody Crops

“…A different system was described and tested in cucumber plants under greenhouse conditions by Wang et al [200]. Recently, Ríos-Rojas et al [201,202] developed a system for remote, real-time recording of plant electrical potential in the field and data transmission via Internet. The authors concluded that their system could be used to monitor water stress and, combined with soil moisture and potential evapotranspiration sensors, to schedule irrigation.…”

Use of plant woody species electrical potential for irrigation scheduling

“…39 In Figure 1C and 2C, the climatic effect on EP in well-watered plants (red line) is observed with successive changes in the slope of the daily maximum EP values, in coordination with changes in air temperature and solar radiation ( Fig. 1A and B; 2A and B).…”

“…According to reports by 3,4,26,39 plants respond electrically to stimuli generated in its micro-environment, and strong evidence indicates that soil water availability directly influences the electrical response of plants. Our results sustain these early reports.…”

“…Results reported by Rios-Rojas, 39 indicate that woody plant responses to soil water restricted availability can be detected by its EP behavior, opening the possibility to use EP as a sensitive water stress indicator that integrates plant water stress in relation to soil water availability conditions.…”

Effect of Water Stress on Seed Germination of Thymus serpyllum L. from Tessala mount

“…The negative effect of water stress on germination was reported by many authors for severals plants species (Amara et al, 2013;Rios-Rojas et al, 2014;Zhou et al, 2015). For this species, water soil has more complicated effects on germination than temperature because water is the initial factor for seed imbibitions and germination; it is directly and indirectly involved in subsequent germination metabolic stages (Cavalcante and de Perez, 1995) in particularly under arid and semi arid environment.…”