Articles
EARLY WATER STRESS ASSESSMENT AND AUTOMATIC IRRIGATION SYSTEM OPERATION BASED ON ELECTRICAL SIGNALING IN FRUIT TREES
We have developed an Ag/AgCl micro-electrode enabling the continuous measurement of plant electric potential differences in fruit trees, in response to changes in micro-environmental conditions related to light, temperature and soil water availability.
Electric action (AP) and variation (VP) potentials have been detected in tree trunks; most AP ranged -5 to -200 mV, and lasted from a few milliseconds up to 1 min, with a very short lag time after the stimulus is imposed.
In most cases, AP were followed by long term (1 to 10 h) distinct VP. Our results indicate that there is a clear, fast and accurate electrical signalling mechanism within the plant, which is positively correlated to the intensity and duration of micro-environmental stimuli modifying plant water potential, water stress and light conditions.
Several avocado (Persea americana Mill.) cultivar Hass trees, placed in a Faraday cage in an environmentally-controlled greenhouse, were used in this research.
In the trunk, significant changes in EP at 25 and 85 cm above the soil surface have been measured, in response to short- and long-term drought; an extra-cellular electrical signal travels through the phloem at speeds in the range of 1.8 to 2.4 cm min-1.
Applications of this signalling mechanism as an early detector of plant water stress are discussed and many questions regarding the role of electrical signals in eliciting physiological responses in fruit tree species are proposed.