CLASSES OF SIGNALS. “Not only hydraulic and chemical signals, but also electrical signals act on the perception of environmental stimuli and trigger biochemical and physiological changes such as elongation, growth, water transport, displacement of substances in phloem, reduction of turgor pressure, variation of photosynthesis, respiration, and gene expression, mediating the relation between the plant and its external environment.”
http://link.springer.com/article/10.1007/s11738-015-1950-4