Functional imaging of biophoton responses of plants to fungal infection

Abstract

Each living cell of a plant produces photons in certain conditions. Under normal physiological conditions, cell photon emission is stationary and minimal. Disturbance in the oxidative homeostasis by biotic stress is manifested by increased ‘biophoton’ production. Such biophoton responses of plants may be used as an integral indicator of the degree of oxidative homeostasis misbalance. Our results demonstrate that biophoton generation has been much higher in a resistant potato variety than in a susceptible one till 10 h after Phytophthora infestans inoculation. In contrast, ultra-weak luminescence from detached susceptible potato and moderately resistant pelargonium leaves increased from 1–4 to 4–5 days after inoculation with Phytophthora infestans or Botrytis cinerea, respectively. Pre-treatment of susceptible potato leaves with a defence inducer, arachidonic acid, resulted in a transient burst of light in response to P. infestans lasting for 30–45 h post inoculation (hpi). This study presents the potential adaptation of functional imaging of ultra-weak luminescence to monitor time-dependent free radical processes during disease development and its application to draw conclusions on plant resistance to pathogens of different lifestyle. Moreover, it has been shown that imaging of temporal biophoton generation from potato leaves treated with arachidonic acid might be a helpful marker in mapping oxidative changes leading to systemic acquired resistance (SAR).