In this case, the voltage arises because the crystal deforms and a symmetry between positively and negatively charged atoms is disturbed.

ECONOMIST: Predicting earthquakes

That's partly due to liquefaction but it's mainly due to the way the Earth deforms when you snap it like an elastic band.

BBC: Christchurch quake mapped from space

Specifically they discovered that Pythium ultimum, a fungus that attacks aubergines, peppers, lettuces, tomatoes and cucumbers as seedlings, Clavibacter michiganensis, a bacterium that kills young plants and deforms fruits, and Streptomyces scabies, a second bacterium, which causes potatoes to develop revolting scabs and for which no treatment currently exists, all stopped growing in the presence of the oil.

ECONOMIST: Tobacco extracts protect plants from pests and pathogens