IMPACT OF STRESS. “Evidence is accumulating that both biotic and abiotic stresses induce a heritable increase in the ability of plants to withstand infection and tolerate stress. DNA damage, pathogen infection, and abiotic stresses also increase homologous recombination frequency and chromosomal rearrangements, both somatically and heritably.”
http://science.sciencemag.org/content/338/6108/758