The plant genome can respond rapidly and dynamically to stress in a manner that overcomes the restrictions of a highly stable DNA sequence. Abiotic stresses such as chilling, planting density, rubbing, cutting, and successive rounds of subculture generally decrease the levels of DNA methylation. The opposite effect is seen for salt stress, and the effects of heavy-metal stress are species specific. Biotic stres-ses such as pathogenic infection can lead to two contrasting effects on the levels of methylation in plants: hypermethylation on the genome-wide level and hypomethylation of resistance-related genes. Both phenomena may contribute to the adaptation of plants to stress. Although heritable methylation patterns and phenotypic variations that arise in response to stress are of potential value for plant breeding, their exploitation presents great challenges. The plant genome can respond rapidly and dynamically to stress in a manner that overcome that the restrictions of a highly stable DNA sequence. The opposite effect is seen for salt stress, and the effects of heavy-metal stress are species specific. Biotic stres-ses such as pathogenic infection can lead to two contrasting effects on the levels of methylation in plants: hypermethylation on the genome-wide level Both hypocenosis of resistance-related genes. Both hermeneuticals and phenotypic variations that arise in response to stress are of potential value for plant breeding, their exploitation presents great challenges.