This book contain 14 chapters covering the impacts of abiotic stresses on plant cell metabolisms including their roles in the generation of reactive oxygen, nitrogen and sulfur oxidant species. How, where and when such oxidants are generated in cells during their biochemical reactions. The mechanisms by which these oxidants are generated in peroxisomes, mitochondria and chloroplasts. How varying enzymes are implicated in the generation of oxidant including their homeostasis. Finally, oxidant generations caused by environment fluctuations are also reported.