A method for increasing drought tolerance in a plant or photosynthetic organism is provided, where the tolerance is increased by applying an effective amount of trimethylamine N-oxide (TMAO) or trimethylamine N-oxide di-hydrate, or a TMAO chemical derivative, or a TMAO chemical analogue and thereof to a plant, seed or photosynthetic organism that has been exposed to or to be exposed to water stress conditions. Water stress tolerant plants or photosynthetic organisms produced through the application of trimethylamine N-oxide (TMAO) or trimethylamine N-oxide di-hydrate, or a TMAO chemical derivative, or a TMAO chemical analogue to a plant or photosynthetic organism are also disclosed.
