Biophysical methods used to generate tolerance to drought stress in seeds and plants: a review

Drought stress has serious repercussions for agriculture, affecting crop growth with low yield effects concerning food production and food security. The main objective of this research is to conduct a scientific literature review of the physical methods used to generate tolerance to water stress in crops. (i) The most widely applied physical method to counteract the effects of drought stress is UV radiation, magnetic field application (18%), He-Ne and CO 2 laser (18%), gamma radiation (9%) and plasma (6%). (ii) Treatments with ultraviolet light and magnetic fields have been applied mainly in cereals, vegetables, legumes, medicinal plants, and trees. Also, He-Ne, CO 2 laser, and plasma in seeds in cereals and medicinal plants in the pre-sowing stage to seed level. Finally, gamma radiation has been applied to plants and seeds (grass, flowers, sugar plant). (iii) The reported physical methods can increase or decrease the biochemical variables under water stress depending on the physical method and radiation parameters applied, as well as the crop, level of drought and the environment in which the plants develop. Thus, UV radiation, magnetic fields, gamma radiation, and He-Ne and CO 2 lasers are physical methods that produce seed and plant improvement effects.