During adverse season, 'therophytes ' survive by :

Seeds

Therophytes are said to be those plants that are annual, complete their life cycle in a short period of time, and are able to withstand extreme conditions in the form of seeds. These plants are generally found in places like the deserts. So, during adverse conditions therophytes survive by seeds. This is advantageous because seeds have a tough seed coat which protects the embryo from the extreme conditions outside. As well as the seed is in dormancy with minimum metabolism and only 10-15% water in it.