Annual plants that grow in climates with long periods of drought followed by brief periods of rain have evolved several physiological adaptations to help them survive under such conditions. One such adaptation is the ability to quickly germinate, grow, and reproduce during the brief rainy periods, and then die before the next extended drought.
Another adaptation is the ability to store water in their tissues to help them survive during the dry periods. Some annual plants have developed specialized water-storage tissues, such as succulent leaves, stems, or roots, to help them survive extended drought periods.
Additionally, some annual plants have developed deep root systems that allow them to access water from deeper soil layers during drought periods. These root systems can also help anchor the plant in place during high winds or storms.
Finally, some annual plants have developed the ability to enter a dormant state during the dry period, in which they shut down their metabolic processes and wait for the next rainy period to resume growth and reproduction.
Overall, the physiological adaptations of annual plants in climates with long periods of drought followed by brief periods of rain allow them to survive and reproduce in challenging environmental conditions.