The most likely physical change that would help a plant adapt to living in an area with little rainfall is developing a deeper root system. Here's why:

* Water absorption: Deeper roots allow the plant to access water sources that are further below the surface. This is crucial in arid environments where surface water is scarce.

* Stability: Deeper roots also provide better anchorage in loose, dry soil, making the plant more stable against strong winds.

Other possible adaptations include:

* Thicker, waxy leaves: These reduce water loss through transpiration.

* Reduced leaf surface area: Smaller leaves reduce the surface area exposed to sunlight and therefore reduce water loss.

* Succulence: Some plants store water in their leaves, stems, or roots for later use.

Let me know if you'd like to learn more about plant adaptations to dry environments!