how can the plants like cactus and Acacia live in deserts with scarce water

It's adaptations are:-

1.Leaves modified to thorns to reduce loss of water

2.It has very good root system that goes deep down in search of water to absorb it

3.It has a green stem to perform photosynthesis.

4.It's stem stores the water.

5.It's thorns also work like protectors as the thorns protect the stem from animals as animals can drink the water.