What features of a cactus give an advantage in an arid climate?

What features of a cactus give an advantage in an arid climate? Suggest other ways plants can adapt to drought.

The living conditions in the desert are very difficult for plants, there is little moisture and very high daytime temperatures and low nighttime. In order to exist in such a climate, plants acquire a number of adaptations. For example, a cactus has modified leaves – needles, which allows it to dramatically reduce the area of ​​evaporation of moisture. Also, the cactus has a fleshy trunk in which moisture accumulates and remains. It seems to me that a more effective way of accumulating moisture would be accumulation in the roots, since it also significantly reduces evaporation.