Question

how can the plants like cactus and acacia live in deserts with

Answer 1

because of their long tiny roots and absence of leaf

Answer 2

Cactus are not born directly from seeds they are first borned under the sand, after 1 to 2 weeks later they come out while this process goes on the cactus grows their roots very deep inside the sand after some weeks the roita found water inside the sand as they can now easily love in desert.
Please note That cactus can have a dangerous insect on it, it looks like a pin.