Try doing your research on the web, from google. I think the search string: plant adaptations drought
would get quite a bit.

They have a variety of mechanisms, some chemical, some physical.

Yes you are correct. some plants have thicker leaves with less pores (stomata) in them and therefore do not allow the leaves to breathe as much. Mother Nature has a pretty unique system. Even grasses that can go completely brown and you think that they have all died, but all they have done is just gone dormant. I live in good ole Southern Alberta on the praries, it can either be wet or dry, never seems to be a happy medium, it always amazes me how the natural native grasses can go so brown and still remain alive. Next time they get some rain or other moisture, up and away they go again. That is the reason when planting things like that, a person has to do their homework and plant the right varieties.

cwjg,

I would recommend a google search on "crassulacean acid metabolism" this is the preferred method among succulents.

Other adaptations are dormancy or near dormancy during the driest part of the year. Some drop their leaves entirely, others have thick, leathery leaves that reduce transpiration only carrying on enough photosynthesis to remain alive.

Some have very wide ranging efficient roots while still others, less efficient, form mutually beneficial relationships with soil fungi called mycorrhizal symbiosis.

Many times, a plant utilizes more than one survival strategy.

One additional adaptation is simply to avoid the drought entirely. Many wildflowers grow quickly, flower and set seed during the short time that moisture is available.

Another method not mentioned, is long taproots that go deep into the ground. Likewise, some plants have huge tubers underground that act as a sort of water reservoir.

Gray leaves and leaves with waxy coatings are other methods to conserve water loss from transpiration.