The adaptations are:
Succulence:
Succulent plants have fleshy and thick leaves, stems or roots. That is because inside thos plant parts, water is being stored. Examples are the cactus, agave, aloe, elephant trees and all cactus are succulent plants. These plants are able to absorb large quantities of water because desert rains are very light and brief so they have to do so in order to survive. The ground soil will also dry rapidly under the intense heat of the sun.
Drought Tolerance:It refers to the ability of a plant to withstand desiccation, which means to be dried up, without dying. Plants using this adaptation usually have deciduous leaves, where leaves are shed during dry periods to prevent too much water loss through transpiration at the leaf surfaces and to retain more water in their stem. Drought tolerant plants also have more extensive shallow roots.
Drought Avoidance:
Annual plants mature in a single season and die after using all their energy to produce seeds. These plants are only found in countries with dry seasons and the more arid the habitat, the greater proportion of annual species of plants. It is usually flowers that make use of drought avoidance and certain of these flowers only bloom in the night time as it is cooler at night. Thus, more insects will come out so pollinations occurs and there will be more of the flowers even if they die quickly.
Annual plants mature in a single season and die after using all their energy to produce seeds. These plants are only found in countries with dry seasons and the more arid the habitat, the greater proportion of annual species of plants. It is usually flowers that make use of drought avoidance and certain of these flowers only bloom in the night time as it is cooler at night. Thus, more insects will come out so pollinations occurs and there will be more of the flowers even if they die quickly.
Types of roots:Desert plants have long or deep roots that help them absorb as much water as possible from the ground. They also tend to have roots that spread a long way and sometimes exist in a suspended state until rain activates them. A small amount of moisture will cause the root feeders to grow quickly out of the main roots. Those feeders are what brings in the water, nutrients and dissolved minerals in the soil or ground. The feeders actually die after the rain is gone and when the soil dries up. This actually happens to enable the plant to live on its stored water without having to use up energy and moisture and keeping the roots alive may not be needed for several months.
Types of leaves:
Desert plants have waxy cuticles that make them almost waterproof when the stomata is closed so water is conserved. Other plants have small, spiny leaves that reduce the amount of water loss during transpiration. Some cactus also make use of their light coloured leaves or hairs to shade from the sun.
Keeping away thirsty animals:
Some desert plants grow in inaccessible areas and can camouflage. They also have poisonous or toxic leaves to keep away predators, who want to consume the stored water in fleshy plant parts.
Growth:
Desert plants can survive with little water but even so, some of them grow near oases, which are surfaces which water come out from underground, or rivers, that fill up after rainstorms. They also grow slowly because less energy will be required. Thus, less water is used up and they would be able to survive for a longer time.
Links:
Book:
Alpha Books: Deserts
Alpha Books: Deserts
Pictures:
http://cache2.artprintimages.com/p/LRG/27/2746/5RDTD00Z/dee-ann-pederson-saguaro-cactus-in-sonoran-desert-saguaro-national-park-arizona-usa.jpg 
Sources: 
