So what type of plants are able to survive in extreme conditions in places such as, the north and south poles and deserts? Well, depending on the place, there are some amazing plants that are able to survive, not exactly thrive, in EXTREME WEATHER CONDITIONS.

Antartica:

The extreme conditions in Antartica make it a habitat which only the hardiest survive. Very few species have been recorded on the 2% of the continent that is ice-free. They include about 150 lichens, 30 mosses, some fungi and one liverwort.

Deserts:

To survive, desert plants have adapted to the extremes of heat and aridity by using both physical and behavioral mechanisms, much like desert animals.

Plants that have adapted by altering their physical structure are called xerophytes. Xerophytes, such as cacti, usually have special means of storing and conserving water. They often have few or no leaves, which reduces transpiration.

Phreatophytes are plants that have adapted to arid environments by growing extremely long roots, allowing them to acquire moisture at or near the water table.

Other ways that plants survive:

In the desert, it's so hot, it's no wonder that hardly any plants grow there. Succulent plants such as cacti, aloes, and agaves, beat the dry heat by storing plenty of water in their roots, stems, or leaves.

When it does rain, succulents absorb as much water as they can, as quickly as possible. In the desert, water evaporates rapidly, never sinking deep into the soil. Thus, most succulents have extensive, but shallow root systems. Their roots absorb water just a half inch or so below the surface.

Succulents have evolved a number of strategies for holding onto this water. They tend to have a thick waxy coating, which helps seal in moisture.

All plants are covered by tiny pores called stomates, which allow plants to take in gasses for photosynthesis. However, these pores also allow water to be lost. Succulents have fewer stomates per cubic inch through which water can evaporate. In addition, succulents have a reduced surface area and, if they have leaves at all, they’re thick and fleshy.

Many succulent plants also have a modified way of conducting photosynthesis. Other plants open their stomates during the day to take in carbon dioxide for photosynthesis. Many succulents, however, keep their stomates closed during the heat of the day and open them in the coolness of the night to take in carbon dioxide, which they store until the next day.

Finally, because water is a scarce commodity in the desert, succulents have to protect themselves against thirsty animals. These plants protect their water supplies by being prickly like many cacti or in other cases, by being toxic, by growing in inaccessible locations, or by camouflage.

Sources:

http://indianapublicmedia.org/amomentofscience/how-plants-survive-in-the-desert/

http://www.desertusa.com/du_plantsurv.html

http://library.thinkquest.org/26442/html/life/plant.html