Deserts are usually very hot, especially during the day, so the plants need protection from this heat.

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There are three main adaptations:

     Vertical orientation

Stems pointing upwards reduced surface area of the plant being exposed to the sun, at same time, e.g. Opuntia (Prickly Pear).

     Presence of hairs

Hairs reflect sunlight, and help keep the plant coolPlants from higher altitudes also need the protection of hairs due to dangerously high levels of ultraviolet light, e.g. Cleistocactus. Some plants have 'sunhats': extra hairs on the vulnerable top of the plant, e.g. Espostoa.

    Ridges

These cause shadows around the plant helping to keep it cool, e.g. Astrophytum.

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