there is a vast diiference in temperature in the day and night at the desert, so how do plants in the desert survive the cold temperature at night?
November 22nd, 2009
As Deserts Are Extremely Cold At Night, How Do Plants Like Cactus Survive The Cold Night In The Desert?
Posted in Desert Shrubs 
Tags: Cactus, Cold, Desert, Deserts, Extremely, Like, Night, Plants, Survive
Desert plants must be adapted to the dry conditions found in arid environments. Some of the most common adaptations are:
Reduction of leaves, often into spines for protection (above). The flat surface of normal leaves provides a huge area for water loss.
Development of the stem as a major photosynthetic structure (above right and right). With leaves reduced, photosynthesis has to occur somewhere.
Water storage in the stem (above, right). Water is needed for many things; if the plant is to have it available it must be stored.
Development of defense structures (above, right, below right). The most common are reduced leaves that take on the form of spines, but chemical defenses are also very common. With less photosynthesis taking place, growth of desert plants is often very slow, and under these conditions it is advantageous for the plants to make greater investments in defense.
Coating the plant with a thick waxy cuticle (above and below right). This helps reduce water loss.
A dense coating of hairs (trichomes) (below). This slows air moving over the surface of the plant; since air in the desert is very dry any air movement tends to increase evaporation. The trichomes create a microlayer of humid air around the pant, particularly in the vicinity of the stomata.
Extensive underground root systems (not shown). These roots can either grow straight down to groundwater, if it is available, or spread out extensively under the surface of the desert. The latter growth form allows the plant to take advantage of short, intermittent rains. Key in this strategy is elimination of competitors’ roots; many desert plants inject toxic chemicals into the soil to kill their competitors roots, a phenomenon known as allelopathy.
Cacti are CAM Plants. CAM plants open their stomata (its own ’sweat pores’) at night and not during the day. Stomata let them respire. At night the heat drops, which drops its rate of water loss.
Cacti use a special form of photosynthesis called Crassulacean Acid Metabolism (CAM). CAM is named for the crassula family (Crassulaceae), a group of plants exhibiting the process. In plants, the pores, or stomata, of plants allow for gas and water vapor exchange with the environment. Arid plants need to conserve water vapor during the day, so these stomata remain closed until nightfall. The lower temperatures, lack of sunlight, and lower wind speed at night provide optimal conditions for CAM plants to open their stomata without risk of excessive water loss. At night, the opened stomata take in carbon dioxide (CO2) for use by the plant. Without the sun, the energy source for photosynthesis, CAM plants can’t make sugars at night, so, the CO2 is processed into malic acid for storage in the cell vacuoles. During the sunlight hours, the plants breaks down this acid and the resulting CO2 is used to produce carbohydrates (sugars) for the plant via a process known as the Calvin cycle. The Calvin cycle produces sugar for the plant according to the photosynthesis equation: 6CO2 + 12H2O + Sunlight –> C6H12O6 + 6O2 + 6H2O, or carbon dioxide + water + light energy yields sugar (Glucose) + oxygen + water.