are able to survive long dry periods. Such plants may close their stomata during the daytime and open them again at night. During the night, temperatures are much cooler, and plants will experience less water loss, and intake larger amounts of carbon dioxide for photosynthesis. Adaptations in xerophytes include resistance to heat and water loss, increased water storage capabilities, and reduced surface area of leaves. One of the most common families of desert plants are the cacti, which are covered in sharp spines or bristles for defence against herbivory. The bristles on certain cacti also have the ability to reflect sunlight, such as those of the old man cactus. Certain xerophytes, like oleander, feature stomata that are recessed as a form of protection against hot, dry desert winds, which allows the leaves to retain water more effectively. Another unique adaptation can be found in xerophytes like ocotillo, which are "leafless during most of the year, thereby avoiding excessive water loss". There are also plants called phreatophytes which have adapted to the harsh desert conditions by developing extremely long root systems, some of which are 80 ft. long; to reach the water table which ensures a water supply to the plant. Exploration and research The harsh climate of most desert regions is a major obstacle in conducting research into these ecosystems. In the environments requiring special adaptations to survive, it is often difficult or even impossible for researchers to spend extended periods of time investigating the ecology of such regions. To overcome the limitations imposed by desert climates, some scientists have used technological advancements in the area of remote sensing and robotics. One such experiment, conducted in 1997, had a specialised robot named Nomad travel through a portion of the Atacama Desert. During this expedition, Nomad travelled over 200 kilometres and provided the researchers with many photographs of sites visited along its path. See also Aridisols References Deserts Ecology Ecology by biome Habitats