PLANT ADAPTATIONS

• All but the most arid desert lands support life that is frequently abundant and well adapted to the scarcity of water and the daytime heat.
• Desert plants have evolved ways of conserving and efficiently using the water available to them.
• Some flowering desert plants are ephemeral; they live for a few days at most.
• Their seeds lie dormant in the soil, sometimes for years, until a soaking rain enables them to germinate and quickly bloom.
• Woody desert plants either have long root systems that reach deep water sources or have spreading shallow roots that are able to take up surface moisture quickly from heavy dews and occasional rains.
• Desert plants usually have small leaves.
• This conserves water by reducing surface area from which transpiration can take place. Other plants drop their leaves during the dry period.
• The process of photosynthesis—by which sunlight is converted to energy and usually conducted primarily in leaves—is taken over in the desert by the stems.
• A number of desert plants are succulents, storing water in leaves, stems, and roots.
• Thorns, which are modified leaves, serve to guard the water from animal invaders.
• These plants may take in and store carbon dioxide only at night; during the day their stomata, or pores, are closed to prevent evaporation.
• Desert plants growing on saline soils may concentrate salt in their sap and then secrete the salt through their leaves.