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Plant
Adaptions
Plant
Adaptations
Desert plants, since they are rooted in place, must
cope with extremes in temperature, water availability
and solar radiation physiologically rather than behaviorally.
In fact, surface temperatures in direct sunlight are
commonly 25 to 50 degrees F warmer than the air temperature
six feet above. Most desert plant adaptations seem to
be geared towards minimizing water loss: a difficult
task since plants must "breathe" (collecting
Carbon Dioxide from the air) in order to photosynthesize,
losing body water to the atmosphere in the process.
Drought
Escapers
Drought escapers are plants that make use of favorable
growing conditions when they exist. These plants are
usually annuals and complete their life cycles in a
matter of days or weeks when water is plentiful enough
for them to do so. Seeds may lie dormant for years if
conditions are not favorable. Most grasses are "escapers,"
as are the spring wildflowers that sometimes bloom during
April and May.
Drought
Resistors
Drought resistors are typically perennials. Many perennials
have small, spiny leaves which reduce the impact of
solar radiation; others may drop their leaves when water
is unavailable. Spines and hairs on leaves act as a
buffer against warm air currents, limiting the amount
of water lost to evaporation. Plants also use "solar
tracking" to regulate their exposure to the sun.
Cacti store water within their bodies and have extensive,
shallow root systems that are able to soak up rainwater
quickly. Yucca have extensive tap roots that are able
to use water beyond the reach of other plants. Moss,
a plant not commonly associated with deserts, thrives
because it can tolerate complete dehydration: when rains
finally return, the plant greens up almost immediately.
Another extreme adaptation can be found in the utah
juniper tree, one of the most common plants in the southwest.
During a drought, junipers can self-prune, shutting
off water flow to one or more their branches in order
to conserve enough water for the rest of the tree to
survive.
Drought
Evaders
Drought evaders take advantage of wetter "micro
climates" found in the desert. Monkey flower, columbine,
easter flower, and ferns are found in well-shaded alcoves
near seeps or dripping springs. Cottonwood, willow and
cattail all require lots of water, and only grow in
riparian areas where their roots can reach the water
table easily.
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