How Plants Survive

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How Plants Survive in the Desert
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Life on the desert is hard.
2 major challenges
LACK OF WATER
HIGH/LOW TEMPERATURES
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2 MAJOR STRAGEGIES
succulent plants
store water in tissues
NON-succulent plants
grow fast, avoid drought
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SUCCULENTS
MUCILLAGE CELLS

• store water

• have thin flexible cell walls

• can readily change size
• and shape

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STOMATES pores for O2, CO2 exchange
SUCCULENTS
depressed into epidermis
thick waxy cuticle
UV reflectance
may be a layer of resin instead
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NON-succulent stomates
MANY stomata per area
not necessarily depressed into epidermis
help maximize photosynthesis
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CAM- photosynthesis
stomates open at nightime
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SMALL LEAVES
LESS SURFACE AREA ? LESS
EVAPORATION
brickellia bush leaf
dime
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LEAVES
cooling
NARROW LEAVES
? stay cooler
BLADE-LIKE LEAVES
? less area hit by direct sunlight
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PHOTOSYNTHETIC STEMS
stems rich in chlorophyll
less vulnerable to wind damage than leaves
less vulnerable to herbivores than leaves
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ROOTS

• may tap groundwater sources

• very efficient capture of rainwater

• in some areas as much as 75 of the water from
  low intensity rainstorms

• i.e. junipers

G R O U N D W A T E R
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ROOTS drought avoidance
Many non-succulents are dormant for much of the
year.
leafless
almost no growth
nutrients stored in roots
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SEEDS drought avoidance

• most seeds can survive long droughts

• most germinate ONLY after rainfall

• once germination occurs, growth is
• very rapid

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SPREADING OUT

• reduces competition
• moisture
• nutrients

• some plants may excrete chemicals
• poisonous to other plants

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desert oddball
orientation of barrel cacti

• barrel cacti tip southwest

• reduced exposure to direct
• sunlight

• some cacti fall over

Other plants change leaf orientations instead.
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SUMMING UP...

• Combinations of desert plant adaptations
• i.e. small leafs, succulent tissue
• vary depending on the environment in
• which the plant may be found.
• i.e. groundwater area vs. dunes

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THE END