How do desert plants get enough water to live?
Photo: Kevin Eddy
Some deserts are extremely cold, others are hot – but all are very dry. That’s why, if you’re a desert plant, your biggest problem is water – how to get it and how to keep it.
In some deserts, it may not rain for twelve months at a stretch. When the rain does come, it might be a flash flood – or the rain may evaporate as soon as it reaches the ground. But even in deserts, some plants flourish. These plants have evolved different solutions to the problem of getting water.
A species of acacia found in the Kalahari Desert in South Africa has roots that can go down as deep as a twenty-five story basement – that’s about 100 meters down.
The cactus takes a more superficial approach. Cactus roots spread out over a wide area so the plant can quickly absorb as much water as possible after a rainfall. The roots of the organ pipe cactus can soak up as much as 150 liters (about forty 40 gallons) of water in a day. What’s more, their roots release toxic chemicals that discourage other plants from rooting nearby.
Most plants absorb water with their roots and give off water through their leaves. Desert plants can’t afford that water loss. They tend to have tiny leaves, with tough skins to keep water inside. Consider the cactus again – with no leaves – just sharp spines. Photosynthesis occurs on the green surface of the cactus stem.
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