How do cactus plants adapt to such extreme weather and survive?

Answer 1

Cacti have adapted to extremely arid and/or semi-arid hot environments.

They show a wide range of features which conserve water.

Their stems have adapted to become photosynthetic and succulent, while the leaves have become the spines for which cacti are well known.

The bodies of many cacti are thick and have water-retentive tissue

Most cacti have a short growing season and long dormancy.

They also have the ability to form new roots quickly. Two hours after rain following a relatively long drought, root formation begins in response to the moisture.

Answer 2

Cactus plants adapt to extreme weather and survive, because of their survivalist body parts and functions. They're built to conserve energy, water, and work. Most herbaceous plants use their below ground roots for anchorage and storage. They use their above ground shoots for transportation of body fluids and products, and for the photosynthetic interaction with sunlight.

But a cactus is set up to minimize the amount of energy lost in shuffling back and forth between above and below ground body parts. It does so by specialization of labor. For example, the stem takes over moving, processing, and storing water, nutrient solutions, and photosynthetic products. This puts everything that's needed for life sustaining activities exactly where it's most needed, in the shoots.

In the way of another example, the breathing pores, or stomata, of most herbaceous plants are found on the leaves. On the cactus, they once again are found exactly where they're most needed, on the stem. The leaves instead are modified into thorns, spines, spikes, quills, prongs, needles, hairs, or bristles. The modified leaves aren't distracted by having to control water loss and regulate gas exchange. Instead, they concentrate on defending the stem against predators and on directing any available moisture down to the ground, to be taken in by the water table or by the plant's roots.