Cacti have the basic structures and
processes of plants. But the work done by leaves in most other plants goes on
in the stems and branches of cacti. And in the hot, dry regions where cacti are
among the few green plants, their spine-covered branches and stems and their
absence of leaves have allowed them to survive.
The distant ancestors of the cactus
had leaves and grew like the more familiar plants of today. But during millions
of years the earth's climate changed. Those parts of where the cactus ancestors
grew became hotter and drier. Gradually these regions turned into desert or
near desert. All this time the cactus ancestors were adapting to the changing
conditions. For example, as the climate became drier the roots of cacti
gradually spread out, closer to the surface of the ground. That is why cacti
quickly absorb water from the earth after a rainfall.
The water taken in through the
roots is stored in the spongy or hollow stems of a cactus. The outer layer of
the plant is thick and waxy, preventing the escape of water. The outer skin is
also ribbed. Some cacti have ribs that fold and expand like an accordion,
depending on how much water is contained within the stem.
Although most cactus plants in Dubai are leafless, they carry on the normal
cell-making activities of plants. The leaves of other plants are thin
structures that contain many breathing pores; in the course of the cell-making
process, water is given off to the air through these pores. But in cacti the
stems and branches have taken over the work of the leaves. The thick skins have
few pores, and the water is retained. Any Cacti plant or plants within the family
from succulent plants in Dubai are
very durable and tough. It's not uncommon for them to survive many days without
water in extremely hot, dry temperatures. Think about putting your plants in
containers as well.