Cactaceae are perennials usually bearing areolas
and can withstand drought due to their succulent
stems, which contain water storage tissues in
their stems.
Cactaceae contain areoles (modified lateral shoot
and structure that bears spines) and buds that
eventually turn into flowers then fruit. The areole
is usually located on the tubercle (projection
from stem to surface) and its adaptation is essential
since the spines are located there.
The spines (modified leaf) are identified in two
groups, the central spines (located on centre
of areole) and radial spines (located around the
margin of the areole. The spines serve various
functions; the most fundamental being the protection
from predators seeking food or water from the
cactus and the other being the absorption of atmospheric
water, which the spine distillates it into water
droplets, thus resulting the water droplets to
fall into the soil where the water is absorbed
by the cactus' shallow root structure. The wide
and shallow root structure allows the cacti's
to absorb water more rapidly particularly through
arid phases where water evaporates almost immediately.
During extensive phases of drought, the distal
portions of the roots remain accessible to water
and the rapid growth of the roots generates additional
root hairs.
The cactus' vibrant blooms and
aroma draw pollinators.
Cactaceae encompasses dense and thick outer tissues
and cuticles, allowing the cactus to seal off
its external environment resulting in the reducing
the loss of water and the outer component (waxy
cuticle with water proof covering) forbids the
carbon dioxide to defuse into the body of the
cactus, thus the storing of carbon dioxide from
night to day is a special feature of succulent
plants called "succulent metabolism".
The entire stem of the cactus consists of water-storing
parenchyma, packing tissue, thus 80%-90% of the
cactus is water. Cacti's can endure a water loss
of around 60%!
