Scientists once considered plants to be very passive. However,
that view has changed, particularly within the last couple
decades. Instead of being passive, we now recognize that plants
respond to their surroundings and alter their behavior and
activities as situations change. Over millions of years, theyíve
devised a number of self defense strategies to cope with
specific challenges in their habitats. These plants have learned
to employ both physical and chemical means of self protection.
Spines serve many purposes. First and foremost, they deter most
casual herbivores from preying on the plants. In sunny dry
climates, the spines can also help the plants to survive. In
many species, these serve the same role as leaves on other
plants and carry out photosynthesis. In addition, spines provide
some shade to the plants as well. Bristles and sharp teeth on
cacti and succulents serve the same purpose as spines by arming
the plants against attack. Like many other kinds of plants, some
of the cacti and succulents al