The complexities of the interactions these five
plant hormones have are still not fully understood,
though large portions and sequences are known.
The combination and levels of each hormone are
different for each plant species and at each different
stage during their respective developments. For
example, auxins, gibberellins, and cytokinins are
all synergistically involved in the setting of most
fruits. Individually, each may be able to initiate
the process but cannot see it through to completion
without the assistance of the other two hormones.
Abscsisic acid is thought to also play a role in fruit
development, but its exact role in the process is not
yet known for sure. In other interplays, abscisic acid
is produced in concert with ethylene even though
their purposes are contradictory in regard to fruit
ripening and drop.
Do Plants Really Have HORMONES?
There is much debate and has been for some
time in the botany world about the actual term
“hormone” when referring to plants. While no
one reading this is likely to pound their fists on
their breakfast tables demanding to know why
this has not yet been resolved, there are several
compelling reasons as to why this clash exists.
Some botanists and plant scientists suggest that
the term “plant growth substance” is more apt.
The rebuttal to that phrase is that “substance”
is too vague a term. Those that want to do away
with calling them hormones argue that, unlike
hormones in mammals, plant hormones often
serve contrary functions that don’t have a parallel
in the animal world. For example, a plant will
produce both a substance that will cause it
to grow and a substance that causes it to go
dormant or even die. There is not such a conflict
of roles in the world of animal hormones. These
researchers claim that scientists are trying to
make these substances fit the mold or definition
of a