Plant hormones are signaling molecules that are produced in one tissue of an organism
and then transported to another tissue to generate a response in cells and tissues. The multiple
plant hormones are present in almost all parts of plant growth and development, working either
alone or in conjunction with another hormone. Auxin (indoleacetic acid) promotes stem
elongation, root formation, fruit development, and brings out apical dominance. Cytokinins
stimulate cell division and germination. Gibberellins stimulate stem elongation, seed
germination, and fruit growth. Brassinosterioids promote cell elongation division, seed
germination, and xylem differentiation while inhibiting phloem differentiation. Abcisic acid is a
plant inhibitor, slowing growth, maintaining dormancy, and closing the stomata during stress.
Another hormone like abcisic acid is ethylene, which promotes fruit ripening and the triple
response, which involves a slowing of stem elongation, thickening of the stem, and growing of
horizontal stems (Campbell and Reece, 2008).
An example of plant hormones working in conjunction with another can be seen in plants
with different ratios of cytokinins to auxins present. In plant cells with only cytokinins present,
only cell growth will occur, but as auxins are added, both cell growth and division occur. Auxin
and cytokinins also collaborate in controlling auxiliary bud inhibition. More illustrations of plant
hormones cooperating include the partnerships gibberellins make; both gibberellins and auxin
must be present in order for fruit to develop, and the ratio of abcisic acid to gibberellins
determines whether a seed will remain dormant or germinate (Campbell and Reece, 2008).
Gibberellins, the main focus of this research, are found on the meristems of apical buds
and roots and young leaves (Campbell and Reece, 2008).There are multiple types of gibberellins,