Abstract
Ph.D.
The sensitivity of Petunia hybrida flowers to the plant hormone ethylene
increases during the early stages of senescence and directly after
pollination of the flowers. During these early stages .of senescence,
ethylene production is very low and only increases after ethylene
sensitivity had already increased. The increase in ethylene sensitivity is
due to the forming of short-chain saturated fatty acids that accumulate in
the petal tissue during the early stage of senescence. Following
pollination, these acids are formed in the stylar tissue and transported to
the corolla where it causes a rapid increase in ethylene sensitivity. The
synthesis of short-chain saturated fatty acids is controlled by the enzyme
acetyl-GoA carboxylase. As the acitivity of this enzyme decreases, the
concentrations of short-chain fatty acids increase due to the lack of
malonyl-GoA required for chain lengthening. During the early stages of
senescence, the activity of this enzyme decreases simultaneously with an
increase in short-chain fatty acids and ethylene-sensitivity. The results of
this study indicate that acetyl-GoA carboxylase is a key enzyme involved
in the control of ethylene sensitivity in petunia flowers.