Water Uptake. The rate of water uptake declined sharply
approximately 4 hr after gassing the inflorescence with 2 or 20
,ul/l ethylene (Fig. 1) and stabilized at about 70% of the control
value. Wilting was observed between 6 and 7 hr after ethylene
treatment. Flowers gassed with 0.2 ,ull ethylene showed a decline
in water uptake beginning in 12 hr but these did not wilt.
Carbon dioxide inhibited the ethylene-induced decline in water
uptake and wilting (Fig. 2). Water uptake was slightly lower in
the presence of 4% CO2 which may be attributed to closure of
stomates on the flower sepals. The fact that CO2 negates the
decline in water uptake induced by ethylene places this ethylene
response in the same category with a long list of other ethyleneinduced
responses found to be reversibly inhibited by CO2 (4). It
has long been recognized that CO2 delays wilting of carnations
(14).