THE ROLE OF ETHYLENE AND POLLINATION IN PETAL SENESCENCE AND OVARY GROWTH OF BRODIAEA

Unpollinated brodiaea (Triteleia laxa Benth.; syn. Brodiaea laxa) flowers produced no measurable C2H4 during their entire lives. Treatment with C2H4 (0.03-mu-l.liter-1) induced senescence of open flowers, completely inhibited opening of buds and petal growth, and promoted ovary growth. Silver thiosulfate had no effect on flowers kept in air but counteracted the effects of applied C2H4. The effect of C2H4 on ovary growth seems to be indirect, via promotion of petal senescence and mobilization of the petal's metabolites to the ovary. Brodiaea flowers are protandrous; the stigma appears to be receptive (as judged by a pollination-induced burst of ethylene synthesis) only when the petals start to senesce. At this stage, papillae on the stigma surface elongated and separated.