INTERRELATIONSHIP BETWEEN THE DIFFERENT FLOWER PARTS DURING EMASCULATION-INDUCED SENESCENCE IN CYMBIDIUM FLOWERS

In Cymbidium flowers emasculation by removal of the anther cap and the pollinia, led to rapid colouration of the lip and advanced wilting of the petals and sepals. The ethylene production of whole flowers showed an emasculation-induced early peak in ethylene evolution followed some days later by a second increase concomitant with the wilting of the flower. In non-emasculated flowers the ethylene production increased later and simultaneously with colouration of the lip and wilting of the petals and sepals. At all stages of senescence, the contribution of the lip, petals, and sepals to the total amount of ethylene produced was negligible.Parallel to the increase in ethylene production of whole flowers, an increase in 1-aminocyclopropane-l-carboxylic acid (ACC) and malonyl-ACC (MACC) in the central column and, to a lesser extent, in the ovary was observed. Also an increase in internal ethylene concentration was demonstrated and this, in contrast, was apparent in all the different flower parts. The activity of the ethylene-forming enzyme in lips, petals, and sepals showed an increase after emasculation and such an effect could also be induced by treatment of isolated lips with low concentrations of ethylene.The data indicate that senescence in Cymbidium flowers is regulated by the central column and perhaps the ovary and that both ACC and ethylene may play a signalling role in inter-organ communication. © 1990 Oxford University Press.