FACTORS INFLUENCING FLOWER BUD ABSCISSION OF POTTED CAMELLIA

It has been a serious problem that flower buds of camellia ( Camellia spp.) drop very easily when they are grown under unfavourable indoor conditions. To examine the factors affecting flower bud abscission, some cultivars of potted camellia ( Camellia japonica L.) moved to various indoor conditions from greenhouse after flower buds were well developed. In general, double flowering cultivars showed more flower bud abscission than single flowering cultivars. Relative humidity (RH) severely influenced flower bud abscission. In `Beniodome' camellias, flower bud abscission reached to 90% under arid condition (30% RH) which resulted in very poor flowering (8%), whereas flower bud abscission recorded only 5% under humid condition (80% RH) which resulted in abundant flowering (90%). Flower bud abscission of camellias was little influenced by light intensity. Plants applied with 500 ppm ethephon produced a lot of ethylene and abscised all flower buds within a month. Ethylene accelerated the development of the abscission layer of camellia pedicels. Spray with 2 mM silver thiosulfate (STS) effectively prevented flower bud abscission of potted camellias. Polygalacturonase activity of abscission zones was correlated with the increase of flower bud abscission in camellias.