Effects of Temperature and Ethylene Response Inhibitors on Growth and Flowering of Passion Fruit

This study examined the effects of different day/night temperature regimes or silver ion on growth and flowering of passion fruit 'Tai-nung No.1'. Low temperature treatment ($20/15^{\circ}C$) caused passion fruit cultivar 'Tai-nung No.1' to fail to flower. Flowering induction occurred within a temperature range of $20-30^{\circ}C$, with no significant difference in the days to first flower bud and the total number of flower buds between plants grown at $30/25^{\circ}C$ and $25/20^{\circ}C$. However, plants grown at $30/25^{\circ}C$ exhibited their first flower buds set on the higher nodes and had higher abortion rates of flower buds than those at $25/20^{\circ}C$. Plants grown at $30/25^{\circ}C$ had the most rapid growth and the shortest plastochron. We also evaluated the effect of the ethylene response inhibitors silver nitrate ($AgNO_3$) and silver thiosulfate (STS) on growth and flowering of potted passion fruit 'Tai-nung No.1', when they were exposed to low temperature conditions ($20/15^{\circ}C$) following chemical treatments ($AgNO_3$ or STS, at 0.5 or 1.0 mM). $AgNO_3$ and STS treatments induced flower formation and initial flower bud formation within approximately two weeks at $20/15^{\circ}C$ whereas non-treated control plants exhibited no flower formation. ACC content and activity of ACC oxidase in the leaves of passion fruit 'Tai-nung No.1'exposed to low temperature conditions ($20/15^{\circ}C$) were significantly inhibited by the ethylene inhibitor treatments. These results indicate that ethylene, which is produced under low temperature conditions, plays an important role in inhibiting flower formation in passion fruit.